diff --git a/README.rst b/README.rst index 09cacf7..f662a9c 100644 --- a/README.rst +++ b/README.rst @@ -41,7 +41,7 @@ Feather boards and many other circuitpython boards will round to two decimal pla >>> float('1234.5678') 1234.57 -This isn't ideal for gps data as this lowers the accuracty from 0.1m to 11m. +This isn't ideal for gps data as this lowers the accuracy from 0.1m to 11m. This can be fixed by using string formatting when the gps data is outputted. @@ -88,7 +88,71 @@ These two lines are the lines that actually solve the issue: print('Latitude: {0:.6f} degrees'.format(gps.latitude)) print('Longitude: {0:.6f} degrees'.format(gps.longitude)) - + +About NMEA Data +=============== +This GPS module uses the NMEA 0183 protocol. + +This data is formatted by the GPS in one of two ways. + +The first of these is GGA. GGA has more or less everything you need. + +Here's an explanation of GGA: +:: + + 11 + 1 2 3 4 5 6 7 8 9 10 | 12 13 14 15 + | | | | | | | | | | | | | | | + $--GGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh + + +1. Time (UTC) +2. Latitude +3. N or S (North or South) +4. Longitude +5. E or W (East or West) +6. GPS Quality Indicator, + + * 0 - fix not available, + * 1 - GPS fix, + * 2 - Differential GPS fix + +7. Number of satellites in view, 00 - 12 +8. Horizontal Dilution of precision +9. Antenna Altitude above/below mean-sea-level (geoid) +10. Units of antenna altitude, meters +11. Geoidal separation, the difference between the WGS-84 earth ellipsoid and mean-sea-level (geoid), "-" means mean-sea-level below ellipsoid +12. Units of geoidal separation, meters +13. Age of differential GPS data, time in seconds since last SC104 type 1 or 9 update, null field when DGPS is not used +14. Differential reference station ID, 0000-1023 +15. Checksum + +The second of these is RMC. RMC is Recommended Minimum Navigation Information. + +Here's an explanation of RMC: +:: + + 12 + 1 2 3 4 5 6 7 8 9 10 11| + | | | | | | | | | | | | + $--RMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,xxxx,x.x,a*hh + +1. Time (UTC) +2. Status, V = Navigation receiver warning +3. Latitude +4. N or S +5. Longitude +6. E or W +7. Speed over ground, knots +8. Track made good, degrees true +9. Date, ddmmyy +10. Magnetic Variation, degrees +11. E or W +12. Checksum + + +`Info about NMEA taken from here +`_. Contributing ============