[Captivate Android Development] Da_G:
Just got back from going on a ride trying to do simultaneous NMEA captures from both devices.

What a nightmare that turned out to be :) I only found one app that will save NMEA data free on

the market (Aspara), and it's got some horrible programming for the NMEA log buffer.. looks

like it's doing a copy/dealloc/realloc each NMEA packet to grow the buffer or something, after

a short period of time the program was entirely non responsive and I lost all that NMEA data.

:X

Also the Bluetooth GPS providers send location data directly to the LocationProvider as a Mock

Location (lat, long, alt), pulled from the NMEA strings rather than sending the NMEA strings

irectly. That means whatever Bluetooth GPS Provider app i'm using would need to support it's

own saving of the NMEA logs to SD (none of the ones I tried do)

So i'll definitely have to travel with the laptop to collect that from the BT GPS. I'll need to

find a better app to save raw NMEA data from the captivate's GPS as the Aspara app definitely

does not work well for that purpose. It does however work fine as long as you don't allow the

buffer to grow to a point that your phone implodes, and save the NMEA log to SD. I'll see if I

can get some shorter tracks to work with that. Might be easier to write my own app to capture

the raw data from the exposed char device :P

So, lacking the raw data for this go-round to anaylze I decided to use what I had to work with,

my eyeballs! Stuck the BT GPS on the dash and held the Captivate right next to it, monitored

the BT GPS SV SNR levels with the BT GPS app on another cappyand used GPS Test to monitor the

same levels on the first cappy. Here's what I observed after about 15 minutes of staring

intently while on the move:

Signal levels are quite similar, with the BT338 edging the captivate out across the board. The

difference isn't incredible however, the cappy is still getting more than enough signal to

perform properly. There's an average difference of perhaps 3dB. Fluctuating between 0 dB

difference and 6dB difference. On the dB scale that is a significant amount however, for each

3dB you are doubling the signal. So at a 6dB difference the BT338 is receiving 4x the amount of

signal that the captivate is. These signal levels fluctuate fast enough that judging it with

the eye isn't a good measure however, really I need to collect raw NMEA data from both devices

side by side on a trip with varying circumstances and average it out to get a good idea of the

signal differences. But my eyeball tells me "negligable"

Interestingly, the small bit of google My Tracks I did today had the Cappy GPS spot on. No

changes from when I ran the same test yesterday, except that I was tinkering with lbstestmode.

I noted previously that lbstestmode initializes the GPS with a testmode = 1 flag set, that

isn't set during normal operation. This flag may in fact alter some behavior on the GPS in a

desirable way! Need more data.

I'll go outside in clear sky view with the laptop, BT GPS, and 2 cappies later today, and see

if I can collect some NMEA data to look at. I did observe the NMEA output from the captivate is

non-standard (there are date and timestamps present in the output before the actual $GP****

NMEA data, and there are a few $P**** proprietary GPS strings that show data such as fixed or

not, and some record of Tx/Rx counts.)

So to sum this post up, interesting results, NEED MOAR DATA (especially on tracking with

test mode initialized to true)

[Edit: I'm going to start a new thread shortly just for holding raw GPS data (no anecdotal observations) and instructions how to collect that data. That way we can get a more objective look on whats happening rather than the piles of anecdotal data floating around.]