Some lack of accuracy?

Sep 5, 2009 at 10:10 PM
Edited Sep 5, 2009 at 10:16 PM



I suspect a little lack of accuracy (in some moments much bigger that the supposed acceptable accuracy of a regular WinMo GPS/Phone system). I mean in some moments about 200 meters of difference betwwen the real point where I was and the saved point.

Also, is another issue, that is not about an error, but about best practices: I make today for example a trip with a city bus (so this means, not very big speed, let say an average of 25-30 km/h, an average of 500 meters between consecutive stops and so on.) The trip was around 5-6 kmeters I guess. The GPSTracka it was in a KML save mode, Track mode, and with a polling of 60 seconds. After importing the KML file in Google Earth I can say that for 60 seconds there not enough points for having a smooth track on the map (unfortunatelly I don't know how to atach the kml file to this posting, for having the full trip on the map). In some momnets of time the track it have a drawing that go trough a house or even a block.

I think to use GPSTRacka for vehicle monitoring usage. So what can be a best practice for poling time but for not having a very much GSM/GPRS or 3G data usage? (It suposse that I plan to send the KML data or maybe kml file to server where to parse and display on the map).

And another one: for me is manadtory to save/send for each slice of time not only the Long/Lat info, but also the instant speed and maybe a kind of ID (I think maybe the IMEI serial or something else related to the phone) for diferentiating between diferent cars that I will track.  What is most apropriate for this: kml or gpx format?

And more offtopic: 

Anyone have an idea about how to intercept from the start/stop engine key of the car, a signal to send it via USB to the phone for acting like a click on start/stop button of the app? I think about an electrical aproach of this issue, because is also an legal issue related to serivce/warranty of the car and the act of making changes over the electrical circuit of the car. In all the cases I think that the cigare lighter is not a choice because it seems to me that for most cars, this is somehow before the start/stop key switch. I don't know, maybe the stereo can be a good example? In all the cases it must be a place in the car where we have +12 Volts only if the car engine is working...

Sep 6, 2009 at 10:56 AM

Hi net4u

That inaccuracy you see is normal, especially in urban areas.  You'll see that it works better when you're actually moving, but when you're still the points are all over the place.  The accuracy depends on the quality of the receiver in your device or phone. 


As for your smooth-route problem, you will need to bring your interval down.  If you bring the interval down, then the KML file will grow faster, so GPX is better in such a situation.  Also, please note that the GPSTracka doesn't use your data connection.  It's only logging to a file.


For the extra 'metadata' that you want, both GPX and KML can do this.  GPS has the <extensions> tag, KML has the <extendeddata> tag. They can store custom info but your reading application will need to understand them.  This is obviously not going to included in GPSTracka but you could always modify the code yourself.



Your offtopic question is intriguing though, I don't even know if it's possible.  If you have a direct stereo-USB connection and you can get your phone to have a running app that detects such a connection, you can use GPSTracka's autostart parameters to start the app up.  I have NO idea if this is possible, though.