Utilities

class aprspy.utils.APRSUtils

Useful generic functions for APRS parsing and decoding.

This class provides functions for parsing and decoding different kinds of APRS packets. Packet type-specific functions are defined under the different APRSPacket subclasses.

static decode_compressed_latitude(latitude: str) → float

Convert a compressed latitude string to a latitude value.

Parameters

latitude (str) – a latitude in a compressed format

Compressed latitudes have the format YYYY, where all values are base-91 printable ASCII characters.

See also APRS 1.01 C9 P38.

static decode_compressed_longitude(longitude: str) → float

Convert a compressed longitude string to a latitude value.

Parameters

longitude (str) – a longitude in compressed format

Compressed longitude have the format XXXX, where all values are base-91 printable ASCII characters

See also APRS 1.01 C9 P38

static decode_dfs(dfs: str) → Tuple[int, int, int, Optional[int]]

Decode a DFS (Omni-DF Signal Strength) value and return the individual values.

Parameters

dfs (str) – a DFS value, minus the initial DFS identifier

The DFS extension provides a way of specifying approximate values for:-

• Received signal strength (in S-points)

• Antenna height above average terrain (in feet)

• Antenna gain (in dB)

• Directivity (in degrees)

Like PHG values, DFS values are 4 characters long, and each digit is responsible for one of the above values. The APRS spec does not specify it, but it is assumed that - like the PHG value - the antenna height can be any ASCII value from 0 upwards.

See APRS 1.01 C7 P29

static decode_nrq(nrq: str) → Tuple[Union[float, str, None], Optional[int], Optional[int]]

Parse an NRQ (Number/Range/Quality) value and return the individual values.

Parameters

nrq (str) – an NRQ value

For direction-finding reports, the NRQ value provides:-

• The number of hits per period relative to the length of the time period (as a percentage)

• The range (in miles)

• The bearing accuracy (in degrees)

NRQ values are 3 digits long, and all digits from 0 to 9. An ‘N’ value of 0 implies that the rest of the values are meaningless. An ‘N’ value of 9 indicates that the report is manual.

The bearing accuracy represents the degree of accuracy, so a ‘Q’ value of 3 is 64, meaning that the accuracy is to less than 64 degrees.

See APRS 1.01 C7 P30

static decode_phg(phg: str) → Tuple[int, int, int, Optional[int]]

Decode a PHG (Power, Effective Antenna Height/Gain/Directivity) value and return the individual values.

Parameters

phg (str) – a PHG value, minus the initial PHG identifier

The PHG extension provides a way of specifying approximate values for:-

• Power (in watts)

• Height above average local terrain (in feet)

• Antenna gain (in dB)

• Directivity (in degrees)

PHG values are 4 characters long, and each digit is responsible for one of the above values. As per the APRS spec, the height value can be any ASCII character from 0 upwards.

See APRS 1.01 C7 P28

static decode_timestamp(raw_timestamp: str) → datetime.datetime

Decode a timestamp.

Parameters

raw_timestamp (str) – a string representing a timestamp

Timestamps can take a number of different forms:-

• Zulu, identified with a trailing ‘z’, which refers to zulu time

• Local, identified with a trailing ‘/’, which has no timezone information

• A hour/minute/second timestamp without any date information

static decode_uncompressed_latitude(latitude: str) → Tuple[Union[int, float], int]

Convert an uncompressed latitude string to a latitude and an ambiguity value.

Parameters

latitude (str) – an uncompressed latitude, in the form DDMM.HHC

Uncompressed latitudes have the format DDMM.HHC, where:-

• DD are the degrees

• MM are the minutes

• HH are the hundredths of minutes

• C is either N (for the northern hemisphere) or S (southern)

MM and HH can be replaced with spaces (” “) to provide positional ambiguity (C6 P24).

See also APRS 1.01 C6 P23.

static decode_uncompressed_longitude(longitude: str, ambiguity: int = 0) → float

Convert an uncompressed longitude string to a longitude value, with an optional ambiguity level applied.

Parameters

• longitude (str) – the longitude, in the format DDDMM.HHC

• ambiguity (int) – the level of ambiguity, between 1 and 4

Uncompressed longitudes have the format DDDMM.HHC, where:-

• DD are the degrees

• MM are the minutes

• HH are the hundreths of minutes

• C is either W (for west of the meridian) or E (for east)

Positional ambiguity is handled by the latitude, and so should be honoured regardless of the precision of the longitude given (as per C6 P24).

static encode_compressed_latitude(latitude: Union[float, int]) → str

Convert a latitude to a compressed latitude value.

Parameters

latitude (float/int) – a latitude

Compressed latitudes have the format YYYY, where all values are base-91 printable ASCII characters.

See also APRS 1.01 C9 P38.

static encode_compressed_longitude(longitude: Union[float, int]) → str

Convert a longitude to a compressed latitude value.

Parameters

longitude (float/int) – a longitude

Compressed longitude have the format XXXX, where all values are base-91 printable ASCII characters

See also APRS 1.01 C9 P38

static encode_dfs(strength: int, height: int, gain: int, directivity: int = None) → str

Encode a DFS (Omni-DF Signal Strength) value from individual values.

Parameters

• strength (int) – the received signal strength, in S-points

• height (int) – the antenna height, in feet

• gain (int) – the antenna gain, in dB

• directivity (int/str) – the antenna directivity, in degrees, or omni

For more information, see decode_dfs().

static encode_phg(power: int, height: int, gain: int, directivity: Union[int, str]) → str

Encode a PHG (Power, Effective Antenna Height/Gain/Directivity) value from individual values.

Parameters

• power (int) – the power, in watts

• height (int) – the antenna height, in feet

• gain (int) – the antenna gain, in dB

• directivity (int/str) – the antenna directivity, in degrees

For more information, see decode_phg().

static encode_timestamp(timestamp: datetime.datetime, timestamp_type: str = 'zulu') → str

Encode a timestamp.

Parameters

• timestamp (datetime) – a timestamp

• timestamp_type (str) – the timestamp type (zulu, hms or local)

static encode_uncompressed_latitude(latitude: Union[float, int], ambiguity: int = 0) → str

Encode a latitude into an uncompressed latitude format.

Parameters

• latitude (float/int) – a latitude

• ambiguity (int) – an optional ambiguity level

For more information see decode_uncompressed_latitude()

static encode_uncompressed_longitude(longitude: float, ambiguity: int = 0) → str

Encode a longitude into an uncompressed longitude format.

Parameters

• longitude (float) – a longitude

• ambiguity (int) – an optional ambiguity level

For more information see decode_uncompressed_latitude()

static generate_passcode(callsign: str) → str

Generate an APRS-IS passcode for a given callsign.

Parameters

callsign (str) – a callsign, with or without an SSID

This will generate an APRS-IS passcode for a callsign, after stripping the SSID (if given).

classmethod validate_passcode(callsign: str, passcode: str) → bool

Validate an APRS-IS passcode for a given callsign.

Parameters

• callsign (str) – a callsign, with or without an SSID

• passcode (str) – a passcode

This will generate a passcode for the given callsign, and compare it to the provided passcode.