Race Technology Knowledge Base | AnalysisOptions / GPSOptions

GPS options

The options available depend on the hardware you are using and the liciences that you have bought for your system.

The Race Technology data loggers log two separate “streams” of data from the GPS unit:

Standard speed and positional information, this is available from all hardware irrespective of the age
A complete data stream from the GPS unit, this includes speed and position (as above) but in addition this also includes heading, gradient as well as all the raw unprocessed GPS measurements. This information is only available on DL2 and later DL1’s (from 2008 onwards).

For many applications it doesn’t matter if you use the older “standard” mode, or the newer “raw GPS” data mode, however generally it is better to use the raw GPS data if it is available as this can potentially be more accurate and contains more channels of data. If you are unsure, then you can enable raw data and process a run, if the raw data is unavailable the software will display a warning.

If you are using “the raw GPS data” then you get some additional options:

“Use pre-processed 5Hz/10Hz data”. This is the “normal” mode where the GPS module in the data logger works out its speed and position etc, and the logger stores this information. Depending on the logger hardware, this is either at 5Hz, 10Hz, or 20Hz
“Use post-processed 20Hz data”. This is a more advanced mode that uses the raw measurements stored during logging and the PC is used to convert these into speed, position etc. The advantage of using this mode is that the data is potentially significantly more accurate and the data is available with an true update rate of 20Hz. The disadvantage is that the data takes slightly longer to process.
“Use post-processed 20Hz data with PPP”. This is the highest accuracy mode currently available and it uses the raw data from the GPS system combines with corrections downloaded from the internet to generate speed and positions. More information about this mode is available here http://www.race-technology.com/wiki/index.php/Technical/PPPMode

Note that when you use the more advanced 20Hz or 20Hz with PPP you get some additional options on certain systems.

Advanced GPS Options

Apply velocity smoothing.

This option uses the very high accuracy velocity data to reduce the noise in the positional data.

The velocity data and the positional data are calculated almost completely independently within the software so it is valid to use the positional data to aid the velocity and visa versa. Using velocity to aid positional information and reduce noise is an advanced technique that is becoming increasing popular in high end systems and has no significant disadvantages except a very small increase in computation time. It’s generally recommended to leave this option enabled.

Use advanced satellite weighting.

This option attempts to increase the reliance on the satellites with the best quality data and reduce the weighting on the remaining satellites. In practice the algorithm typically offers only a marginal improvement under typical operating conditions, and adds 25% to the data processing time. It’s generally recommended that option is left disabled.

Limit rate changes with vehicle model.

This option corrects and anomalies in the data based on the maximum possible accelerations, rate of change and velocities. The filter normally removes any obvious spike and also improves the noise at low speeds. The filter doesn’t constrain the dynamics of the system and is very fast to operate. For all land based vehicles it’s recommended that this option is left enabled.

Force GPS reprocessing when data is reprocessed.

This option is normally only required for specialist and development applications – typically this option if left disabled.