Aprs.CompressedPositionHelpers (aprs v0.1.5)

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Compressed position helpers for APRS packets.

Summary

Functions

calculate_compressed_ambiguity(arg1)

Calculate position resolution (ambiguity) from the compression type byte.

convert_compressed_cs(cs)
convert_compressed_lat(lat)
convert_compressed_lon(lon)
parse_compression_type(arg1)

Parse the compression type byte to extract all encoded information.

Functions

calculate_compressed_ambiguity(arg1)

@spec calculate_compressed_ambiguity(binary()) :: integer()

Calculate position resolution (ambiguity) from the compression type byte.

In compressed format, the compression type byte encodes:

  • Bits 0-1: GPS fix type/NMEA source
  • Bits 2-4: Position resolution
  • Bit 5: Old/Current GPS data

Position resolution values:

  • 0: No resolution specified (full precision)
  • 1: 0.1' (about 600 feet)
  • 2: 1' (about 0.01 degree)
  • 3: 10' (about 0.1 degree)
  • 4: 1 degree

convert_compressed_cs(cs)

@spec convert_compressed_cs(binary() | nil) :: map()

convert_compressed_lat(lat)

@spec convert_compressed_lat(binary()) :: {:ok, float()} | {:error, String.t()}

convert_compressed_lon(lon)

@spec convert_compressed_lon(binary()) :: {:ok, float()} | {:error, String.t()}

parse_compression_type(arg1)

@spec parse_compression_type(binary()) :: map()

Parse the compression type byte to extract all encoded information.

Returns a map with:

  • gps_fix_type: NMEA source/GPS fix type (0-3)
  • position_resolution: Position ambiguity level (0-4)
  • old_gps_data: Whether this is old GPS data