My question is about collecting and processing Promark2 (or 3) data in GNSS Solutions for Stop-and-Go initializing with the 20cm kinematic initialization bar.
Base station is set up with the 20cm initialization bar attached and given a point number. The rover is attached to bar and initialized for 5 minutes with a different point number noting in the unit that the rover is on the bar. Then I detach and rove, the rover point number incrementing with each new point collected.
Am I correct in thinking the data collected while the rover is on the bar will produce a point 20cm from the base, that it stays 20cm from the base through processing with GNSS Solutions and that the first "useful" point is the first one off the bar.
If I set the base and rover to collect at 2 second intervals, is a good time to stay on each roved points 20-30 seconds, which would give 10-15 epochs? More? Fewer? A different collection period?
A Minute
Till you set up and make appropriateiate notes of your position you've been there a minute, use it all. With a PM3 and Blade processing you could live with less time but why waste any time you are at a location?
Paul in PA
For the dim recesses of my mind regarding Ashtech and its heirs and assigns:
Most of my customers considered the kinematic initalization bar as more of an unnecessary nuisance than a necessity for initialization of the PM2 or PM3. Either of those receivers will initialize just as well on a point of unknown relative location if you bump the time on site up to about 7-8 minutes. The advantage of the bar is that it gives the software a precisely known distance between the points which aids in solving the ambiguities of the relative positions between the base and the rover. The disadvantage of doing the initialization with the bar is that you have to fool with the bar and the risk of displacing your base receiver setup by the jostling of the setup while dismounting the rover antenna from the bar. If you are going to use this gear, I think it is best to put the base on a tribrach for stability's sake.
The key to understanding how long to occupy a point in stop and go mode is that you must have one more data source than the number of elements you are trying to solve for. When you add the kinematic aspect, that adds the time element like it does for RTK so that you are solving for x,y,z and time, meaning that with kinematic applications you must have at least five epochs of data to solve the position of the rover. Just like RTK. And more is better, to a degree. At a 2-second interval, you get 7 or 8 epochs depending on how the clock hits with your starting the timer on the point.
Much longer than the recommended minumum 15 seconds may or may not really be any better because the post processing software is computing the vectors for every epoch, including the ones recorded between your time on a particular point. So even though it does not show you the solution for all those single epoch points, they are considered by the software to maintain a fixed position solution.
The most important advice I could give you about stop and go operation is to be certain to occupy a defined point periodically that you can come back to in order to reinitialize should your rover lose kinematic lock. It is important to tag these point as "Control" in the collection screen before logging them. The only practical effect tagging these point as control has is that the receiver accumulates a list of the Site IDs that you have identified at control and the receiver will allow you to reoccupy the point using the same Site ID, which it will not if you have not designated the point as a control point.
Sorry this got a bit long but if you are going to do Stop and Go failing to do a couple of simple things that you may not know to do could make your whole session a waste of time. And the bad thing about Stop and Go is that you do not know what sort of results you have until you are done and process the data.
Hi Tyler,
The init bar is 'b' 's'. Just do a couple of minute shot on any random point to start a S&G session.
Earlier versions of GNSS Solutions (and Ashtech Solutions) were not nearly as good as the latest version. With the current version I have shot three 30-second points, with a total file length of 2 minutes, 1.7 mile baseline back to the base and gotten FIXED solutions.
The important thing (in my opinion) is to make sure the recording interval is 1 second on both the rover and base. I can't tell you how many jobs have been ruined by having 10 second observations with 15 second intervals.
M
Mark is right. Been a couple years since my last stop and go session but we had a very reliable system. We set a point inside 1000 feet from the base (generally much closer - within 100) and log it first for 5 min. Then go to work. Provides aa reinit point for later. Never failed us yet. Stop and go is a lot of fun in open sky. Those receivers are so light for all day topo work.
We do occasionally use the bar but we use it to test vertical offsets with new antennas to make sure they match up with our other receivers. We've got quite a few flavors so the init bar makes a nice lab tool for making sure our results will be consistent.
Thanks All
Tried the bar yesterday and didn't have a good experience. I'll try a separate point when I get a chance.
I'd better review the procedure too as the Promark wanted to do a 30 sec then the 300 sec init.
