I’m a civil engineer from Canada and am familiar with high accuracy survey / trimble equipment. I have been a surveyor in a past life, and currently manage the UAV / drone survey program for our offices.
I have tried some setups like what you are thinking about a 1-2 years ago: once using a Juniper Mesa 2 tablet running Windows 10, and once on a rugged android tablet with a paired GNSS receiver. I had limited success with the windows 10 tablet - although the issue was with the chrome browser, not AppSheet specifically. Basically, the windows 10 tablet had two methods for getting GPS coordinates - through the cellular network, or the installed precision GPS hardware / COM Port. Unfortunately, the only browser that would read from the COM port was internet explorer (barf). The android tablet worked, but required additional steps prior to taking GPS readings as the GNSS reciever would go to sleep after some amount of inactivity.
Basically, expect to encounter headaches on the hardware side of things and definitely do some testing prior to purchasing anything.
Now, with respect to AppSheet specifically:
- AppSheets reported accuracy seems to cap at 3m in the horizontal, even if the hardware is getting better than that. So, you can’t really trust it in these sorts of setups
- AppSheet only records the horizontal plane - no elevation
- AppSheet saves lat/long to 6 decimal places on the horizontal - this can provide you 10cm of precision… But if you need to be this precise, you likely also want elevation data.
With all the above said, my conclusion is do not attempt this sort of setup currently with AppSheet. Even if you managed to get it working, AS simply does not provide enough reassurance that your GPS signal is true and accurate. If you are really needing sub-meter or better accuracy, then I would look into ESRI options for building forms such as Survey123 or ArcGIS Online. These products are tailored to GIS / surveying workflows and requirements.