Harry's Lap Timer for Android: Now Available

[CSG Mike]

Originally Posted by ultra

interesting. I supoose it's good enough as a basic ballpark lap timer then, but probably not accurate enough to tell you whether X clicks on the suspension or Y adjustments to tire pressures gained you a few tenths or not.


I just picked up a Dual XGPS160 bluetooth GPS receiver to enhance the accuracy a bit. Will report back later on.

Link: http://cgi.ebay.com/ws/eBayISAPI.dll...m=151198332735

i'll try logging side by side with both the iPhone 5. running HLT Grand Prix and the Nexus 7 running HLT Rookie to see the differences as well.

Next step after that will be to try and hook up a GoPro Hero 3 Black editon and see if i can use that for overlays.

It's better with external GPS, but I don't have enough experience to say how much better. Theoretically it should be +- 0.2s with it.

[acro]

Question : is Harrys lap timer for android as good as for ios.

Does Harrys lap timer for android allow video recording and overlay of data on the phone at the same time?

Thanks

[jvincent]

Yes, the android version supports video recording and overlay of data. The overlay is a post processing function, but I believe that is the same as in iOS.

One caveat on the video/overlay function is that it can only handle a 2G file. So, if you record video for multiple laps in HD you may end up with a file greater than 2G. It's easy enough to reduce the file size before you run the overlay process, but I thought I'd point that out.

Oh, and if you are recording video your phone will get hotter than fuck and it's a very big battery drain so make sure you bring a charger with you.

[D K]

I dont know if you guys know this or not, but the new sony has a built in gps overlay (and image stabilization)

D

[ZionsWrath]

Originally Posted by D K

I dont know if you guys know this or not, but the new sony has a built in gps overlay (and image stabilization)

D

sony? sony what

[glamcem]

I tried Harry's Lap Timer when they first released the Android version but it didn't really impress me since I don't like the cell phone video quality (shaky and poor quality) ..I've been using RaceChrono and recently upgraded to the Pro version.. RaceChrono is free and with an external GPS (Qstarz BT-Q818XT) and RaceRender 3 it's pretty easy to make a video with telemetry .. External GPS is a lot better option who looks for a more accurate data sampling

[D K]

Originally Posted by ZionsWrath

sony? sony what

This guy here:

[BRZ NA]

Any one have android phone instead iPhone that can connect Harry's lap timer with gopro? I've been searching but can't find any, it's sucks when they can't do it like iphone

[TemeCal]

Originally Posted by CSG Mike

I'd give it a +- 0.75 second window (although it can be +-1), from my observations, comparing it to a Racepak and AIM unit, as well as AMB and Westhold timers.

I know you're referring to using HLT without an external timer, but your numbers seem high. I run it with an external GPS, and my experience has been extremely positive. My lap times according to HLT, are always within 1/100th of a second to the transponder SpeedVentures or Extreme Speed provides.

I always compare each lap time with the transponder printouts, and have found HLT to be surprisingly accurate. Would I prefer an AIM? Absolutely. But for the price of HLT and an external GPS, it does very well.

[CSG Mike]

Originally Posted by TemeCal

I know you're referring to using HLT without an external timer, but your numbers seem high. I run it with an external GPS, and my experience has been extremely positive. My lap times according to HLT, are always within 1/100th of a second to the transponder SpeedVentures or Extreme Speed provides.

I always compare each lap time with the transponder printouts, and have found HLT to be surprisingly accurate. Would I prefer an AIM? Absolutely. But for the price of HLT and an external GPS, it does very well.

HLT without external GPS is a 1hz unit, which gives it a +- 1S range.

Although the lap times are often close, watch the "speedometer" and you'll realize how lacking 1hz really is.

[TemeCal]

Originally Posted by CSG Mike

HLT without external GPS is a 1hz unit, which gives it a +- 1S range.

Although the lap times are often close, watch the "speedometer" and you'll realize how lacking 1hz really is.

That's the reason I purchased an external GPS. They're very cheap, and have proven to be pretty accurate for me. I only track once a month, so HLT with an external GPS does a tremendous job *for me*.

I know you guys sell the AIM, so it's easy to say "HLT just isn't accurate". I just can't justify $700 for something that may be 1/100th of a second more accurate. I realize you use it for much more than a timer. If I wanted to go deep into analyzing my laps, I'd certainly pay the $700. But, I'm at a point where I just go to the events to have fun. Nothing more. At some point, it's easy to lose the fun factor at the track. I have a feeling, that for the majority of drivers at these events, HLT is perfectly suitable and sufficient.

[HarryS]

Originally Posted by CSG Mike

HLT without external GPS is a 1hz unit, which gives it a +- 1S range.

This is not the way GPS based lap timers work. They use the last position received before, and the first position behind start / finish and interpolate the time and position the line has been crossed using "interpolation". For cars crossing a typical start / finish at around 200 km/h, this interpolation introduces a very small error. This in turn means the receiver update rate has a pretty small influence on timing accuracy, while *position accuracy* has a strong effect. Or in other words: a 1 Hz device delivering 2 meter accuracy will generate a higher timing accuracy than a 5 Hz device at 10 meter position accuracy for most cases.

High update rates are good to get a better understanding of line driven, breaking points etc, and is better in catching speed peaks. The influence on timing accuracy is small but increases for low speed vehicles (e.g. karts).

In case Harry's LapTimer delivers accuracy below 0.05 seconds mostly, this is due to bad accuracy and can be improved by choosing a better mounting position for the smartphone. The most frequent problem is when the smartphone is placed in your cloth, a glove box, or on the co-driver's seat (or in his/her hands). So please always mount your smartphone on the center of your windscreen.

I do not want to post external links in my first post. In case you want further details, please ask.

Originally Posted by CSG Mike

Although the lap times are often close, watch the "speedometer" and you'll realize how lacking 1hz really is.

This is a general limitation when watching GPS data in real time. GPS speed delivered is outdated when calculated in the sensor already. This is due to signal transmission times as well as processing time. This is typically around 1 second. In addition, a latency is introduced by the update rate (0.5 seconds in average for a 1 Hz device and e.g. 0.025 seconds for a 20 Hz GPS). Finally, low position accuracy will result in stronger smoothing of data (to receive noise), so additional latency is often a signal for bad accuracy too.

The latency in this real time scenario has no influence on recording accuracy! It is always performed on complete information somewhat in the past. You will see this when a lap timer starts a lap late and stops it late again.

I hope that helps,

Harry

[HarryS]

Originally Posted by TemeCal

I know you guys sell the AIM, so it's easy to say "HLT just isn't accurate". I just can't justify $700 for something that may be 1/100th of a second more accurate. I realize you use it for much more than a timer. If I wanted to go deep into analyzing my laps, I'd certainly pay the $700. But, I'm at a point where I just go to the events to have fun. Nothing more. At some point, it's easy to lose the fun factor at the track. I have a feeling, that for the majority of drivers at these events, HLT is perfectly suitable and sufficient.

AIMs (and any other dedicated data recording system) are not more accurate than a professional track app. Instead they suffer from hardware limitations (Google, Samsung, Apple can invest a lot more in hardware development than a small niche company can do) to provide sophisticated analytics and graphics. Smartphone apps can suffer from a consumer GPS, but can be improved using an external GPS. Today, this is mainly a question of taste and personal priorities. :-)

- Harry

[TemeCal]

@HarryS -
I'm glad you found this thread, and took the time to respond. I have always been impressed with your app. You have done a tremendous job with it.

I still highly recommend HLT to everyone I meet. Price wise, accuracy, video overlay, controlling my GoPro, etc... it's hard to beat.

Keep up the great work! We really do appreciate it.

...on a side note, I'm looking forward to your "OBD Wizard". I opened a thread on your forum, about logging our oil temps. It'll be nice to have the OBD Wizard, so we can take advantage of this.
http://www.gps-laptimer-forum.de/vie...hp?f=20&t=1364