Harry's GPS Suite Forum

Howdy everybody,
i have been trying like heck to get HLT to work without to much luck. I'm new to HLT and to data acquisition all together so please bear with me.

Equipment:
newest version of HLT.
Iphone 4.
Dual XGPS150A. strapped to wrist
OPTRIX helmet mount.

Location:
Indoor rental Kart track.
42.00 second track.
top speed around 45mph
1 POI set start/finish on the finish line

Problem:
start/stop seems to happen all over the track (if at all) for both video and data.
the last race i did is as follows
first race
lap 1 16.88 w/video
lap 2 31.66 w/video
lap 3 1:03.68 w/video
all remaining laps(8) bundled into one 9:56.26 w/ no video associated with laps but the raw video was recorded

second and third races didnt record at all but im not so sure that wasn't user error

that was the first time i was able to get the trigger to activate at all. every other time i tryed when i checked the data after the race it had the orientation message. i was able to stop that problem by changing the expert settings for landscape rotation to 10. also had set the detection corridor to narrow to try and get it to pickup correctly.

Am i missing something, i really would like to get this figured out. i have read many different posts and haven't been able to determine what i am doing wrong. i have looked at my POI in the map view and it is out in the parking lot of the building for whatever reason????

HELP!!!

Joe Prue

Hi Joe,

Please export your laps (including the bundled one) to .kml and send it to me Harry@gps.laptimer.de I will analyze and come back. I assume there is a problem with GPS accuracy. You say 'indoor' kart track, have you checked your GPS accuracy before? Usually, GPS is not good enough within building to get LT work.

- Harry

Harry, I hope that is not the case. I have exported and sent you the file. That was the first time I exported and I didn't realize you could export all, so the first two are the first two laps and then I sent all laps in the third. Hope you can get this working for me, I do competitive race league and it would be a valuable tool. I have checked the gps bars and they are in the green, is the any other values I should be checking?

Sorry, wrong email address, please use: Harry@gps-laptimer.de

Sent

Hi,

Please have a look into the snapshots attached below. That's actually what LapTimer 'sees' and needs to interpret... The blue bubble denote the area of confidence the GPS delivers. I believe the area is still too small as I can hardly recognize a track shape. I doubt it will be possible to get good enough positions within the hall as GPS receivers require a 'free view to the sky' to work effectively.

Sorry to say, but this 'in hall' driving will most probably not work with a GPS based tool.

- Harry

harry, well at least i know its not something i'm doing wrong. that being said is there anything else i can try and do to achieve some sort of results. At this point i'm already invested with both money and time. stronger GPS? Two GPS? Jailbreak? ANYTHING!!

by any chance does the direction i was facing when i set the start/finish have any affect on results?

Actually there are three GPS quality levels LapTimer faces:

• Good GPS accuracy (achieved either starting with the iPhone4's internal GPS, or any of the external GPS solutions, outside) -> allows both lap timing and reasonable data recording / plots for analysis
• Low quality GPS accuracy (typically seen for iPhone3G & 3GS, outside) -> allows lap timing, but is pretty limited on data recordings as the plots are not accurate enough
• No relevant GPS accuracy -> neither timing, nor data recording possible

My point of view is you are somewhere in between 2 and 3 - although you are equipped with a good GPS already. You may be able to get reasonable lap times sometimes, but data recording will not possible at all under this conditions... I have really no idea how to get a GPS solution working indoors... But maybe you have the opportunity to visit some outside kart tracks from time to time?

- Harry

Harry, just read the announcement for the VBOX Sport 20 Hz GPS. Would this help in my situation?
Thanks, Joe.

I had no chance to test the device on my "reference" track Nordschleife but will post once I have a valid sample to compare. In general high update rates come at the price of accuracy. The VBOX Sport should play in a different league however and I hope to see better update rates AND accuracy / lock stability.

- Harry