i will be conducting a stop and go survey for an area extending upto 90km using Ashtek promark and GNSS solution as the post processing software and will like to confirm the following:
1-How do i obtain precise results at position extending beyound 10-20km from the base station.
2- How do i determine or assess the accuracy of the final result after post processing
That is a pretty far distance for an L1 receiver. I have never performed a stop and go survey, but you might want to double check the reliable distances that can be utilized using this method.
I use RTK on a regular basis, but notice that the farther my distances get from the base, the accuracy suffers.
I am no expert on the method that you are proposing, but think that might be pushing the limits.
Good luck, and please keep us updated.
Collect good static data between the base and project and then extend your static to the job. Use an on site static location for your stop and go. Kind of like traversing control into where it is needed. Sounds like you need to do some review of the manuals for the equipment you are planning to use.
jud
Jud gives good advice. I used this method many times while doing route type surveys with rtk for power line staking.
I did not think of that earlier.
As I recall, the promark stop and go function was pretty finicky. Even on small sites (less than 10 acres), it was not smooth sailing.
The range you are looking for seems to be much too far to really use stop and go techniques for. Even static observations would be questionable in the 90km range.
I would look for the possibility of establishing a control network using static observations in such a manner as to have much shorter baselines to infill with the stop and go methods.
From my experience with the stop and go function, you will need extremely extremely open sky view. If you loose initialization, you will need to re-initialize. Lose of initialization can occur just from getting too close to one tree in the middle of an open field.
thank you everyone. I was also planning on establishing temporary base stations at regular intervals of say 10km.once again thanks everyone....but i still have my second question unanswered. pls how do i check the accuracy of my final map/ CAD data
OK - Ill say it ...
It is clear you have accepted a job you are not qualified to do. You need some serious education / training before you do any more. And looking for this type of education on a public discussion forum is not the place to get it.
Turn the job over to someone that knows what they are doing.
Set a Static Control Point every 10 km. Observe these as a network, if you have 3 or more receivers or as a traverse if you only have 2 units. After you have your control inplace and observed, do a least squares adjustment on it. Make sure that you have sufficent redundancy. Now using these control points, observe the other points using the Stop and Go technique. IF you want to be able to hang your hat on the position of any of these points, occupy them twice with at least 2 hours of change in geometry. This should get you about 2 cm of horizontal accuracy and 5 cm of vertical accuracy.
One of the things you will almost certainly encounter is loss of kinematic lock with your rover receiver. There are a couple of by-the-book ways to reinitialize the receiver.
1. you can go back to your original initialization point. The problem with this is that you will likely have to travel back through the area where you lost kinematic initialization in the first place.
2. another method is to set points that you can go back to in the event of loss of kinematic lock as may be convenient. When you set these points, perhaps a setup nail or other such point that can be accurately reoccupied with your receiver, be certain to check the box in the point attributes screen that designates the site as a control point. Only then can you occupy that site using the original site ID assigned to that point. This tells the post processing software that the second and subsequent occupations are initialization(s).
Having indicated that a point is a control point when occupying it, you'll probably achieve better results if you occupy it for five minutes or more. Then to reinitialize on that point, select "Known point" from the initialization options menu. Note that until you have designated at least one point as a control point, the only options in the Initialization method box will be Bar and None. After tagging a point as a control point, the third method, "known point" will appear in the list.
