This is a page consisting of some detailed notes taken during the process of getting APRS message construction and transmission working.
This is my attempt to give back to the general community which has done a lot of work in this area already.
There is a lot of information on the web, but pretty scattered, and not always as clear as could be.
I (Doug) am a software developer by trade, and I think some of the specifics relating to building messages could be made clearer in a number of cases.
In this page, I will attempt to provide:
The multiple layers of protocol that constitute APRS
How to build those messages
Including specifics on APRS Checksumming (FCS), which I found particularly difficult
Specific binary-level detail on a complete and valid APRS message that you can check against your own implementation
Links to resources I found helpful
NO Broad overview of what APRS is - you can find this elsewhere