Great news for those who have wanted drone RTK for centimeter level precision in doing mapping.
Currently, to get RTK with DJI, you need to spend over $5,000.
FYI. An RTK drone can obtain the GPS coordinates from satellites, but of course, due to plate tectonics the ground surface is constantly moving with respect to these coordinates. Surveys depend on the actual ground position, not GPSS coordinates. So, the satellite GPSS coordinates need to be corrected and this is done through signals from various RTK Base ground stations that are often linked to some network. For Califorina, this is the CRTN network:
So, if you have a drone that has an RTK module,it will be able to correct the satellite GPSS coordinates in real time, assuming you have access to an RTK network:
Do you have a list of free sources of RTK base station data in the United States? Compile here is a comprehensive list, applicable to all U.S. residents.
www.gpsworld.com
One thing about RICS is that they extend into surveying and mapping:
I have glossed over some details here. Maybe this helps:
1. Historical surveys use the latitude and longitude coordinates as of some date, according to the mapping system used at the time. We have NAD27 from 1927, NAD83 from 1983 (implemented 1986) and the currrent WGS84
Ellipsoids, survey benchmarks and triangulation - these are the ingredients for geodetic datums. NAD27, NAD83 and WGS84 are common datums in North America.
gisgeography.com
2. With WGS84, the coordinate system is centered on the earth's center of mass, the poles are where the earths axis of rotation intersects it surface. These are considered relatively stable points. However the WGS84 has been updated several times since its initial definition in 1984. For one thing, there is plate tectonic movement to account for. The plates move independent of the poles and center of the earth.
3. Satellites themselves have latitude/longitude errors that have to be corrected for.
4. So,for old maps, such as some that might have been created in 1930, you will have to correct for changes from NAD27 to WGS84, plus satellite corrections, with respect to legal issues. The old maps remain unchanged and always relevant at the source of boundary markers. But for any subsequent point in time, if legal issues come to the forefront, those coordinates will have to be mapped to the current mapping system, e.g. the current WGS84. In addition, if coordinates are obtained from satellites, then satellite corrections will have to be thrown in. It's complicated.
5. So, theoretically, RTK will do all of these corrections on the fly - assuming it has connectivity with some RTK Base Station Network. -- And that may be a problem. Some areas have only weak connectivity, not fast enough to support RTK in a drone. Instead, a RTK base station like the Emlid RS2 RTK GNSS Receiver, must be used to initially slowly acquire data, then broadcast that to the nearby drones. Such base stations can use internet, cellular broadcasting or satellite IoT systems such as Iridium to obtain correction data.
6. In the next to worst case, where there is no Iridium, internet or LorRa, then you scatter some markers (2x2 white boards with a black cross) at various location of the area you are mapping, get their GPSS coordinates, take your video and then back at the office, where it is assumed you have internet connectivity, make the GPSS coordinate corrections.
7. In the worst case, where you can't even connect to GPSS satellites at the survey site, you will have to find a a marker with known coordinates from some previous survey, a compass to place some N,S,W,E markers with respect to your base market - that you can include in your video - and make your corrections off that back at the office.
8. The best of all worlds is to have functional RTK on the drones, with a high precision RTK Base Station like the Emlid RS2. The RTK will pick up take some time to get a very precise GPSS set of coordinates and elevation, plus correction data for a specific market. An Emlid "Rover" can be used to further mark the GPSS coordinates of other markers placed over the survey area - and these then can all be picked by the drone's RTK module. It can be complicated.
I would expect that in Northern California, where I woiuld use RTK, all I will need is just RTK on the drone. IF I had to do mapping in very remote areas, then I would need an Emlid RS2 Base Station ($4000) [not likely].
