A question for GNSS gurus:
Say you have a GPS only base receiver setting in a wide open field on top of a hill, sending out RTK correction messages.
At the same time you also have a GNSS rover acquiring observations from GPS/GLONASS/Galileo/BeiDou/QZSS satellites, and this receiver is set up in a not so open area. This rover is receiving RTK correction messages from the base.
Regarding the correction message stream sent to the GNSS rover, would it be true that the correction message mostly instructs the GNSS rover as to a bearing/disrtance/slope angle to shift its coordinates in order for the coordinates to be correct? And, if true, wouldn't this mean that the corrections sent from the base would likely be substantially the same identical bearing /distance/slope angle correction regardless whether the base itself was acquiring satellite signals from all 5 systems?
Or, does each GNSS rover constellation require its own separate correction message in order to use that constellation in the solution, and the base can't send it if the base can not generate it?
Just trying to make sense of what it would mean to have an expensive multi-constellation base receiver sending out correction messages as opposed to having just a cheap GPS only base.
Thanks
I'm no guru.
I believe it is corrected on each satellite individualy. Thus, the more sats the base tracks, them the more is contained in the data stream, via radio link, or whatever method.
All these corrections, are collected at the rover, and assembled into a rover location, of varying accuracy, depending on many factors. Multipath, distance from base, satellite geometery, etc.
You'll get a better answer from others.
N
The rover is doing the corrections and it can only use common satellites. Only GPS satellites will be used for RTK in that situation.?ÿ
the only corrections you are receiving from the base are based upon the satellites that the base can utilize. Your rover being able to utilize additional satellites will not be taken into account. ?ÿ
Thanks all. Back about 20 years ago it was explained to me by a company salesman that the base computed and streamed instant vector correction messages, in order to "move" the instant autonomous rover positions back in the reverse direction so its coordinate would be correct (of course, assuming base coordinates themselves were actually correct). I thought if that was true the vector wouldn't hardly be any different whether it was computed from an open field GPS?ÿ only determined coordinate or whether it was computed using additional constellations. I guess what everyone is saying is that the base doesn't really determine a correction vector at all(?). All these years using RTK I never really gave it much thought especially as my base and rover were always matched receivers/antennas. This question has only come up recently as more and more constellations are coming on line, and the question of saving a little money on the base came up.
ibenhavin
?ÿ
The base is the "dumb" machine. You tell it where it is with the DC at start up. Then it broadcasts a signal that tells anyone listening what its position is, which satellites it is connected to and the data it receives from them time stamped. The rover looks at the same data and "corrects" its postion using the base numbers as the fixed close position. The base isn't really sending a vector correction. The rover is doing all the calculations. You can turn both receivers into dumb machines, we call that static surveying and figure out the answers on the PC later.