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4 GPS
TH-D72A/E CONTENTS 25
The latitude and longitude information required by the GPS receiver does not allow for accurate
representation of the unevenness of the Earth’s surface. For use with GPS, the current standard that
defines the precise shape of the Earth is called WGS-84. By using this standard in conjunction with
mapping standards for each country, accurate position plotting on a map can be done.
Although position can be described in many different formats, such as degrees, degrees and
minutes, and degrees, minutes and seconds, the GPS system and APRS have standardized on the
degrees and decimal minutes format. Just like it is important to use proper international phonetics
when spelling on the air, it is important in APRS as in any communications system to have a default
standard for position. All operators should be trained to use the DDD MM.mm format by default in
voice communications just like in the data formats. Using these standards on the air will prevent
communications errors, confusion, repeats, and conversions.
APRS Standard:
4.1.2 Datum (Geodetic Survey System)
4.1.2.1 GPS and APRS Position Format
Geographic
Coordinates
Format Example
Latitude
DD MM.mm
(degrees and minutes)
39 49.31N
+39 49.31
Longitude
DDD MM.mm
(degrees and minutes)
84 15.39W
-84 15.39