Search found 816 matches

by gplracerx
Mon Aug 19, 2013 5:34 pm
Forum: Using LapTimer
Topic: GPS vs OBD speed calibration
Replies: 5
Views: 3681

Re: GPS vs OBD speed calibration

1% is pretty good actually. I can change the tire revs/mile in the engine computer so I can calibrate to one part in about 750 or ~0.13%. Of course I need to drive about 75 miles to check the accuracy to that level. You can eyeball at lower miles by watching when the GPS display changes compared to ...
by gplracerx
Mon Aug 19, 2013 5:19 pm
Forum: Feature Requests
Topic: Adding atomic clock and other features for road rally.
Replies: 18
Views: 11310

Re: Adding atomic clock and other features for road rally.

At 105 mph, 0.1 seconds is 15.4 feet. That's starting to push the limit for accuracy for normal GPS. At 85 mph, you're losing about 8 seconds per mile compared to 105 mph. So if you were ahead 8 seconds, you would need to slow down to 85 about 0.5 miles from the finish line. There is an average spee...
by gplracerx
Mon Aug 19, 2013 4:46 pm
Forum: Using LapTimer
Topic: GPS vs OBD speed calibration
Replies: 5
Views: 3681

Re: GPS vs OBD speed calibration

If your speedometer and odometer are run by the engine management computer, the most accurate way to determine a correction factor for OBD vs GPS wheel speed is to use the odometer. Compare GPS miles traveled vs. odometer miles traveled. The correction factor is then the GPS miles traveled divided b...
by gplracerx
Mon Aug 19, 2013 4:38 pm
Forum: Global Navigation Satellite System (GNSS) Sensors
Topic: iOS Location Services and external GPS
Replies: 4
Views: 2951

Re: iOS Location Services and external GPS

I ran an autocross this weekend with Location Services off and a Dual XGPS160 with no problem, but I wasn't using video. The HLT times were nearly identical to the official times. I had to reboot several times on Saturday, but not on Sunday. I think it helps to forget all the Bluetooth devices, not ...
by gplracerx
Thu Aug 15, 2013 3:37 pm
Forum: Feature Requests
Topic: Adding atomic clock and other features for road rally.
Replies: 18
Views: 11310

Re: Adding atomic clock and other features for road rally.

Unless there are intermediate official checkpoints, I don't see why you don't go as fast as you can so that you get near the finish line with time to spare and then slow down. I still fail to see the need for intermediate splits. All you need to know is that your average speed is greater than 105 mp...
by gplracerx
Thu Aug 15, 2013 3:35 am
Forum: Feature Requests
Topic: Adding atomic clock and other features for road rally.
Replies: 18
Views: 11310

Re: Adding atomic clock and other features for road rally.

I presume that the starting time is on the minute, so you don't really need a stopwatch. GPS Buddy would seem to be the better app. Program the start and finish points and adjust your speed to keep the ETA at the finish at the correct absolute time. In your example above it would be the starting tim...
by gplracerx
Wed Aug 14, 2013 8:38 pm
Forum: Global Navigation Satellite System (GNSS) Sensors
Topic: XGPS150 5 Hz update.
Replies: 140
Views: 63115

Re: XGPS150 5 Hz update.

" No firmware updates required for that bad boy to get it to work right?"

Not so far. It looks to me like the XGPS160 is definitely worth the extra cost.
by gplracerx
Wed Aug 14, 2013 8:03 pm
Forum: Engine Sensors
Topic: Bluetooth OBD dongle connects, but no data transmitted ...
Replies: 22
Views: 10518

Re: Bluetooth OBD dongle connects, but no data transmitted .

I suggest doing the same thing as Dual suggests for connection problems in iOS 6.1.2 and 6.1.3 to its Bluetooth GPS devices. Go into the Bluetooth page in Settings and forget all paired Bluetooth devices. Then kill all running processes and reboot. Pair the devices again and connect. http://gps.dual...
by gplracerx
Wed Aug 14, 2013 2:17 pm
Forum: Global Navigation Satellite System (GNSS) Sensors
Topic: Dual XGPS160
Replies: 217
Views: 103169

Re: Dual XGPS160

... and here is the answer (for the really brave ones ;-) ): http://www.gmat.unsw.edu.au/snap/publications/han_etal1999b.pdf - Harry That paper refers to RTK, Real Time Kinematics. The position accuracy of RTK is on the order of two centimeters because the receivers use the signal phase from each s...
by gplracerx
Wed Aug 14, 2013 2:51 am
Forum: Global Navigation Satellite System (GNSS) Sensors
Topic: Dual XGPS160
Replies: 217
Views: 103169

Re: Dual XGPS160

GLGSV, GPRMC, GPGGA, GNGSA