Anyone experience GPS accuracy issues with Harry's Laptimer?

[Kong Sheng Han]

I'm not using any accessories with HLT, and I experience accuracy issues with the GPS. If anyone can offer possible solutions, that'd be great.

Back in January, when I first used HLT, I had the phone in portrait orientation. Track map looked okay and only had a few discrepancies (see photos)

At my last two events, I switched to landscape, and the map has been way off. I think only one lap looked good out of a hundred or so. Adding in an OBD adapter seemed to make things worse.

I'm not sure if changing the orientation of my phone is a contributory cause; just stating what change I made. I've been thinking about simply dumping HLT and switching to AIM Solo DL, since there isn't really a good stopgap solution. I plan to get an AIM Solo somewhat soon anyways (~4-6 months) for more in-depth analysis that HLT won't allow.

Edit: I also upgraded from rookie to petrolhead edition between first and second event.


Notice the discrepancies in the track map


No track map because it was way off and is useless

[okusa]

You need an external GPS device. Otherwise, you are relying on the phone's internal one which is not powerful enough to provide reliable results with HLT. You should get one even if you plan on buying an AIM unit since it's nice instant feedback and the overlay is simple without having to hook up your computer.

[Kong Sheng Han]

Originally Posted by okusa

You need an external GPS device. Otherwise, you are relying on the phone's internal one which is not powerful enough to provide reliable results with HLT. You should get one even if you plan on buying an AIM unit since it's nice instant feedback and the overlay is simple without having to hook up your computer.

So you're suggesting that once I get the Solo DL, I use both AIM and HLT. HLT for trackside analysis, and AIM for in-depth analysis? If so, that sounds like a good idea..if I have room on my windshield to put both phone mount and AIM mount.

Would this 5 Hz GPS, that our fellow forum member is selling, be sufficient? The 160 is 10Hz, but I'm not sure if the difference would be that big of a deal.
http://www.m3post.com/forums/showthread.php?t=1273995

I wonder what my lap times would've been if I'd used an external GPS.

[redpriest]

Honestly, even without external GPS when I've kept my phone with HLT running in my storage compartment in the center console, it was good enough to get lap times close enough to what AIM Solo DL was reporting, within a few milliseconds. It's just not good enough in terms of seeing what your lines are like.

[Sleeper519]

I still enjoy using Harry's because its cheap and it works. Obviously the Traqmates and the newer AIM Solo stuff, etc will give you lots and lots of data if that's what you want. I just needed laptimes with video overlays, sector splits, and lap-to-lap comparisons. The 1hz on the iphone was just fair but stepping up to even 5 hz improved the accuracy tons.
At several VIR events I used a transponder along side of HLT and plotted the times. they were good out to a few thousanths of each other and occasionally differed by hundredths--never by tenths. The small differences were all spread evenly hi/low, meaning one wasn't consistently higher or lower than the other, and the average time over a session was pretty damn even. For our (amateur) purposes, I don't feel that bumping up to 10 hz will give you any more "usable" accuracy unless your racing.
I went the HLT route because I tried not to get sucked up in the quest for ever higher electronics (hell, all this track stuff is crack anyway). Figured I just save money for fresh rubber and plump brake pads>

[beats]

You can pick up a Dual XGPS150A for pretty cheap now that the newer model is out. They run at 5hz and work great. I just use painters tape to tape it to my dash for the day...

http://gps.dualav.com/explore-by-product/xgps150a/

[Nugget]

Originally Posted by Kong Sheng Han

So you're suggesting that once I get the Solo DL, I use both AIM and HLT. HLT for trackside analysis, and AIM for in-depth analysis? If so, that sounds like a good idea..if I have room on my windshield to put both phone mount and AIM mount.

Would this 5 Hz GPS, that our fellow forum member is selling, be sufficient? The 160 is 10Hz, but I'm not sure if the difference would be that big of a deal.
http://www.m3post.com/forums/showthread.php?t=1273995

I wonder what my lap times would've been if I'd used an external GPS.

Even at 5hz it's is 5 times faster than the iphone GPS.
I have used that one for years now and Harry's is usually accurate to a hundredth of a second compared to official transponder timing.
With just the iphone it would sometimes be nearly a second off.

[okusa]

Originally Posted by Kong Sheng Han

So you're suggesting that once I get the Solo DL, I use both AIM and HLT. HLT for trackside analysis, and AIM for in-depth analysis? If so, that sounds like a good idea..if I have room on my windshield to put both phone mount and AIM mount.

Would this 5 Hz GPS, that our fellow forum member is selling, be sufficient? The 160 is 10Hz, but I'm not sure if the difference would be that big of a deal.
http://www.m3post.com/forums/showthread.php?t=1273995

I wonder what my lap times would've been if I'd used an external GPS.

Exactly. Sometimes I'm just too lazy to overlay the gopro and AIM data, so it's nice to have HLT too.

That's the same 5 Hz unit I use and it's very accurate. Typically within .001 of my AIM unit.

And there's plenty of room on the dash. You just have to position everything well.

[Kong Sheng Han]

What about the track map that shows up on HLT, does it look perfect, have some discprepancies, or look like a clusterfuck? <– This is the big question I'll need an answer to before I decide to spend money on an external GPS.

Originally Posted by Nugget

Even at 5hz it's is 5 times faster than the iphone GPS.
I have used that one for years now and Harry's is usually accurate to a hundredth of a second compared to official transponder timing.
With just the iphone it would sometimes be nearly a second off.

So you're telling me that I'm closer to the sub-2:00 mark at TWS than I previously thought. Fuchyeah!

Originally Posted by okusa

Exactly. Sometimes I'm just too lazy to overlay the gopro and AIM data, so it's nice to have HLT too.

That's the same 5 Hz unit I use and it's very accurate. Typically within .001 of my AIM unit.

And there's plenty of room on the dash. You just have to position everything well.

I use Sony camera and overlay using DashWare because my 16GB iPhone (yes, wtf) doesn't have enough storage.

I was joking about space. The two devices can go on either side of the cluster hump thing, whatever the hell it's called.

[Sapper_M3]

I have the Dual XGPS150, and it's worked great for me.

With that said, I often run HLT without the external GPS for endurance racing (because I've been too lazy to hardwire the external), and the times it provides are always within a tenth of my transponder.

I mainly keep HLT up for seeing section splits when I'm trying out different things on track.

[bigjae1976]

Among the tracks in TX, HLT data is sometimes off the most at TWS. The other tracks have fewer problems. My experience is it works better on cloudy/overcast days.

I'm getting pretty good data here...

Other times it gets weird...

[Nugget]

Originally Posted by Kong Sheng Han

What about the track map that shows up on HLT, does it look perfect, have some discprepancies, or look like a clusterfuck? <– This is the big question I'll need an answer to before I decide to spend money on an external GPS.

So you're telling me that I'm closer to the sub-2:00 mark at TWS than I previously thought. Fuchyeah!

I use Sony camera and overlay using DashWare because my 16GB iPhone (yes, wtf) doesn't have enough storage.

I was joking about space. The two devices can go on either side of the cluster hump thing, whatever the hell it's called.

Track map will be closer with the external gps.

[tdott]

A 5Hz GPS is a huge improvement, paired with an OBD reader I think HLT is great. I never got around to trying PIP with my GoPro but that should make videos even better.

[Kong Sheng Han]

Originally Posted by Sapper_M3

I have the Dual XGPS150, and it's worked great for me.

With that said, I often run HLT without the external GPS for endurance racing (because I've been too lazy to hardwire the external), and the times it provides are always within a tenth of my transponder.

I mainly keep HLT up for seeing section splits when I'm trying out different things on track.

I wish more splits could be added to preset tracks. Would make analysis a bit easier.

Originally Posted by bigjae1976

Among the tracks in TX, HLT data is sometimes off the most at TWS. The other tracks have fewer problems. My experience is it works better on cloudy/overcast days.

I'm getting pretty good data here...

Other times it gets weird...

Mine is way off in both cloudy and sunny weather. Must be the fact that TWS is in bumfuck College Station (I'm a UT student ).

Are you going to be at COTA this weekend?

Originally Posted by Nugget

Track map will be closer with the external gps.

Okay, done. Buying GPS.

Originally Posted by tdott

A 5Hz GPS is a huge improvement, paired with an OBD reader I think HLT is great. I never got around to trying PIP with my GoPro but that should make videos even better.

That E46 sounds awesome!
I should be able to get PIP working once I get a 64GB iPhone in the fall.

[silvergray545]

Originally Posted by tdott

A 5Hz GPS is a huge improvement, paired with an OBD reader I think HLT is great. I never got around to trying PIP with my GoPro but that should make videos even better.

What OBD reader are you using?

[dparm]

Think about how much ground you are covering per second on the track. At 80mph, you are covering almost 120 feet per second. If the phone can only update your position once per second (1Hz), that basically means 120 feet per polling interval...a huge margin.

If the external units can do 5Hz, meaning 5 positions per second, that 120 feet per polling interval is now dropped to 24 (120/5). That's a huge difference. 10Hz would be 12 feet, and so on.

If you wanted to visualize this, use Google Earth and measure a 120 foot diameter circle from any given point on the track.

[okusa]

Originally Posted by silvergray545

What OBD reader are you using?

If you go to the HLT website they list the compatible devices: http://www.gps-laptimer.de/compatibility/ios

[silvergray545]

Originally Posted by okusa

If you go to the HLT website they list the compatible devices: http://www.gps-laptimer.de/compatibility/ios

Thanks!

[tdott]

Originally Posted by silvergray545

What OBD reader are you using?

I'm using the GoPoint BT1 iOS Bluetooth version,had it since it first came out.

I wonder if the Carly adapter would work with HLT, if I was to do it again I would get that one now, that way you can use the same device for two purposes.

[beats]

op, here's a gps for sale.
http://www.m3post.com/forums/showthread.php?t=1270223

[beats]

op, here's a gps for sale.
http://www.m3post.com/forums/showthread.php?t=1270223

[Kong Sheng Han]

Originally Posted by skru_fase

op, here's a gps for sale.
http://www.m3post.com/forums/showthread.php?t=1270223

Thanks. I've already PM'd the seller and am awaiting response. Also looks like I have competition from another potential buyer. :/