Hi All,
I am using SportsTracker v1.82 on my E71.
The GPS itself should have an accuracy of 5-10 meters, should'nt it? But based on the recorded data, I have serious doubts about the accuracy of the altitude figures.
Any comment, experience or opinion about that?
Regards,
Sasmadar
Normally height accuracy of a GPS antenna is 2-3 times worse than the position accuracy.
Your position accuracy is depending of the antenna and the GPS you're using. Normally it's between 10-15m, which means your height accuracy would be about 20-45m.
I find that when running down normal streets with 2-3+ floors then the accuracy goes way down. The tracker seams to try and guess where I am and so jumps around a lot. Does anyone know if the GPS filtering option makes any difference?
When I am out in the open e.g. running beside a river/canal it works much better.
the accuracy of a gps depends on the number of visible satellites. when you're running down down a street you have less visibility of the sky (and of the satellites) compared to when you're running on an open field. Also when you have building next to you, you might have problems with reflections. GPS measures the distance from different satellites using signals emmited from the satellite. Some of theses signals now get reflected on the buildings before they reach you receiver. Therefore the distance the receiver thinks is your distance to the satellite actually is the distance satellite-building-you. This will cause the jumping around effect you describe.
My problem is just with the altitude figures.
With the xy coordinates everthing seems to be fine.
But concerning the hight I still believe that there is an issue either with the way of calculation or the way of putting data on the chart.
The USGS provides detailed elevation data for more than just the US (I live in Sweden). That information can used to replace the satellite altitude data after the horizontal route is mapped.
This solution works well in a sports analyzation program I'm using called TrackRunner. I export a GPX file from my NST app to the desktop software and then run an elevation correction feature with data supplied via USGS. Cleans up the data nicely and quickly.
Either through an automated or manual option, it would be great to have the ability to remove obvious GPS data samples which result in map and elevation anomalies. On a few of my routes you can see my altitude drop as far as -200m in a single spike, thereby throwing off the profile scale for the entire workout. Removing these anomalies is easy after I export in GPX or KML, but I have no way to delete the samples on the NST site.