Experiments in GPS with Raspberry Pi. See pi folder for instructions on setting up PI.
Instructions on setting up the Adafruit GPS can be found here:
https://learn.adafruit.com/downloads/pdf/adafruit-ultimate-gps-on-the-raspberry-pi.pdf
An example of accessing GPSD using the python-gps library (used as the basis for this implementation) is here:
http://www.danmandle.com/blog/getting-gpsd-to-work-with-python/
And after much searching, an explanation of the values returned by the GPS is in these two links:
http://theshipcomputer.blogspot.co.uk/2013/11/setting-up-gps-i-have-been-lucky-on-this.html http://http://catb.org/gpsd/gpsd_json.html
I'm interested in the following fields (condensed from table by George Theotokis in first reference above). The python library typically returns "nan" (Not a number) when values are not present. Note these properties are available from the gps.fix object.
| Name | Always returned? | Type | Notes |
|---|---|---|---|
| mode | Yes | numeric | 0=no mode value yet seen, 1=no fix, 2=2D, 3=3D. Used to determine if GPS has a fix. |
| time | No | string | Time/date stamp in ISO8601 format, UTC. Might use to set system clock and/or for logging |
| lat | No | numeric | Latitude in degrees: +/- signifies West/East. Present when mode is 2 or 3. |
| lon | No | numeric | Longitude in degrees: +/- signifies North/South. Present when mode is 2 or 3. |
| alt | No | numeric | Altitude in meters. Present if mode is 3. Don't care for this project |
| track | No | numeric | Course over ground, degrees from true north. |
| speed | No | numeric | Speed over ground, meters per second. |
| climb | No | numeric | Climb (positive) or sink (negative) rate, meters per second. Not used on this project |
| epx | No | numeric | Longitude error estimate in meters, 95% confidence. Present if mode is 2 or 3 and DOPs can be calculated from the satellite view. |
| epy | No | numeric | Latitude error estimate in meters, 95% confidence. Present if mode is 2 or 3 and DOPs can be calculated from the satellite view. |
| epv | No | numeric | Estimated vertical error in meters, 95% confidence. Present if mode is 3 and DOPs can be calculated from the satellite view. |
| ept | No | numeric | Estimated timestamp error. Present if time is present. |
| epd | No | numeric | Direction error estimate in degrees, 95% confidence. |
| eps | No | numeric | Speed error estimate in meters/sec, 95% confidence. |
| epc | No | numeric | Climb/sink error estimate in meters/sec, 95% confidence. |
- Controlling servos via the Polulu servo controller
- Interfacing to the Adafruit combined compass accelerometer Adafruit LSM303DLHC, including tilt corrected compass
- Using the I2C interface
- Interfacing to a AS5048B rotatry shaft encoder via I2C, for a wind direction sensor