The refrence systems are a Navi GPS BGT-11 and a Rayming TripNav TN200
Opkg tells me I have kernel "2:2.6.24+git25+8533927964761f4e2078ccd8607b90f5acc60b93-r0" installed on the FreeRunner.
I placed all 3 GPS units on the roof of my car, spaced about 40-50 cm apart. I plugged all 3 of the into my notebook via USB. I ran two instances of gpsd (version 2.36) on my notebook to controll the BGT-11 and the TN200 and I configure the USB networking with the FreeRunner so I could talk to its gpsd (version 2.34).
Next I ran three instances of xgps so I could monitor the status of the the units. This was when I noticed the first bit of wierdness with the FreeRunner; it was constantly alternating between 2D and 3D fix. Even though it had more than 4 strong satelite signals. It actually detected and tracked more satelites than either of the refrence systems, but the refrence systems held a 3D fix for most of the testing while the FreeRunner bounced back and forth between 2D and 3D.
Then I ran three instances of gpsprof to collect 2,500 fixes and plot them. This is when I noticed the next bit of wierdness with the FreeRunner; while it took just under 2,100 seconds to collect the 2,500 points from the refrence systems, it only took the FreeRunner less then 600 seconds. Maybe that is a difference between gpsd vers 2.34 and 2.36, I really don't know.
I ran this collection 3 times, once with the SD card removed from the FreeRunner, once with it installed but idle and once with it being used heavily. This is when I noticed the third bit of wierdness with the FreeRunner; when the SD card was being used heavily, gpsd kept dying on the FreeRunner. I had to rerun the test a few times before I successfully captured the 2500 fixes.
The results for the BGT-11
| SD Card test | Run time | CEP(50%) | # of Fixes | Position | # of Altitude Fixes | Altitude |
|---|---|---|---|---|---|---|
| Idle | 2084.95 sec | 2.756134 m | 2500 | 51.044194N,114.174713W | 2489 | 1212.023467 m |
| Removed | 2083.26 sec | 3.776681 m | 2500 | 51.044216N,114.174736W | 2500 | 1212.928348 m |
| Busy | 2082.88 sec | 1.600676 m | 2500 | 51.044210N,114.174748W | 2500 | 1214.673024 m |
The results for the TN200
| SD Card test | Run time | CEP(50%) | # of Fixes | Position | # of Altitude Fixes | Altitude |
|---|---|---|---|---|---|---|
| Idle | 2082.47 sec | 2.096085 m | 2500 | 51.044191N,114.174677W | 2500 | 1213.947100 m |
| Removed | 2083.82 sec | 2.467722 m | 2500 | 51.044188N,114.174692W | 2500 | 1214.740792 m |
| Busy | 2083.52 sec | 2.267680 m | 2500 | 51.044194N,114.174690W | 2500 | 1214.795966 m |
The results for the FreeRunner
| SD Card test | Run time | CEP(50%) | # of Fixes | Position | # of Altitude Fixes | Altitude |
|---|---|---|---|---|---|---|
| Idle | 499.98 sec | 1.611909 m | 2500 | 51.044235N,114.174706W | 2000 | 1216.774200 m |
| Removed | 500.16 sec | 2.561012 m | 2500 | 51.044191N,114.174683W | 2000 | 1217.397600 m |
| Busy | 563.57 sec | 7999885 m | 2500 | ??N,??W | 1906 | 1214.926285 m |
20080802
Updated the FreeRunner today and reran the tests.
Also did a bit of digging into the wild values showing up on the FreeRunner when the SDCard is busy. It turns out that gpsd will return a value of 10,000,000,000 as the value of NaN. So if you are averaging a buch of values that should be around 51.0xxxx it doesn't take very many instances of a value of 10 billion to really screw up that average. gpsprof expected to find NaN in the altitude field, but didn't check for it in lat. or long. I modified gpsprof to throw away any sample with lat. or long. out of range.
The results for the BGT-11
| SD Card test | Run time | CEP(50%) | # of Fixes | Position | # of Altitude Fixes | Altitude |
|---|---|---|---|---|---|---|
| Idle | 2084.82 sec | 4.209351 m | 2500 | 51.04440N,114.174483W | 2496 | 1216.4960002 m |
| Removed | 2083.73 sec | 2.478665 m | 2500 | 51.044367N,114.174468W | 2500 | 1213.24324 m |
| Busy | 2088.56 sec | 5.077799 m | 2500 | 51.044423N,114.174477W | 2499 | 1215.274126 m |
The results for the TN200
| SD Card test | Run time | CEP(50%) | # of Fixes | Position | # of Altitude Fixes | Altitude |
|---|---|---|---|---|---|---|
| Idle | 2084.63 sec | 4.211493 m | 2500 | 51.044385N,114.174471W | 2500 | 1218.340160 m |
| Removed | 2084.30 sec | 4.107383 m | 2500 | 51.044372N,114.174498W | 2500 | 1213.524064 m |
| Busy | 2086.53 sec | 5.278166 m | 2500 | 51.044395N,114.174482W | 2500 | 1218.394984 m |
The results for the FreeRunner
| SD Card test | Run time | CEP(50%) | # of Fixes | Position | # of Altitude Fixes | Altitude |
|---|---|---|---|---|---|---|
| Idle | 499.86 sec | 1.468396 m | 2500 | 51.044455N,114.17446W | 2000 | 1223.977800 m |
| Removed | 500.00 sec | 1.645148 m | 2500 | 51.044393N,114.174437W | 2000 | 1220.398400 m |
| Busy | 590.45 sec | 1.288408 m | 2498 | 51.04448N,114.174460W | 1847 | 1224.044884m |
