Re-live your trip in Google Earth

How to use StarTraX on the Web - a comprehensive description of the features of StarTraX

Getting Started Getting StarTraX loaded and ready to replay your track file will be your first priority.

Controlling the replay How you use all the buttons and controls that allow you to manage your track replay.

Making the replay realistic Some of what goes on "behind the scenes".

Track Information A reference section about the information available about your track.

Gliding features If your sport involves un-powered flight then this section will be of interest to you.

Flight tracking (experimental) Watch real-time tracks of commercial aircraft in StarTraX.

Usability This section brings together a bunch of features that have been developed to make StarTraX easy and intuitive to use.

Release History This is where we document its development.

Getting Started


StarTraX is a real-time GPS track animator which works through the amazing Google Earth, allowing you to relive your GPS journey in real time. It is provided as a domestic entertainment system.

StarTraX runs in a browser on "standard" Apple Mac and Windows computers and laptops using some additional software tools from established international companies. If the software is not already installed on your computer, you will be guided through the installation when required. See Requirements here

Security and privacy

Access to your data

One of the software tools you will be installing is "Java", which gives StarTraX access to the data on your disk drive. You will be asked to agree to a number of things relating to security and certificates that you may never have thought about in the past but which are really quite important.
We personally assure you that we have no interest in damaging your computer or stealing your personal information. You have accessed StarTraX through our web site, and you can contact us at to verify our bona fides.

Collection of data

In our continuing efforts to improve StarTraX, we collect information about which version of software you're using to access StarTraX and statistics about which StarTraX features you use.

Interactive Site Map

Click in the image to explore the details, use your browser's "back button" to return.


You access StarTraX by visiting (pointing your browser at) our web site at

Why the complicated name? The domain name, "" is derived from "GPS" and "Animator" because we animate (bring alive) GPS tracks! We would have liked a simpler name, but unfortunately all the obvious name choices were already taken.

Log in

The first time you access StarTraX, you are presented with the Log in page where you enter your email address and the free Registration Key that you received after completing the StarTraX Registration page. You will also be presented with the log in page whenever you access StarTraX from a new browser session and after every 24 hours.

Please read this page regularly because we use it to announce important information that may be of interest to you.

Initial load

Once you are logged, in the main StarTraX page opens and loads Google Earth.

StarTraX loaded, and loading Google Earth

The "busy" indicator is displayed on the main page to let you know that StarTraX is busy working in the background. Here, it is alerting you that it is Loading Google Earth. Please wait.... When the computer is particularly busy, it slows down or stops spinning altogether.

Loading Google Earth can take a few seconds, and When Google Earth is loaded, you are invited to

Now 'GO TO' a track file

As soon as Google Earth is loaded, StarTraX "pops up" the "Go To" page. This is one of the many places where StarTraX uses "pop-up" windows, so you must DISABLE your browser's "pop-up blocker" - at least for the domain.

Track Selection - the "Go To" page

You can Select a track file to replay... at any time by clicking the Go To button from the StarTraX main page which allows you to select a track file from a number of locations.

The "Local track files" and "Demonstration tracks" sections will always be displayed.

The "Scenery Tracks" and "StarTraXLogger" sections will only be displayed if you have activated those features as described below.

Local track files

We have provided a choice of two ways to open track files that you have saved previously to your computer.

These are: "gpx", ".igc" and "plt".

This rather complicated approach is imposed upon us by the by the need to protect you, your computer and the private data on it from malicious hackers. The underlying reason is that scripts running inside browsers on your computer are, for good and valid security reasons, prevented from accessing data on that computer. There are plenty of unscrupulous operators who would exploit such a facility if it were not rigidly prohibited.

Browser open

With this approach, you are invited to select a track file from your computer. That file is uploaded to our web site where we massage into a form that can be used and sent back to your computer.

Java open

For this feature to work, you have to have Java 1.6 or later installed on your computer and Java enabled in your browser. Follow this link to learn about Java. This way, you are clearly warned that the software (StarTraX) is going to access data on your computer, and you have to explicitly grant permission to do this. As we said earlier, we personally assure you that we have no interest in damaging your computer or stealing your personal information. You have accessed StarTraX through our web site, and you can contact us at to verify our bona fides.

We have implemented a fairly complex strategy, by developing a "Java applet" that is invoked by StarTraX. Unlike browser scripting languages, Java is able to access your data, but only after providing you with a clear warning and opportunity to manage your own data security.

This button opens a familiar dialog box displaying file types that it can process.

Demonstration tracks

Demonstration tracks - click to choose  Here is a small group of track files that demonstrate some of the features of StarTraX. They are stored on our web site and are downloaded to your computer when you click on the Radio Button next to the file description.

Scenery tracks

This section will only be displayed if you have selected a Scenery file from the settings page that contains a named KML lineString

If your file contains KML "lineString" features, they will be available as tracks in the track selector opened by the GoTo button. For this type of track to be available in StarTraX, the linesString feature in the kml file must have a value in the attribute.

This is not a requirement of kml, so if your file contains lineString features without a name, they will not be playable in StarTraX.

This list shows all the named lineString features in your scenery kml file, sorted in alphabetical order.

As the kml feature contains no time stamps, you can supply your own speed to follow those tracks. It defaults to a value of 20.

StarTraX Logger files

This section will only appear if you are using the StarTraX GPS Logger phone app). It will list the track files that you have recorded on your phone which are now stored on our web site. They are listed in reverse time order, with the latest track file on the top. The tracks are identified by being named with the date and time they were created.

Click on the Radio Button next to the track file to replay a track.

Click on the track name to download the track to your computer.

You can also open multiple track files simultaneously using the "Multi track" feature.

Running StarTraX

Once you have selected a track file, StarTraX loads the file and sends Google Earth to the location.

For the few moments that Google Earth requires to download the imagery of the area of your track it displays  Imagery loading progress...

Your track is now displayed in a small window where you can zoom in and out and navigate the world with your mouse buttons to see your track displayed in a session of "Google Maps".

Once the track file is loaded, it announces Track(s) Loaded. and your GPS track is displayed in Google Earth

At this time the Replay Controls are also displayed, allowing you to start and pause the replay.

You can also navigate around the world in Google Earth using the Google Earth Navigation controls or your mouse. Full instructions can be found at Google Earth Support

Note the Google Earth "Street View" stick man is available, so you can jump into Street View whenever the replay is halted

When your track file is loaded, your GPS track is displayed in Google Earth as a series series of numbered dots joined by coloured lines. The dots represent every tenth point recorded in your track file.

Select start point

By default, once you have loaded a track the Start Button will start the replay at the first point in your track file.

You can choose to start at any point by clicking on a point on the track.

StarTraX then displays details of the Selected point and invites you to click on the Start animation from here. link.

Replay Controls

You can press the Start/Pause button to Start or pause the replay. StarTraX starts to interact with Google Earth and begins the animation. The Start/Pause button now displays , and, when pressed, will pause the replay, allowing you to explore the Google Earth image with the Navigation Tool which is not available while the animation is running.

By default it starts the replay at the first point in your track file.

Track Progress Indicator

Track progress indicator. Move the pointer to where you want the replay to re-start. You can "drag" the pointer to re-start the replay at a new time. As the replay progresses, the pointer moves along the bar and the local time of the current replay is displayed under the pointer.

Fast forward display speed

You can Control the replay speed. Increase the replay speed (256 is the maximum). with and Reduce the replay speed (minimum is 1 - normal speed). with .

Each click doubles or halves the previous value. A minimum of 1 and maximum of 256.

The higher the replay speed, the faster the images have to be displayed. This will inevitably result in some loss of clarity.

Track line colors

The line coloring indicates the speed that you were going at the time. The colors are explained in the Color Codes box which can be displayed by hovering the cursor over the Colour legend icon. Under the heading Colour Codes the speeds of Up to and Over are displayed in color.

The choice of colors is automatically assigned and the choice of break points is calculated from the speed data in your track file using simple statistical methods. You can refine the choice of colors and break points to display your own choice of colors and break points by using the Color picker option in the "Settings" menu

It now generates a model appropriate to the theme it identifies from your track in Google Earth representing the position of a "Target Point" which moves along the track in real time.

Your viewing point moves with the model, giving you the effect that you are moving through Google Earth's world as if you were attached to the model.

At the end of your track the replay will stop. If you try to re-start at the end, it will alert you with End of track - re-select a start point.

Controlling the replay

The settings button will Open the main settings menu from where you can customize your replay options... whose descriptions you can access by clicking on the links below.

Time Zone


View Mode

Start Point

Disp Dists.


Show Compass?

Hide track when running.

Time Slider

Smooth Track

Smoke trail length

Colour the track by:

Display Details


Cockpit Instruments

Calc. Wind

Show Wind

Show Clouds

IGC Altitude source

Control the view position with mouse or buttons

When describing the viewing position we refer to a camera which is effectively recording the 3 dimensional (3D) world and presenting it on your computer screen in 2 dimensions (2D). So, whenever you see a Google Earth scene, it can be thought of as having been taken by a camera positioned at a certain location (latitude and longitude), at a certain altitude, facing in a certain direction (North, East, etc), with a tilt in a number of degrees above or below the horizontal, and with a roll angle, where the camera is rotated along its centre axis.

You can control the location (latitude, longitude, altitude) and orientation (heading and tilt, but not roll) of the camera in StarTraX with either the buttons or the mouse. In all cases, when the animation is running, StarTraX will endeavour to keep the target point in the centre of the screen. In practice, this is not always completely achieved due to the competing pressures of calculations.

There are three sets of buttons which allow you to control the position of the camera:

  • Range: the distance of the camera from the target point. You can Move closer to the target point. with and Move away from the target point. with The initial value is set at 50 metres. Each successive press of the button moves the camera in or out by about 30% of the current value.
  • Heading: Allows you to look around to the left or right as the animation progresses. Move your view in the direction to the left. with and Move your view in the direction to the right. with Each click of the button increases or decreases the angle by 15 degrees per click
  • Tilt: The up/down buttons control your viewing angle in the vertical plane above the current track segment. Look up to the target point. with and Look down on the target point. with .

    It defaults to 15 degrees above the track segment and can be changed in the range of 0 degrees, along the track to 90 degrees, straight down and -90 straight up.

Control the Camera with the Mouse

In addition to the camera control buttons described above, you can also control the camera with the mouse using gestures similar to those provided in Google Earth. They rely on you having a mouse equipped with a mouse wheel.

The camera mouse controls work with your cursor is within the camera control panel.

When active, the cursor is displayed as a "crosshair" while you are using the mouse to control the pan and tilt of the camera.

  • Pan left and right With the mouse wheel pressed, move the mouse left and right.

  • Tilt down and up With the mouse wheel pressed, move the mouse forward and back.
  • Zoom in and outRoll the mouse wheel forward and back to zoom in and out.

Four view modes

The four view modes allow you to Control the way the camera follows the target point.

Smoke trail length

You can modify the dissipation behaviour of the smoke trail with the Smoke Trail length buttons


Position above and behind the target point. Stay in line with the direction of travel. In this case, the observation position and orientation remains in line with the direction of travel.


Follow the target point but fix the direction of viewing.

The "Observing" mode was specifically designed to follow a glider or paraglider's track, which tends to follow a circular track as the pilot strives to stay in the thermal.


Lock the camera on to the target point so you see the the target point's view. You can still change the camera's orientation, swinging the view left and right, up and down with either the mouse or the buttons, but you can't move in and out the camera position remains fixed relative to the target point


In this mode, the camera does not follow the target at all. You must use Google's navigation controls to follow the track. This option is not recommended for normal use.


When StarTraX loads a track file, it makes a model selection based on the theme it deduces from your track. These models have been selected from Google Earth's huge "warehouse" of models that enthusiastic virtual model builders have been constructing and providing for our enjoyment. It's at if you want to check it out.

The Models menu enables you to make your own model selection.

This list is populated from our web site ( when you start your StarTraX session, so we will add to it as we find new and more amusing models to play with.

You can play to your heart's content with these models they are downloaded from our web site as you select them, and you can play with them as you like. You can put the 747 on a ski-field or go flying with the yacht!

We are deeply indebted to all the enthusiastic model builders for this rich resource of models.

Here are some of my favourites:

The ME109

the Audi Le Mans

The 747

Include your model

If you build or find a model that you would like included, send us an email containing link to the model and we'll consider it for inclusion. We have to do a bit of work on most models before they can be included.

If you are building or manipulating models for inclusion in StarTraX then the following tips will make our job a little easier:

Model type: Google Sketchup (.skp)

Orientation: have it facing towards the green axis, so that in its normal position it is going away from you.


a)      positioned with vertical axis through the viewer's position with vehicles, this is the position of the driver's head.

b)       Positioned with the base of the model (wheels) on the ground

Scale: realistic. Some models are scaled very small or very large

We calculate, store and use a value of the height of the pilot's eye above the ground for each model

Multiple file formats

GPS track data is recorded in many different formats depending on the model of GPS receiver and the software provided to transfer the track data from the GPS unit to your computer. We have taken a conservative path and have settled on just three standard formats:

If you have a format that is not in the above list, you can use GpsBabel to convert it to gpx and StarTraX will happily process it.


For those of you who engage in your activity with GPS-equipped friends or competitors, you can now replay all your tracks together in StarTraX.

To access this feature, you first place the track files that you wish to simultaneously replay in a single folder on your computer's hard drive. You then click on the Multi-track check box in the Settings tab of the Menu option. This will Enable multiple tracks to be displayed together.

When checked, the Go To page displays the message Multi-tracking. Select multiple files. to inform you that the facility is enabled:

"Open Local files" dialog box allows you to select multiple track files with familiar mouse gestures:

As you select track files, the file name is added to the list of selected Track(s) Loaded. , along with the track name (if supplied in the track file):

When you click the button, StarTraX reads the files one by one and presents them in the Google Earth window.

You might have to be a bit patient here as there's heaps of work going on in the background to calculate the position of the points and display them in Google Earth.

The tracks are separately colored and are labelled A, B, C etc.

The feature has been developed primarily for paragliders, and will load a different colored paraglider for each track.

Not that it's likely to bother you, but there's a limit of 26 on the number of files that can be opened concurrently.

Synchronize the tracks

When multi-tracking, click the Synch. link to Synchronize the other track(s) to pass nearest this point at the same time. It looks through each of the other tracks for their point nearest to the selected point. It then applies a time offset value (displayed) to the track to cause the new track to re-start at this point. This facility may be useful if you want to compare multiple performances around the same course.

When the tracks are synchronised, the Unsynch. link will allow you to Reset tracks time stamps to remove synchronization and return to the original values.

Multiple tracks in a file

Some GPS software generates gpx files containing multiple, separately named tracks.

When you load one of these files into StarTraX, it detects the presence of multiple tracks and presents you with this StarTraX Track Selector. File selection. Your track file contains a number of individual tracks. Select a track from the list below. with the instructions: Select a track from the drop-down list.

The track file name is displayed ("25-SEP-10" is the file name in the example) along with the name of each track in the file.

You can select a single track and press the button to load that track into the relpay.

Track smoothing

Apply smoothing to your track to turn sharp turns into curves. GPS track data consists of a set of points recorded in your GPS at its own time intervals. GPS tracking is also only accurate to a few metres, so if you can record at high speed, you get high-speed zigzags, and if you record at low speed, you get further spaced zigzags.

With Track Smoothing activated, we take your points and generate up to nine new points between each of yours, to form the sweet curve that you see below. The new points are just as "honest" as the original points as the new track still passes exactly through each of your recorded points. We have just eliminated the sharp corners.

Turns this plotted hang glider data

into this smoothed track


Or this ski track


Into this:


StarTraX uses an algorithm to deduce a 3rd order polynomial for a line between the second and third points in every 4 point sequence in the track, using the first and third segment to provide a starting and ending gradient.

It then generates up to nine new points along that line and add them to your track (with appropriate time stamps and altitudes). The number of points depends upon the time interval between your points, and is determined to result in new intervals of around 1/2 second.

This is all done between loading the file and starting the replay, so it doesn't impinge on run-time performance at all, however it does impact on the time taken to load the track file.

In extreme cases, with complex track files or multiple track files, this may overload the capacity of your computer and cause it to hang or crash.

It took me a long time to find an appropriate approach to the smoothing task. Much of the material published on the web relates to "splines", which did not suit my needs as I was determined that the smoothed track would be as "honest" as the original track and would therefore have to pass through all the original points. The spline solutions provide a nicely smoothed track, but they do not religiously go through the all the original points.

I am indebted to a sailing mate who, as a nautical engineer, had an old textbook on computer methods for ship surface design. It contained the following page describing and detailing a Fortran subroutine it must have been 30 years old!

I still don't really understand the method but I converted to Javascript and implemented in StarTraX and after extensive testing, I'm satisfied that it does a good job. Thanks Malcolm.

Units of measure for distance and speed

Choose your preferred speed and distance units.

Different nationalities and different activities call for different units of measure of distance: kilometres, statute miles, nautical miles, feet and metres. These different distance units influence the derived values for speed: kilometres per hour, metres per second, miles per hour, feet per minute, knots.

The Units "drop-down combo box" allows you to select the units in which speeds and distances are displayed







Google Earth


km. and metres




metres/ kilometres


nm. and feet






m. and feet





This setting also changes the units Google earth uses when displaying altitude and distance when StarTraX is Paused. The screen shot below shows an example of the display when Metric units are selected.

And again, when Nautical is selected:

Time zone deduction and manual override

StarTraX deduces your time zone from your longitude, change the time zone in hours +/- UTC. It assumes that the time stamps in your track file have been recorded in UTC (GMT).

It deduces the local time zone from the longitude of the track (actually just the first point) and displays the GPS time (File:) and local time (Local: ) in the point display and the display window. It calculates the time zone by working out in which 15 degree segment of longitude the point lies, and adds or subtracts one hour for each segment. (360 degrees / 15 = 24 hours)

It makes no allowance for Daylight Saving time or for local time zone variances. You may override the calculated time zone by entering a new value in the Zone entry field box.

If you are playing a track that was recorded in a different time zone than your PC is currently in, then GE will calculate the local time based on your current location, not the track's location.

Un-timed tracks

If StarTraX detects that the loaded track file contains no timestamps, it will offer you this option: Un-timed track - what speed would you like? which gives you option to replay the track at a speed of your choice in your currently selected speed units.

Type in a positive number.


You can add scenery features to your model of the world.

Google Earth layers street, buildings, borders

The check boxes allow you to turn on or off the three native layers in Google Earth. By default all three are turned off.

The only reason you might want to change these settings would be if your view was too cluttered, or if the loading of the layers slowed down the performance.

Roads Layer Show the position of roads.

Borders Layer Show 3D buildings.

Buildings Layer

I'm particularly impressed with the ski terminals and lift towers displayed at Whistler:

Included scenery

In the Scenery kml files section you can either import some scenery files that we have assembled from various sources or you can load your own.

These are scenery files we have found on the internet or generated ourselves. If you have any files (kmz, kml) you would like incorporated, email the file(s) or their URL to us (at and we'll include them. The files are downloaded by StarTraX from our web site at run-time, so no software update is required to deploy an update. We have assembled a small (but hopefully growing) selection of scenery that you might enjoy. If you navigate (via the GE side of StarTraX) to their areas, you will see them displayed. They are mainly ski-runs and lifts.

We acknowledge the unauthorized use of some excellent scenery files that we located on the web site in this feature.

Local files

You can also  Select a kml file from your local disk drive to display in StarTraX. by selecting the Local button and navigating to your file.

At this stage we only handle kml files, not kmz.

You can Show or hide the scenery layer from the Show Scenery Layer check box:

Surface(Aerial)? override

You will only need to use this control in the unusual circumstance that your track encompasses both aerial and surface components, or if StarTraX is unable to determine the nature of your track and you wish to Switch the track style between being "in the air" and "on the ground". . I have a track that includes the flight to the ski fields (aerial) and the day skiing (surface). StarTraX struggles to determine whether you want to view the aerial or surface component of the track. This check box allows you to override StarTraX's determination and display the track on the surface or using the altitude recorded by your GPS (aerial).

Making the replay realistic

This section describes features over which you have no direct control which make StarTraX a realistic replay experience.

Google Earth interface

StarTraX relies entirely on the truly amazing Google Earth to display your moving track in 3D space. In mid 2008 they released a new and powerful method (the Google Earth API "GEAPI") for programmers (like me) to interact directly with the GE globe and have regularly released enhancements and improvements to the interface. And of course they continue to release more and more detailed imagery on a regular basis.

This has provided an amazing 3-Dimensional space for developers like me to play in. We don't have to worry about so many of the complexities of working in a 3D space maps, land form, ground texture, scale and projection of a 3D world on a 2D computer screen. This is all handled by GE, all we have to do is to tell GE to put our model aircraft at a certain location (latitude, longitude, altitude) and show it as if from a camera positioned at a certain location, pointed at the model. The underlying language used for sending these instructions to GE is called KML whilst the interface to the KML is via the Google Earth API

So, what you see in the right hand pane of StarTraX is entirely courtesy of Google Earth: the landscapes created from satellite photography draped over an underlying structure of ground contours, with layers of streets, borders, town names and 3D buildings with your 3D avatar appropriately located, scaled and oriented in the landscape.

Progresses in real time you see your trip as it happened

At run-time, your position and the camera position are re-calculated around 60 times a second based on your previous position and your current speed and direction. GE is then instructed to move the target model and the camera to the new point. GE then has to re-draw the scene based on these new positions.

Smooth camera pan and tilt

Because the GPS track is a series of points, the track you see is a series of straight lines linking the points. This means that after the camera has followed the target along one segment, it has to re-position abruptly to follow it along the next segment. With small direction changes this wasn't a problem, but with large ones especially when the track is a glider orbiting in a thermal, the abrupt camera position changes led to some very abrupt changes of view.

In earlier versions we were relying on GE to provide a smooth transition from one camera position to the next, but this was not always effective, so we now control these camera transitions by anticipating the next segment turn and tilt angle and start to move the camera into the next position at the start of the segment, so that once the target has reached the start of the next segment, the camera has been swung into position for this next segment.

we link the camera panning with thermalling (gliding in climbing orbits). When thermalling, the camera pans continuously, at a rate determined by the turn angle. When not thermalling, the camera pans at a fixed speed, starting later in the segment, just in time to get the orientation correct at the end of the segment.

Realistic banking

Whilst generating the smooth track above, we can also work out the G-force that would have been generated in the turn and have visually represented it by banking the model appropriately. So now when the paraglider turns into the thermal, or the skier carves into a tight turn, you can see the model doing exactly the same thing.

The above shots were taken whilst in Observe mode. When in Follow mode, the camera also banks, providing a realistic replay. We have drawn in the horizon in the shot below to emphasise the point.

Calculating the angle of bank (roll) from GPS track data.

The roll angle is derived by resolving the gravitational and centrifugal forces on the body, whether an aircraft, glider or skier, as it follows a curved path.

The calculation requires three (3) points in order to determine the roll at the second point.

Step 1 is to calculate the radius of the circle defined by the three points P1, P2, P3 using the algorithm described in

Care has to be taken to ensure

  • the correct sense of the roll angle and
  • the handling of straight segments which have an infinite turn radius.

Step 2 is to calculate the roll angle using the speed of the aircraft (v) (at P2), the radius of the circle (r) and gravity (g) as tan(θ) = v2/gr (see )

Finally, since we are animating the model between data points, to avoid the seeing it suddenly jump from one roll angle to another, for example, from straight and level into a 45 degree roll, we introduce a roll rate, taking us from one roll angle to the next in smooth steps.

We deduce the roll rate by taking the difference between the roll angle (in degrees) at one point and the roll angle at the next point and divide it by the time interval (in seconds), resulting in a roll rate in degrees per second.

To do this, of course we need a sequence of four (4) points - two overlapping sets of three to get the roll at this point and the next point.

At this stage we could just increment the roll at the roll rate to achieve the required roll at the next point. However, over a long time interval - say 3 seconds or more, this results in a very unrealistic animation. So, if the roll rate is greater than a standard roll rate then we start the roll immediately, if not, we determine when to start to change the roll at the "standard rate" just in time to to achieve the required roll at the next point.

To do this, we calculate a "time to start the roll", at which time we start to change the roll angle at the standard roll rate.

Track Theme derived from track data

StarTraX analyses your track to interpret your activity. It determines which of the following themes that the track most closely matches. I'm not giving too much away about this process except to say that it analyses the points in the track for speed, altitude, and vertical speed and categorizes the track into one of the following categories which I have called Theme.

Whilst this works in general, it can get confused when the characteristics are not consistent throughout the track. For example, I have a track of a journey from Sydney to a ski resort in Japan, which includes two flights, a train and bus trip and an afternoon skiing. StarTraX deduced Acft-Light.




surface, walking speed


surface, faster than cycling


surface, very flat, pretty slow


surface, not so flat cycling speed


aerial, slow


aerial, fast


aerial medium speed


Acft-Light and orbiting track


surface, lots of vertical motion

It re-assesses the theme each time you load a new track. The theme it deduces is displayed in the in the file display:

Once it determines the Theme of your track it displays an appropriate model to represent your activity, like a skier, car, boat etc.

Ground altitude

If it can deduce the ground altitudes then it uses the ground altitude rather than the GPS altitude when following Surface (as opposed to Aerial) tracks. This provides a more realistic replay as the altitude that the GPS device records can often be 10's of metres above or below the ground surface that Google Earth uses in the display. Using the GPS reported altitude in these cases would cause the track to be displayed above or below the Google Earth surface.

You may wonder why we go to this effort, as GE allows lines and points to be drawn "clamped to the ground" . Well, the answer is that we do it to improve the way the camera works. By retrieving the ground altitude at both ends of each segment, we can calculate the actual tilt of the track, and position the camera accordingly. This may not seem a big issue, but it was a problem when following a skiing track down the mountain. With no actual ground altitude, we couldn't get the excitement of pointing the camera down to follow the track down a steep section.

Smooth replay tricks

A significant proportion, probably 30%-40%, of the development effort has been spent on getting a smooth replay eliminating the jerkiness from the target point movement and moving the camera smoothly.

As you probably know, movement that you see on the screen of your TV, cinema screen or computer is not actual movement at all but the display of slightly changing images in rapid succession. The frequency with which the images are displayed is called the "frame rate", usually measured in frames per second (fps). The minimum frame rate required for the human eye to perceive smooth motion is influenced by brightness, image blurring etc and is the subject of extensive study. Cinemas work at 24 fps but use image blurring to enhance the effect. TV's work at higher rates.

The challenge we faced was to complete all the calculations required to generate the next frame and have them displayed in Google Earth within the allotted time frame. After much blood, sweat and tears, we have managed to streamline the code sufficiently to achieve a frame rate of around 50 fps when running on a basic PC with a standard video card.

StarTraX doesn't run in isolation on your computer the Windows operating system is managing the computer and is allocating computer resources CPU cycles, and memory, to all the processes running on your box according to that process's priority. StarTraX runs at the highest possible priority and we assign the lowest priority to the Google Earth component, which runs as a separate process. This means that occasionally the background scenery in GE is a bit slow to refresh, but we chose that as an acceptable compromise in the search for a smooth replay.

Up to a point, you'll get a smoother replay on a more powerful computer or a higher quality video adapter. On the other hand, running on a slower computer, or one that is burdened with other tasks, like an office server or a Mac running Windows or VM, may result in degraded performance.

Track Information

This section describes features that provide you with information about your track.

Numbered points

StarTraX generates a series of numbered dot points along your track in Google Earth. The primary purpose of these points is to allow you to select a point on the track at which to start your replay. You can also right-click on these points to find out details about the track at that point.

The points are numbered from zero (the first point) and occur every ten points along your track. We discovered that putting a point at every point of your track generated a very cluttered display.

This explains that the point number displayed with the point (16 in the example) refers to point number 160 in your track.

When multi-tracking, the points are labelled A, B, C.. to Z (that's why there's a maximum of 26 tracks) and each point is painted in a different color to assist you to identify them.

Track Profile

This graphical analysis tool, which Display your track as a graph of speed, altitude etc. by time or distance... allows you to do some serious evaluation of your performance. It is launched from the button.

The initial view shows a graph of altitude against time. The blue line follows your track, the brown line follows the terrain.

You can change the values displayed on the Y Axis to Altitude, Speed or VSIby clicking on the buttons.

The X Axis can display either Time or Distance depending on your choice of button.

The Zoom buttons works a little like a camera zoom lens, increasing the magnification of the view to allow you to Zoom closer or Zoom more distant to examine your track in more detail.

Mouse gestures You can also use the mouse scroll wheel to zoom in and out.

The zoom-out is limited to displaying the entire track. The zoom- in works as long as there are at least three points in view.

The Pan buttons are most effective on conjunction with the Zoom button to Move the view left or Move the view right .

By default, the vertical pan and zoom is set automatically to display the entire data set in the Y-Axis. The Vertical controls allows you override this default setting, by clicking on the "Manual" option, to enable you to pan and zoom in the vertical axis.

When set to "Manual", the vertical pan and zoom controls become available which operate similarly to the X-Axis pan and zoom, except in the vertical plane.

The graph uses the distance units selected for the track and displays the values on the Y-axis grid-lines

To assist you to relate the graph to your track in Google Earth, In addition to the time or distance, the X-axis shows the display point number (Pt.)nearest to that grid line

Export your track to Google Earth

The full desktop version of Google Earth has some really excellent tools such as Ruler, Polygon and Path that are great for analysing tracks, and also has facilities for uploading track files in a wide range of formats (.gpx, .nmea, .plt etc.) but its ability to display tracks in the way we're used to in StarTraX is limited. So, rather than "re-invent the wheel" and try to implement these analytical tools in StarTraX, we have provided the facility export your tracks directly to Google Earth.

The "Unload KML" link unloads the currently selected track in Google Earth's KML format which can be imported directly into Google Earth, retaining the tracks current coloring (speed or VSI as selected).

There is a limit to the size of the track file that can be exported which, when exceeded, generates the "413 Request Entity too large" error.This can only be overcome by reducing the size of the track file.

After clicking the "unload KML" link, StarTrax will work with your browser to export your track file to a KML file and the browser will download the file and offer you the choice of opening it. If you have Google Earth installed on your computer with the default settings of having it open files with a .kml extension, then the file should open in Google Earth.

Flight instruments

The Cockpit Instruments check box causes StarTraX to Display all the flight instruments. when the track is playing.

Speed Indicator

The speed indicator displays your current speed in the units you have selected:

The dial is calibrated from the current track, with the green sector representing the mean or average speed of the track, with the speeds slower than average on the left ranging from magenta to blue and the speeds faster than average on the right, ranging from yellow through red.

It uses the same color coding that is displayed in the speed legend for that track.


Show the compass direction indicator overlay in the Google Earth screen. when your track is being played.

Viewing Direction

The viewing direction is indicated by the position of the rotating compass ring relative to the fixed marker.

This example indicates you are looking slightly east of North at a compass bearing of approx 20 degrees.

The compass ring rotates as you change your viewing direction.

Track Direction

The track direction is indicated by the position of the nose of the rotating aircraft symbol.

In this example the current track is about 235 degrees.

In StarTraX, all compass headings are calculated from the track positions' latitude and longitude and so are relative to true North, not magnetic North.

The track direction indicator rotates according to your track direction.


The altimeter is based on one used in a light aircraft and is calibrated in feet.

It shows hundreds of feet by the position of the "big hand", thousands of feet by the "little hand" and tens of thousands of feet by the white line.

This example is showing an altitude of 18,950 feet.


The variometer shows the vertical speed in hundreds of feet per minute.

It's based on one in a light aircraft.

The example shows us descending at 300 feet per minute.

Metric instruments

When Metric units are selected, the altimeter and variometer display metric units.

Smoke trail

The "smoke trail" is the track left behind the target point. As your model moves along its track it generates a thick line behind it, much like the smoke trail generated by formation aircraft in a fly-by. Thus the name "smoke trail". The trail is colored according to the currently selected track coloring. By default, each section of the smoke trail becomes progressively fainter until it disappears (dissipates) after five minutes. You can modify the dissipation time by using the smoke trail length control.

The smoke trails will be erased and re-started when you re-start the display at a new point, change the track coloring selection or change the distance units.

Track color

The line coloring indicates the speed that you were going at the time. The colors are explained in the Color Codes box which can be displayed by putting the cursor over the "Color Legend" box pictured right.

The colors graduate from slow, in blue to fast in dark red.

StarTraX uses statistical methods to determine the categories based on the speeds it finds in your track file.

These categories will be different for each track file and the speeds are displayed in your choice of units which you can choose as described below.

Display Details

From this menu option you can Select which details to display next to the target point. as the model moves along the track. Here I am with speed selected, skiing at 49 kph.


Don't display anything.

File Name

Display the track's file name next to the target point.


Display your speed next to the target point.


Display your vertical speed (VSI) next to the target point.


Display the distance from the start next to the target point.


Display your altitude next to the target point.

Having them display next to the model required too much processing power causing display problems, so we went for a happy compromise and had them appear at the start of each segment.

The units are as selected in the units drop-down selection kph, mph, knots etc.

Hide track when running.

Some users like to Control if the track remains displayed while the replay is running., some don't. This provides the flexibility of choice.

This shows the track hidden

Here, the track is not hidden:

Point information display

You can right-mouse-click on a dot to display the details about that point.

The date(local) has been calculated from the timestamp on your track file which is recorded in UTC (old GMT) and converted to a local time based on a rough calculation of your time zone according to the longitude of the first point on the track. If the calculated time zone is incorrect, you can change it here.

The Altitude is reported in your currently selected Units and the latitude and longitude are displayed

Track Details displays

You can discover detailed analysis of your track by hovering your mouse over the File details or Point details panels.

File details

This display is populated once you have selected a track file and it has been analysed by StarTraX.

The name of the file you have loaded appears under the  File heading after we strip off the trailing file type (.gpx, .igc).

Track: is displayed when multi-tracking, and provides a reference to the point letters on the GE screen.

Theme: is the Theme deduced from the track file.

Start time: is the time and date of the first point in the track

File time: using the File date (UTC)

Local time: the local time after applying the time zone.

Duration: the elapsed time of the track in days, hours and minutes

Distance: The total distance covered in the track. This is calculated by summing the individual distance between each pair of points. The distance of an orbiting gliding track will include the distance in the orbiting.

Mode: Aerial or Surface. StarTraX analyses your track and deduces if the activity you were engaged in was Aerial (flying, gliding, paragliding etc) or Surface(driving, skiing, sailing etc), by comparing your GPS reported altitude with the ground altitude and determining if more than 20% of the points were more than 500 metres above ground.

When in Aerial mode, it displays the track at the altitudes recorded by the GPS; when in Surface mode, it displays the track on the ground irrespective of the altitude recorded by the GPS.

Point details

This section reports information regarding the current segment of the track. In this context, the segment is the short path between the previous and the next point recorded by your GPS. These points may be only seconds apart, but in each segment StarTraX calculates, uses and display the following information:

Point: The point number of the first point of the current segment.

Date(local): The date and time in the local time zone.

Altitude: The altitude of the point. If it is a surface track, then this will be the ground altitude at the point.

Location: reported in degrees, minutes and 2 decimals of a minute.

TILT: The angle of the segment from the horizontal in degrees above the horizontal.

HEADING: is the direction of travel in degrees true (not magnetic)

WIND: If this is an orbiting glider track, the currently detected wind speed and direction.

SPEED: Your actual speed along this segment reported in your chosen units of measurement

VSI: Vertical speed. It is useful when animating flight data glider pilots and paragliders should enjoy this. When in Aerial mode, it is calculated from the GPS altitude, otherwise it's calculated from Google Earth's altitude.

This is an option with limited application but has been included as a user option. Select to Turn on Google Earth's "Time slider" control.

This is a useful facility if you want to visualize part of a track that goes through the same area a number of times - for example performing laps around a track, or travelling through the same area over a couple of days.

When it initially opens, the beginning and end "handles" are closed at the start of the replay:

To reveal the portion of the track you're interested in, you have to "grab" the "handles" with your mouse and move them to cover the time period of the track that you're interested in:

When you check the time slider, your track is re-drawn in Google Earth with each point's time stamp attached to the points.

Gliding features

StarTraX has been adopted by a significant number of enthusiasts of un-powered flight hang-gliding, paragliding and gliding and they have triggered the development of a number of features specific to their sport.

Colour the track by: Speed or VSI

The  control allows you to Control the colouring of the track lines. You can Colour the track by speed. (default) or Colour the track by VSI.

When the VSI option is selected, the color legend reports VSI in the appropriate units. The colors are automatically generated and the and break points are calculated from the data in your track file.

You can choose your own colors and break points by selecting buttons on the "Manual" row. This activates the "color Picker edit" button

Track Color Picker

This is a fairly intuitive control from which you can choose the colors and break points for Speed and VSI track coloring.

the values and colors are saved (in "Cookies") so will apply to all your tracks and will be available for subsequent StarTraX sessions (run from the same computer and browser).

Wind speed and direction when gliding

This feature only works for glider, paraglider and hang-glider tracks as it depends on orbiting tracks to determine the wind speed and direction.

PLEASE NOTE. The use of this feature uses considerable computing power during the loading of your track file, and this can result in increasing the time taken to load the track data.

It analyses the way your GPS speed varies as your heading changes through a series of orbiting turns. If you maintain a constant airspeed, then, when you head upwind your GPS speed will be lower than when you head downwind.

This can be seen from a sample thermalling track:

Here we have a portion of the track of a paraglider orbiting in a thermal. With the "Calc Wind" option enabled the wind speed and direction has been calculated and displayed in Google Earth.

The wind arrows indicate the wind direction by their orientation, wind speed by their thickness and the confidence by their opacity.

Show wind

You can de-clutter the display by turning off the display of the wind arrows to by un-checking the "Show Wind" checkbox on the Settings page.

StarTraX looks for portions of the track that display orbiting behaviour and uses the variation in the track's speed as it changes direction to mathematically deduce the wind speed and direction.

It makes the fundamental assumption that you have maintained a constant airspeed during the manoeuvre which of course is impossible in practice, but works pretty well on average.

The resulting speed and direction are displayed in the compass rose using colors and text to indicate the wind strength and a graphic to indicate the direction.

The graphic is a line drawing of Aeolus the wind god, blowing in the direction of the wind.

In this example the wind is from the North East, towards SW

The coloring indicates the wind speed, using a similar palette as for track speed, using the following colors and text to indicate the speed. We used the traditional Beaufort scale ( to classify the wind speeds, and made the assumption that no-one would be gliding in winds over force 5:



Bft force no.






< 1

< 1




1.1 5.5





5.6 11





12 19









5 and above

29 +

16 +

The actual values of wind speed and direction are displayed in the track display as shown. The wind direction is calculated to the nearest 1/16th of the compass or 22 1/2 degrees:

working clockwise from North, the compass points are abbreviated as follows:


The caption WIND S at 6 kph indicates the wind speed and direction deduced from the track details.

conf.: Low, Med or High indicates the confidence level of the reported value, and indicates the accuracy to which StarTraX has determined the wind speed.

The confidence level is affected by a number of factors, but mainly by the accuracy with which the pilot maintains a constant airspeed.

If it is uanble to deduce the wind, it displays Not available

To accommodate the reality of wind conditions at different altitude levels, we re-calculate the wind for every 1000 ft of vertical altitude. So, if you entered the thermal at, say, 5253 and exited at say, 8312 then we'll calculate the wind at the four levels: from 5253 up to 6253, 6253 up to 7253, 7253 up to 8253 and 8253 up to 8312.


Airspeed cannot be directly determined from a GPS track; all the GPS provides is the speed over the ground, however, now that we can derive an approximate wind speed and direction from an orbiting gliding path, it's "only a matter of" vector algebra to apply the wind vector to the GPS track vector to calculate the airspeed.

So, now, when the "Calc wind" option is selected, we calculate the airspeed of the track using the current calculated wind vector. As discussed above, this wind vector is only be calculated during the orbiting phase of the flight, but we apply the last known wind vector to the non-orbiting flight, until the start of the next orbiting phase. Obviously the greater the distance from the orbiting phase, the less reliable will be the result, but hey, it's better than nothing. When used wisely it may provide you with some useful analysis of your flying skills.

The airspeed is displayed in two places:

The info display window shows it

Airspeed is now also displayed in the Profile window.

The wind speed confidence can be visualized as the degree to which the application of airspeed smooths the GPS speed.

Clouds over thermals

Clouds can be generated above orbiting glider tracks. As a visual clue to the size and location of thermals, we've positioned a white, semi-transparent cloud at the top of each thermal, whose height is proportional to the strength of the thermal.

In this screen shot below, you can see a towering Cu in the foreground, indicating a significant height gain (in this case nearly 4,000 ft), and some smaller ones in the distance.

It's semi-transparent so as to not be too intrusive. The thermal strength is measured simply as the value of the height gained in the thermal (not the rate of climb, which could be a thought for the future).

They are only generated for gliding, paragliding or hang-gliding tracks.

You can toggle the visibility of the clouds from the Show Clouds check box on the Settings Menu.

This check box is displayed when StarTraX detects that your track is a thermalling gliding track, i.e. an aerial track with lots of orbiting. In this case a Cumulus cloud is generated at the top of each detected thermal.

The strength of the thermal is reflected in height of the cloud.

This check box allows you to toggle the visibility on or off.

IGC Altitude source

Control which altitude is used in IGC files with barometric and GPS altitudes. The IGC format, widely used by pilots of gliders, paragliders, hang gliders etc, allows for the altitude determined by the GPS ("GPS altitude") and the altitude recorded by the barometric altimeter ("pressure altitude") to be recorded against each point. These two readings are always different for a number of perfectly valid reasons that we won't go into here. As StarTraX started out to be a GPS track animation program and it can only display a track with one altitude, we originally took the decision to ignore the pressure altitude and to rely on the GPS altitude when animating these tracks.

However we have gone back to providing you with the option of loading either track once you have selected a file that contains both the pressure altitude track "PRESALTTRK" and GPS altitude track "GNSSALTTRK". (These names were dreamt up by other folks, so don't shoot the messenger.)

You can choose to suppress this display by choosing your preferred altitude source from the Settings menu.

If you're not loading IGC files, or if your IGC files only have one altitude, then this control has no effect on the way they're handled.

If they do have both sources, then you have three options:

Ask: Prompt for a decision at run-time. StarTraX will present you with the track selector every time you load a file with both types of altitude

it will prompt you with Please note: IGC files may contain both barometric altitude from the altimeter (PRESALTTRK) and GPS altitude (GNSSALTTRK). Set your preferences in Menu->Settings->IGC Alt source

GPS Alt.: Use the GPS altitude.

Baro Alt.: Use the barometric altitude.

Route and turn points (IGC files)

If your IGC file contains your route and turn points, then StarTraX will display them as additional "Scenery".

This feature has been developed from IGC gliding files downloaded from the OLC and bgaladder sites.

If you have GPX files with these elements then you should get the same result.

Different models when loading multiple paragliding tracks

If you are multi-tracking paraglider tracks, StarTraX will assign a different model to each of the first five track from the list of paraglider models in the list. For more than five tracks, the 6th and subsequent track just get the default first model.

I know it's a bit biased towards paragliders, but it's just one of those quirky by-products of the development process.

Flight Tracking


Flight Tracker allows you to observe and follow, in real time, the tracks of mainly commercial aircraft as they take off, cruise and land around the world. The real-time aircraft flight data has been found to be available to application developers, via an undocumented facility, from the FlightRadar24 web site.

This experimental feature has been published in StarTraX on the understanding that the flight data belongs to FlightRadar24 and its performance is not guaranteed.

The feature is activated from the settings page. Transitioning between Flight Tracking and normal GPS tracking contains some un-resolved technical challenges, so you are recommended to restart StarTraX after entering or leaving Flight Tracking.

Operating overview

Initiate Flight Tracker from the Settings menu and select a region of interest.

Use the Google Earth tools to navigate to your area of interest

Wait for aircraft icons to turn from orange to yellow (while the track data is being retrieved)

Click on an aircraft to get its details displayed and its track drawn in the Google Maps window.

Click on the "follow this flight" link to follow the flight

Use the familiar StarTraX controls to enjoy the flight

There is a lot more to this than meets the eye, and we recommend you experiment with it to give it a try. Only a handfull of aircraft have been modelled to date, un-modelled aircraft appear as boring grey outlines. We're working on it. Wouldn't it be fun to have each carrier's aircraft showing in their house livery? Possible but lots of work.

Usability Features

This section describes a collection of features that simplify the use of StarTraX

Settings retained

There is an almost bewildering array of buttons and check-boxes available to you to customize your track replay choices. Imagine having to re-select them each time you started StarTraX? To save you that inconvenience, we assume that you will normally like to retain your settings from one session to another, so the settings marked with an asterisk: will be retained from one session to the next. We get your browser to store them as "cookies". You can reset to initial settings by deleting the cookies from your browser.

Tool tips

If you hover your mouse over any button or control in StarTraX, after about 1/2 a second a panel (called a Tool Tip) will open with some additional information about how to use the control.

Computer monitor size recognition

Different PC's have different monitor sizes with associated screen resolution. To provide as much detail as possible in the Google Earth frame, StarTraX adjusts the size of the Google Earth frame to fill the monitor.

So, on a standard 1024 x 768 monitor you get

On a monitor with 1280 x 1024 resolution you get the same sized left hand panel, but more space for the GE frame

Whilst at 1920 x 1280 you get even more space for Google Earth.


StarTraX is a project that has been developed independently from Google Earth, although it is totally dependent on the amazing functionality that is Google Earth.

We at have developed an application as a speculative project to display four dimensional (latitude, longitude, altitude and time) GPS tracks in on a 2-dimensional computer screen.

On the way, we visited

Bugs and Help

We have done our best to deliver a reliable product, but as with so many things, we are only human and are therefore fallible. Please report any errors, bugs or oversights with an email to Please be sure to include the version information and as much detail as you can.

You can also email us if you have any questions or suggestions for improvement to the program (or its documentation).

Program structure

We are occasionally asked about the development and structure of the program, so here is some information.

Development environment

The original development environment was Windows XP, Microsoft Visual Studio 2005 , .NET 2.0 and Visual Basic. In March 2011 we have upgraded our development environment to Microsoft Windows 7, Visual Studio 2010 and Visual Basic .NET 4.0.

In December 2011, to extend accessability to the Apple Mac. community, we took the decision to re-develop entirely for the web, so re-engineered the entire application to HTML, javascript, PHP and Java. We are hopeful that in the not too distant future Google will extend its amazing Google Earth plugin to browsers on additional platforms such Linux, Android and Apple tablets and even smart phones. In that event we are confident that the web standards that we have adopted will enable StarTraX to run on these platforms.

High-level description.

Load a GPS track:

Reads the selected GPS track from your track file (gpx, plt, nmea or limited kml) into an array of track point objects, one object per point

Does the polar transformation trigonometry to calculate and record the speed and direction of travel in each segment between each pair of points.

Generates a KML representation of the track and displays it in GE (using parseKml).

Start the animation.

When you start the animation, it calculates the expected (real-time) arrival time at each point and starts a timer with an interval that results of around 20 frames per second

Process the timer event

At every timer event, it does the trigonometry to calculate the target point's position (lat, long, alt) based on the speed and direction of the current segment based on the actual time elapsed since the last timer event.

Positions the target point model at this new point in GE.

Calculates the camera's position (lat, long, alt, heading, tilt) using the currently active camera parameters (range, heading, tilt) relative to the target point and moves the camera to the new co-ordinates.

Bells and whistles

There are obviously many more features to the program (it runs to around 25,000 lines of code) that have not been described in this high level description. We have put a lot of time and effort into developing and refining the maths to provide a smooth and convincing animation that will remain "under wraps" for the moment

Specific Requirements

Release history

Incremental releases

releases will be recorded here in reverse chronolical order. Follow the links to read the details.

November 5 2013NEW Added export to Google Earth
November 5 2013FIX "Wind display fails when due South".
November 5 2013FIX "Using old documentation on help key".
July 11 2013NEW Revived and enhanced the Wind features Wind features that were sidelined in the migration to the Web version. They are now back bigger and better, thanks to Greg Hamerton's input, with the addition of wind arrows and calculated airspeed.
June 14 2013NEW Introduced the Track Color Picker feature.
June 6 2013MOD Overhaul of the the color coding of tracks for speed (blue: slow to red: fast) and VSI (green:up to red:down)
June 6 2013FIX "The Medium and Short smoke trails dis not show" - Fixed
April 22 2013MOD A "facelift" for StarTraX. Same functionality but a more sparkly and user-friendly interface. "3D effect" coloured buttons which now respond to your click; a brighter background; frames around the map and status panels; brighter logo.
April 18 2013ADD Vertical pan and zoom to track profile
March 18 2013NEW Track smoothing
March 18 2013NEW Flight Tracker
September 7 2012MOD Support for old version discontinued - no longer runs.
September 7 2012FIX Bug "Reports no support for Win 64". Always did, just reported incorrectly. (Plus "post-it" note on login page)
August 7 2012ADD Browser track file open.
July 31 2012ADD Google Earth "Street View".
July 31 2012ADD Scenery, Scenery tracks and scenery visibility checkBox.
July 31 2012ADDLinks from application to this documentation through the "oncontextmenu" (right-click + (Mac) control+click)
July 31 2012MOD layout of GoTo page - added highlighting and table borders
July 18 2012ADD 4th View Option:"None"

Web version July 2012

StarTraX on the web

After 12 months of hard work, we have re-written StarTraX, taking it from from the old version (Windows only, desktop application in Visual Basic) to a pure web application that now runs on the Apple Mac as well as the Windows PC.

One of the many benefits of moving to the web is that it greatly simplifies and speeds up the process of releasing fixes and enhancements. No longer will you have to download and install the new version onto your computer to get the new version as each time you access StarTraX, you will automatically get the latest version.
We will continue to use best practice procedures to ensure the quality of all changes, including rigorous change management of source code and end-to-end testing prior to release.
We will continue accompany all enhancements and fixes, however small (or embarrasing!), with a note in this section.

July 16 2012 "Java open" Release

ADD Use Java to open local files (to replace the slow file system file select with associated http POST to and from web site).
ADD "Time Slider" on points and segments.
FIX "Acft taxis above the ground" - no low flying below 120 ft.
FIX "Hesitated on start" - reset system state only at start.
MOD background of subsidiary screens is silver.
ADD commence implementing "right-click" help link to Features doco.
ADD more help info on login page.
FIX "Sometimes the target point overruns the next point and the camera continues to swing."
ADD Support for OziExplorer .plt file format

Version 3.10.3031 April 2011

This is mainly a bug fix release, although there are a three minor enhancements.

Version 3.9.3013 April 2011

Version 3.8.3010 March 2011

Version 3.8.2 February 2011

Version 3.8.1 January 2011

Version 3.7.3 December 2010

Version 3.7.2 December 2010 A major release

Four new on-screen instruments:

Speed with both analogue and digital display

Compass - showing orientation and direction of travel

Altitude - with a realistic aviation display

Vertical speed (VSI) essential for gliding activities.

For gliding tracks, it now has an analysis of wind speed and direction with on-screen indicators in the compass rose.

Some replay enhancements including the introduction of banking for all tracks, improved camera smoothing of both heading and tilt.

A third viewing option to add to "Follow" and "Observe" called "Lock" which locks the camera onto the moving target to provide a realistic replay experience.

Plus a swag of minor fixes to little bugs.

Version 3.6.6 October 2010

A minor bug-fix release to resolve some issues in multi-tracking which under some circumstances caused all tracks to start at the same time.

It also included an upgrade to the start point selection interface while multi-tracking.

Attentive users will also note that we have removed the tilt (lean forward or back, "attitude" in aviation-speak) on the models when they are flying. We realized that in the "real world", the attitude of paragliders and other aircraft isn't directly related to their angle of climb, so tilting the models based on their angle of climb/descent wasn't very realistic.

It's still there for ground-based activities like skiing, cycling and driving (in cars).

Version 3.6.3 September 2010

This was a minor bug-fix release including the removal of unused reference code to reduce the size of the installation file from 15 to 9 Mb.

It coincided with, and was tested on Google's release of GE API

Version 3.6.2 August 2010

In looking for ways to improve the realism of the replay I have to walk the tightrope between the desire to display a great deal of detail and at the same time provide a smooth animation both of which put enormous loads on the computer processor to perform immense numbers of calculations at blistering speeds. The fact that a domestic desk-top computer can come close to achieving this is a constant source of amazement and awe!

This release contains further enhanced the replay mechanism which have yielded a further major step up in replay smoothness. You can now zoom right into the cockpit of your fast moving aeroplane or hover 50 metres from your skier carving down a back run. You can follow your paragliders from a distance, or close in as they tightly circle in the thermal.

It's not perfect, I know but given the practical limitations of the processor in your desktop PC or laptop and your broadband internet connection, it's pretty good (even if I do say so myself!).

Experimenting continues with coding techniques to deliver even more realistic replays.

Some major improvements have also been made to the multi-tracking feature, providing a simpler method of loading multiple tracks by making multiple selections from the Windows File open dialog box instead of having to load each track separately. The details are explained in the User Notes installed with the program update.