[aprssig] The best resolution of position from APRS

Tapio Sokura oh2kku at iki.fi
Tue Jan 3 08:32:34 EST 2006

Andrew Rich wrote:
> Which begs me to ask. What is the best resolution and how from the APRS 
> Spec ?

In APRS the best position resolution can be achieved with the base-91 
compressed format. With it you get a resolution of about 0.3 m in 
latitude and at least 0.6 m in longitude (on the equator). This is 
better than three decimals of minute, but less than four decimals. With 
regular uncompressed and mic-e you get a resolution of about 19 meters 
in latitude and at least 19 meters in longitude, again dependant on the 
latitude. This is exactly two decimals of minute.

So with the compressed format you get a 30-60 fold increase in position 
resolution. But do remember that resolution is not the same as accuracy, 
though you can't have good accuracy without good enough resolution.


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