code/breadcrumb/client/consts.py

   1 # -*- coding: utf8 -*-
   2 """ Useful constants for Breadcrumb client-side programs.
   3
   4 Sentence offsets for parsing sentence strings
   5 See http://www.gpsinformation.org/dale/nmea.htm for an explanation on all sorts
   6 of NMEA sentences, not anywhere near limited to those used in this application.
   7
   8 SENTENCE_OFFSETS: The keys can be a bit terse, so here's the explanation:
   9   - lat_fl, lon_fl: floating point values for lat, lon (pretty raw)
  10   - lat_ns, lon_ew: hemisphere (north/south for lat, east/west for lon)
  11   - time: self-explanatory
  12   - velocity, velocity_kt: velocity in m/s, knots
  13   - heading: true heading
  14   - m_var: magnetic variation
  15   - m_var_dir: direction of magnetic variation, set(['E', 'W'])
  16 """
  17
  18 DEFAULT_THRESHOLDS = ( # Push a new point when...
  19     ('heading',   15),  # ... we turn 15 degrees or more,
  20     ('distance',  500),  # ... or we travel 500 meters or more,
  21     ('timestamp', 1200),  # ... or twenty minutes pass (heartbeat).
  22 )
  23
  24 SENTENCE_OFFSETS = {
  25     'GGA': {
  26         'time':   1,
  27         'lat_fl': 2,
  28         'lat_ns': 3,
  29         'lon_fl': 4,
  30         'lon_ew': 5,
  31     },
  32
  33     'GGL': {
  34         'time':   5,
  35         'lat_fl': 1,
  36         'lat_ns': 2,
  37         'lon_fl': 3,
  38         'lon_ew': 4,
  39     },
  40
  41     'RMC': {
  42         'time':   1,
  43         'lat_fl': 3,
  44         'lat_ns': 4,
  45         'lon_fl': 5,
  46         'lon_ew': 6,
  47
  48         'valid_rmc':   2,
  49         'velocity_kt': 7,
  50         'heading':     8,
  51         'm_var':       9,
  52         'm_var_dir':   10,
  53     },
  54 }