sdi-12 issue

hey guys, new to the forum and the Arduino so go easy.

i have a project im working on for an irrigation/agricultural company as part of my own companies contracts to them. i need to track movement of a system within a paddock. i already have a telemetry system on the device thats moving that operates on a radio mesh network. the hardware takes data off multiple instruments and sends them to a base and downloads everything into a database for data extraction.

ive been playing with the arduino and adafruit gps module in my office and ive got as far as getting the raw gps data from the adafruit in the coms window. the company that makes the telemetry hardware want me to get the arduino to output 16 bit modbus data for all the variables but that i think is clunky. the unit also accepts SDI-12 and i already have other instruments talking on the SDI-12 channel which works great.

question is what would i need to do to get the arduino and adafruit giving a SDI-12 string output. if i could have lat, long, elevation, bearing heading, speed as my string output that would ideal, i can then have the software that strips the database coded so each variable is put in the correct place for web presentation.

the reason i want to use this telemetry option vs cell phone is the radio version is free and the farm already has the radio network set up.

look forward to some help.

cheers

Ben Walden