I apologize if this has already been answered.
I read through the forums and im still not sure on these points.
My application is setting up GCPs for mapping, and also laying out field plots, both in an agricultural environment. I am thinking to obtain two Reach RS+ units, one as a base and one as rover. The base position will be established using PPK. Where I am operating there are continuously operating reference stations available, with the furthest distance being 30km, but generally the distance will be much less than that.
So I have three questions, how long will my base have to log data to obtain cm precise ppk solutions? I know the specs say 1hr, but i am wondering if that time requirement changes with more distant cors.
Second question, given the parameters of my work, would there be any advantage to using two reach RS2 units instead?
Third question, the base might be used in the future for guiding tractors if we ever get gnss tractor guidance systems. Would reach RS+ be satisfactory for that purpose?
That depends if you want to have absolute or relative accuracy. From how I read your post, you want absolute.
Generally, the longer you observe, the more precise and accurate (and thus trustworthy) the observed point will be.
You mention you will have several CORS available, my advice would be to use all of them for processing, so you have some means of checking that one of them doesn’t give you a wierd result. You can then average out the position, using the baseline length for each station as a weight (or use EzSurv that does it all automatically).
That depends on your required accuracy in the end result and on how close your nearest CORS is.
The longer the baseline, the more precision is lost (stdev getting larger).
Using your own base, you decide the baseline, and thus the accuracy (to the extent of how the base-position was derived). Your rover results would have a much lower relative stdev against your own base, compared to if you derived your rover data off a nearby CORS (but farther away than your own base).
With your own base, the chance of solid fix is also higher.
It depends on your budget. Is the RS2 that much better? Yes it is! Much more resilient to vibration and to radio-noise. Is also even better build, with the pro-user in mind.
Thanks for the advice. On the first question, often our sites will be a long drive away so we can’t collect base data for hours and hours. Just to give me a rough idea of precision, what would be typical precision i could expect of a ppk result using a cors that is, say, 20 km away with one hour of observations only? And yes, we want absolute positions. Also clarification on question two, im wondering about two RS+ vs two RS2.
For PP static mode, the RS2 will, according to the specification, give you:
H: 4 mm+0.5 ppm V: 8mm+1 ppm
For 20 km, that is 4mm+10mm=1.4 cm horizontal and 8mm+20mm=2.8 cm vertical.
For the RS+ (Where 20 km is on the very limit for a single frequency receiver):
H: 5 mm + 1 ppm V: 10mm + 2 ppm
For 20 km, that is 5mm+20mm=2.5 cm horizontal and 10mm+40mm = 5 cm.
Mileage may vary, and observation time might need to be longer, especially on L1-only.
