Multi-rate data export

[arvind]

Is there a way I can export multi-rate data - i.e. I noticed that when there are multiple sensors (e.g. GPS@1Hz, Accelerometer@25Hz) the exported data is down converted to 1Hz. Is this how LapTimer handles data from multiple sources? Is there a way to log (and export) data at the maximum rate supported by each sensor? Thanks!

[Harry]

LapTimer fuses all data coming and stores it at GPS rate. So to increase the data rate stored, you need to increase the GPS rate to e.g. 10 Hz currently.

Harry

[arvind]

Thanks a lot Harry. Is there a specific method (filtering, averaging etc) used to down sample the data from the higher data rate sources?

[Harry]

Yes, GPS fixes define the point in time full fixes are stored. Full fixes are made up from the (unchanged) GPS fix, and derived OBD and acceleration fixes. For OBD fixes, LapTimer applies an interpolation between the last OBD fix ahead of the GPS fix and the first one behind. For acceleration, the max value that occurred between GPS fix time - half GPS update rate to + half GPS update rate is used.

- Harry

[gplracerx]

If you just want to log data, there's an iOS app called Sensor Data from Wavefront Labs that allows you to log accelerometer, gyro, magnetometer and GPS data, among other things, at up to the maximum rate available, 100Hz. It does no data analysis. The data are available through iTunes in a .csv format. I found it works with the Emprum Ultimate plug in GPS at 5Hz, but not other GPS accessories like the VBOX Sport or Dual XGPS160, or at least not at 20 and 10Hz respectively. There's probably something equivalent for Android.

The Sensor Monitor app lets you see data in real time but doesn't log.

[arvind]

Thanks a lot for the replies - that really helps. I am looking for a good autocross setup - along with a PC based data analysis setup. The limiting factor is gathering the accelerometer data - I think >25Hz is a minimum for autocross. So a method to allow multiple data rates from sensors - while still syncing it the GPS will be really handy. I have experimented in the past with my own hardware and interpolation routines - and of course ran into the main problems of synchronizing data and reliably detecting start/finish. I recently got HLT (on Android) and will experiment with a 10Hz GPS setup. Thanks again.

[Harry]

I have posted a number of articles on a recent integration of ASL's RaceCapture/Pro MK2. https://www.facebook.com/HarrysLapTimer ... 0609428388 The integration is finished for iOS and Android already (although the device is available with BT only currently - meaning you need to tweak iOS devices to connect) and will be part of LapTimer v19. This box is an open source project and coming with a 50 Hz GPS, OBD and 100 Hz accelerometer. I have not integrated the last one yet, but this part will follow in 19.x. I do not want to push you into a specific direction but - given you worked on your hardware already - thought this is probably a good platform for you. I have not yet checked accuracy in real life tests, but get fully synchronized GPS and OBD data at 50 Hz.

- Harry

[arvind]

Thanks a lot for the info Harry. I've been reading several other interesting posts on these forums - hope to share my findings once I have every thing running.