[Captivate Android Development] azranger:
Observations on Elevation Readings

Currently using Doc's ROM JPY V6.2 CE & JM9's GPS fix (was using Da_G's) and JL3 Modem. (D/C 1007)

I have noticed on stock, Assonance v5 & 5.2, Darky 7.5 & Doc's 6.2 with either stock, JK3, JK4 or JL3 Modems that I still see the same activity on the GPS readings. The elevation radically fluxuates!! I live in Phoenix so there is not much in elevation or grade changes.

First wanted to thank Da_G for his efforts on the GPS (loved your ROM's for my Fuze - That is until it decided that it wanted to go swimming one day!:eek:).

I get much faster locks and 7+ sats now with reported acc normally at 5-10m sometimes 2m with max of 30m on JM9 fix, with Da_G 30-50m with a rare 10m fix.

Now I did 2 tests, one fixed location and the other while driving.

Conditions: 7-10 Sats and sig at 25-35 on each. Note: official elevation at my location is 1237ft, well 3 miles south of me. Not sure if I lost Sat lock, did not always pay attention. Used MS Based with 50 Accuracy, GPS Plus.

Fixed Location (sitting in my driveway with phone stationary).

1) Used LBST or GPS Test to get readings and just watched as all the values changed, LAT/LON, Speed (upto 6mph) and Elevation would change by over 200 ft.

2) Same using MyTracks on a 10 minute test, but now I have some data to look back on. My last showed my stationary phone going 6mph with an elevation change of 157 feet, grade of -1.2% to -.7% and a radius of 150ft all while the acc'y was showing from 2m to 15m. Many times would show a acc'y reading of ~2m (no blue circle) while the displayed map position was 150ft down the street.

Now looking at elevation page it showed a semi bell curve starting at 834ft and peaking at about 4 1/2 minutes into the test at 991ft then declining down to 910 feet.

Moving test (Just a short drive of 2 miles on a flat straight road).

First 9/10 mile the GPS tracked me perfect, until I had to stop at light but the elevation data shows a change from 1050ft to 1124ft. While sitting at the light the elevation went down to 897ft. Note: actual elevation is ~1237ft

Light changes, driving again and the next 8/10 mile the track keeps me around the 900ft mark +/- 10ft (there is no grade or elevation change in the road) but at about 50ft to the east of my actual position. Then the elevation jumps to ~1000ft and now my track is perfect again even at the end when I turned into the parking lot and drove around and parked.

Conclusions/Observations:

1) Well I can confirm that the indeed the GPS does, well suck.

2) If the data is correct and the elevation data is reporting changes of 200+ feet with no real change in elevation then the LAT/LON will also be off as well as the speed of travel.

3) Noticed in Lbstest that at times I maintain 8+ satloc w/strength updating but none being used.

4) GPS reports accuracy of 10m or better but actual location is 50+m away.

5) That Lbstest shows latiute labels twice instead of latitude and longitude. Maybe that's a clue to the quality of the firmware.

6) Dropped satloc while stationary w/no apps running, maybe thats due to background services running and the kernal giving them priority over the GPS causing restarts.

7) Bad attenna, but that is only 1 factor on a long list.

8) I would say settings help satloc, radio could fix a lot of things, kernel issues, firmware, daemon's and interferance on the PCB (HTC phones have a lot more RF shielding on them). Just to name the top 6 on my list.