Thursday, February 23, 2006

Tracky: Measure your G-Force

Another product that would benefit from a longer running time during its trial period is Tracky, a promising new entry to the PocketPC market of GPS applications. You can use Tracky's trial version for only five minutes at a time.

Tracky, besides its catchy name offers some features not found in any other package: it calculates the G-Force that might be hitting you and can present information graphically by combining up to three measurements in a single screen.

The trial includes features only available in its Pro version: Trackalyser, the combined graph mentioned above and the Dashboard where you can visualize besides lat/long your current G-Force and bearing.

The application is visually appealing and you will need to get used to its particular way to get things done. There is no help file in the current 1.2 version so be sure to take a look at the Feature tab in the website and scroll down to the detailed descriptions of each one.

POI's & Tracks

To begin with Tracky displays a screen with a grid where each block corresponds to 100 square meters. After selecting the COM port and rate of your GPS card (Config | GPS...), you can start tracking your way by selecting Track | Record. Make sure also to select View | Follow Current Position.

Things start to get more challenging when you try to use Tracky to calibrate the map image you have loaded. Instead of taking two points to calibrate a map either in the PDA or from an application running on a PC, Tracky requires that you first record a track or save a POI. You can also see tracks by putting them in the data directory of the program and restarting it.

To use a map, drop the image you want to calibrate to /Program Files/Tracky/data and restart the program. Now when when you choose Map | Select... it will present a list of available image files in that directory. Pick the one you want and the full view of the map will be displayed. Before the maps can be zoomed in, you need to calibrate it. So if you have an image that it too big, you probably won't be able see anything with the full map image. If you have a small enough map, you can move the grid around to adjust it to the corresponding location in the map. After that you can adjust the zoom level you want by dragging the ball at the top of the screen to the right for example. This will zoom into the image.

You can make measurements by tapping at any point in a map after you first set a mark on it. (Map | Calibrate, first tap, x marked on map, next tap gives you the distance from original x). You can drag the map by tapping and holding to a point. During the five minutes of usage with the trial version no tracks or POI's will be stored. But it will save the zoom level and marks you made previously.


If you are wondering how exactly Tracky can track G-Force here is a short but practical description from a MIT website:

"g"-forces are really a measure of acceleration, which is the rate of change of velocity of an object. If a car accelerates from zero to sixty miles/hour in 6 seconds, it has an acceleration of 4.3 meters per second per second. That is, every second, its speed is 4.3 meters per second greater.

To convert this into "g-force", we compare this acceleration to the acceleration produced by gravity, which is 9.8 meters per second per second. The car is accelerating at about 0.4 times gravity, or 0.4 G's.

Calibrating maps

Because the trial won't allow anything to be saved I decided to try a more direct approach. You can import a map image with its corresponding calibration data recorded in a .txt file in the following format described under Features | Map | Import/Export in the website:

width = 1024
height = 768
lat = 51.73585100
lon = 5.28362500
widthM = 758.610657

Where widthM is the distance in meters covered by the map image. According to data from this post, at 38 degrees a minute corresponds to 6,608 feet. Here is a calculator that you can use to convert feet to meters.

To obtain the width and height in pixels you can use Paint and check under Image | Image Attributes for its values. If you are exporting a map from Topo! for example, you can mark the exported area in such a way that it will match a specific latitude/longitude. The values provided with the .txt file need to match the top left corner of your image. Remember to convert the degrees, minutes and seconds into degrees.

Notice that your map image will have to be pointing North. But I probably did something wrong along the way because my current position was quite far to the left from the map image itself. But at that point the map was "calibrated" meaning that I could zoom into it and recalibrate it to match my current position.

Select Map | Calibrate one more time and move the grid to match the little guy showing your position. You can keep doing it while a track is being recorded so you can adjust it to match the map image.


Tracky is a nice entry to the dedicated GPS applications market for PocketPC applications, but it forces you into a new way of accomplishing things which might take a while to get used to it so I believe that it would benefit from a more standard approach and simpler way for things like performing map calibrations. It should also consider supporting standard file formats for logging tracks and POI's. Currently on its version 1.2, Tracky Lite sells at Handago for US$24 and Track Pro for US$36.

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