RTK Base VS. RTK CORS network
Hello community, I am hoping that someone can clear some information up for me real quick. Our office use the Trimble R10 head unit and we run off our states cors network which works out for establishing control and getting on grid. However, if i go the the same control different times of the day or a different day of the week there are h & v inaccuracies. I was tasked to find out if we got another head and set up a base station would I be able to use this form if RTK, which would still be tied to the state plane coordinate system to remove these inaccuracies. I have no experience with stations so i cannot shed light of the subject. I use the RTK cors to get control and run with a robot, but we are looking to use our gps more heavily for topo.
> would I be able to use this form if RTK, which would still be tied to the state plane coordinate system, to remove these inaccuracies
In my experience, Yes you will see better numbers (but maybe not by much).
Using our local Trimble VRS network we were seeing unexplained jumps in height of about 75mm (that's 3 inches for metricly impaired).
We have abandoned VRS, and now only use RTK.
If you search this site you will some discussion of the topic in other posts
The use of GNSS is always a little confusing - the result of a measurement is affected by many things and needs to be validated - averaging measurements over time is a good way as most systems are designed to be -/+ 2cm or an inch - even though the stored coordinate has it to four decimal places. Taking two gps shots 100 feet apart can have a large error ( maybe a tenth or more) and is always affected by length of baseline, canopy, weather, solar storms, electric wires and other things that affect radio transmission. It is best to use the right tool for the project, if you only need data to the tenth of a foot and there is little canopy cover GNSS works well - otherwise use the GNSS to set control 1800+ feet apart and then run through it with a total station to refine the values and collect the data - you can expect it to be +/- 0.02 that way
Using a base helps with the length of baseline, but you need a license to broadcast from the FCC ( in the US ) for more than 1 watt and that might be good for 1000 feet
Having a clear view of the southern sky helps with measurements too, any hills, wires, trees will all affect the signals from the satellites and degrade measurements, but know that in the best cases you might get +/- 0.05 in the vertical since the signals are traveling 24 miles to get to your receiver
new to the site, but will try to help...
The differing solutions at different times in the day is most easily explained by saying you are picking up signals from a differing constellation of satellites at different times of the day (there may be some other stuff going on but that is common). A base/rover setup will allow (in most cases) for your vector lengths to be shorter, which in turn should allow for less residuals in the measurements (which in most cases will help with the precision of the measurement).
It sounds like you maybe a construction user, so as far as accuracy. You set your base up on a known project control point, this will reference you to the project design. Assuming all the control and design data have been verified by a qualified person.
The best way to check the accuracy you are getting with VRS is to stakeout points you have shot at other times and note the differences. You are probably seeing +/- differences in vertical when comparing with total station i.e one control point could be +20mm(or more) and another -20mm(or more) resulting in a 40mm difference. Least squares can be your friend.