gps-wizard
Filtering - WIP
Introduction
There are a number of ways that the quality of GPS data can be assessed.
The current rules of GP3S state the following:
A valid run has no spikes and no strange accelerations or decelerations. If a spike occurs at the end of a run (because of a crash) the spike may be deleted and the run can count as a valid run. When there are strange decelerations a run can also be discarded.
For Verified devices in the GPS analysis software the following settings are necessary:
- max. Accel. [5 m/s²]
- max. HDoP (5)
- min. Sats (5)
Notes
- Max. acceleration was originally 3 m/s² but was updated to 5 m/s² in the GP3S rules v9.0 A2 on 1 Jan 2012.
- GPSResults and GPS Speedreader actually implement 4 m/s² for 1 Hz devices.
- The rules on GP3S were only updated to show 5 m/s² in late 2015 / early 2016.
- Distance sailed has a minimum speed requirement of 5 knots since the GP3S rules v9.1 A2 on 12 Dec 2016.
General
| GPSResults | GPS Speedreader | GpsarPro | |
|---|---|---|---|
| min. speed 1 | 5 knots | 0.6 knots | 5 knots - nm only |
| max. HDOP | 5.0 | n/a | 5.0 |
| min. satellites | 5 | 5 | 5 |
1 - The minimum speed filter is applied to the distance sailed during a session. It was added to the GP3S rules v9.1 A2 on 12 Dec 2016.
The minimum speed filter is slightly controversial as can be see in the related thread on GP3S.
Maximum Speed Speed Error
This is derived from SDOP / SDOS (Locosys GT-31, GW-52, GW-60) or sAcc (u-blox devices such as the Motion or ESP-GPS).
| GPSResults | GPS Speedreader (SiRF) | GPS Speedreader (UBX) | GpsarPro | |
|---|---|---|---|---|
| max. speed error @ 1 Hz | 2.0 knots | 2.0 knots | 1.2 knots | 2.0 knots |
| max. speed error @ 5 Hz | 4.0 knots | 4.0 knots | 1.2 knots | 2.0 knots |
| max. speed error @ 10 Hz | 4.0 knots | 4.0 knots | 1.2 knots | 2.0 knots |
Maximum Acceleration
This is derived from the change in speed between two readings. This naive calculation results in higher values for 5 Hz and 10 Hz devices.
A dedicated article will discuss the topic of acceleration in more detail.
| GPSResults | GPS Speedreader | GpsarPro | |
|---|---|---|---|
| max. acceleration @ 1 Hz | 4 m/s2 | 4 m/s2 | ? |
| max. acceleration @ 5 Hz | 7.5 m/s2 | 8 m/s2 | ? |
| max. acceleration @ 10 Hz 1 | 15 m/s2 | 16 m/s2 | ? |
1 - The max acceleration for 10 Hz devices was increased from 8 m/s2 to 10 m/s2 in GPSResults v6.173.
2 - The max acceleration for 5 Hz and 10 Hz devices was observed to be 7.5 m/s2 and 15 m/s2 in GPSResults V6.187.
Altitude Changes
A dedicated article will discuss the topic of altitude changes in more detail.
Screenshots
GPSResults
GPSResults v6.185 applies the following default filters:
GPS Speedreader
GPS Speedreader v1.4.3 applies the following default filters:
