so ive been messing with APRS for a few months now and overall its been pretty cool but theres something thats been bugging me. my position on aprs.fi shows up consistently about half a mile from where i actually am. im running a TM-D710G in the truck with the internal GPS and ive double checked that the GPS is locking fine — it shows like 6-8 satellites usually when i check the menu.

at first i thought maybe it was just aprs.fi doing some kind of averaging or caching the last known position or something but even when i drive around and let it update a bunch of times its still consistently off in the same direction, kind of to the northeast of my actual spot. its not random jitter, its like a fixed offset which is weird to me.

the digi i'm hitting is about 12 miles away if that matters. running 1200 baud standard AFSK. anybody seen this before or know what might cause a consistent offset like that?

that consistent offset thing is usually a datum issue or sometimes a display glitch in how aprs.fi renders the coords. the D710G internal GPS should be outputting WGS84 which is what everything expects, but worth double checking your GPS settings in the radio menu — there's a geodetic datum setting buried in there somewhere and if it somehow got set to something other than WGS84 that would explain a fixed directional error like you're describing.

also just to rule out the obvious — are you sure the lat/lon in your beacon is formatted correctly? the APRS position format is picky about degree/minute encoding and ive seen radios that had slightly wrong configs spit out coords that look right on the display but are subtly wrong when decoded. you can check the raw packets on aprs.fi by clicking the raw data tab and manually decode a position to verify. if the raw coords match where you actually are then its a display issue, if they're off then its coming from the radio config.

half a mile is actually pretty significant for a fixed offset, yeah that does sound like a datum or encoding problem rather than GPS accuracy. my old handheld used to do something similar and it turned out i had the position manually set somewhere in the config that was overriding the GPS lock — took me forever to find it. might be worth doing a full reset on the radio and setting up APRS from scratch just to rule out some weird config conflict.