I didn't think of that approach, thanks!!!
Using a Baofeng with custom OpenDM32 firmware, I was able to view raw NMEA packets from the GPS module. The transceiver was near a window, and the satellite level and number were low. As you can see, the deviation is quite large, requiring software filtering.
Yes, I concur. The deviation I've been experiencing is quite large. I've seen fixes that were nearly a quarter mile away.
I implemented some filtering on the Map Display page I'm working on, and it corrected much of the drift. There is still drift, but it is much tighter. As you would expect with higher-end GPS hardware, it is now within about 20 feet or so.
The Leaflet map does not zoom in closer than, I'd guess, about 500–750 feet, so you now just get a blue blob representing the drift. I think I introduced a bug on the page while doing some other unrelated work, and my history trail isn't displaying, or I'd have a screenshot to share showing the difference. Once I track down that bug, I'll have some comparison images to post. I'll also try to summarize the filtering code so I can share what was done to tighten the displayed drift.
I should note that the code does not fix the drift on the radio itself—it only tightens the displayed fixes on the back-end map. So it's more of a workaround band-aid than a true GPS drift solution for the radio. The radio's GPS is still sending wildly divergent fixes, but now the map averages the fixes over a time limit and a speed factor (less than 2 mph) to clean up the trail display.
As I said, I have a bug somewhere that killed my history trail function, and I'm still having issues sending fixes upstream from the hotspot to the backend server when they are not on the same LAN. I'm considering implementing a VPN between all the components. This could also strengthen data security between them over the internet.
I'm just not sure how well the Pi Zero W will handle running a VPN, SQLite, and the normal hotspot functions at the same time. I'm planning to pick up a Pi Zero 2 W soon and give it a try on better hardware. My goal hardware for the final project would be a Pi 5, but I have to work with what I have for now due to a tight budget.
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Да и смысл. 
