I’m writing from Croatia and using the RTK Facet to get approximate locations of my land parcels. I downloaded the official parcel coordinates from the Croatian State Geodetic Administration (files: .shx, .shp, .prj, .dbf) and imported the layers into SW Maps. The RTK Facet is connected to SW Maps via Bluetooth.
The issue I’m seeing is a consistent offset of about 1–2 meters from the actual marked points on the ground. I have several points that are professionally surveyed and marked, and when I compare, the positions are always off by the same margin.
The satellite status looks good — the RTK Facet reports accuracy of <20 cm, and SW Maps also shows low latitude/longitude error and low horizontal/vertical accuracy. At first, I suspected my coordinate data might be incorrect, but I had a professional surveyor test the device with his own reference points, and he observed the same offset.
Am I missing something in my setup or configuration? Any suggestions or guidance would be greatly appreciated.
Great response that it’s the Reference Frame. If you where to take measurement from each property corner (like the surveyor did, assuming they used GPS/GNSS receiver) using your device and compare them to a recorded map or deed, you would likely see that your bearings and distances closely match up with the record. Depending on what GPS/GNSS service you are using, such as a Real-Time Network RTK corrections service or using your own base station and Rover, they are different ways to arrive at the correct answer. The quickest answer is derived from the Real-Time Network because the measurements are shared with the service provider and then the service provider corrects your current Epoch date coordinate and translates the coordinate to a reference frame epoch date that is widely used in your region. I’m in California, USA and we use NAD83 (2011) EPOCH 2010.00 as our reference frame. Check out what yours is in Croatia.
The longer answer for using your own base and rover requires a lot of software and knowledge of how the earth’s continental shifts are moving in your region, which I will spare you the already lengthy response from being any longer. Hope this explaination helps.