Single Frequency GPS

try "nrcan". they use precise point positioning, a different approach than standard gps processing. natural resouces canada will process the single frequency data for you. i beleieve ashtech solutions will also process single frequency

You need some post-processing software, like Ashtech Solutions. Drop me an email.

when we had single frequency units I would often download the CORS data and add that to the solution. more often than not, I would simply run the two simultaneously starting and ending on a control point. the first time i did a 'loop', my last point was 0.01' horizontally and 0.06' vertically from the first point. The best part: I had 6 legs in the loop, just added a hundredth per leg. granted, i did let the units cook for 45-60 minutes per leg.

Go with GNSS Solutions from the Ashtech Website. It lets you automatically connect to CORS Stations via the VRS module to build into your solution. See:

https://surveyorconnect.com/index.php?mode=thread&id=121387#p121393

And here's how to it. You should get pretty good results with two hours worth of data, even L1, assuming you have CORS stations reasonably nearby.

http://www.ashgps.com/ms/GNSS_Solutions_FAQ/GNSS_VRS_RevA_20100521.pdf

You really need some training to become familiar with GPS, I would suggest taking a training course in whatever post-processing software you decide upon.

:good: :good:

I would second the training.

OPUS will not work with single freq. GPS.

Processing against CORS will work, if you have a CORS station nearby. 15-20 miles is pushing it for L1 data (even with hours of data), so the CORS station must be close.

The best way to tie into V & H control, with L1, is to let a unit sit on a nearby NGS control point (with good open sky) while you "Rove" with other units. Three units is better because you form an adjustable triangle with each set of observations. Two units doesn't have much in the way of "checks". If the control point is <5 miles away, you'll probably need to let your Roving units sit for 30-45 minutes.

Then you post process the data in something like Ashtech Solutions or Ashtech GNSS, both of which are free on the internet for the L1 only versions. But the software is where you might need some training, because it's easy to go wrong.

I agree using local control is the best and would add you should have at least two control points of known x,y,z. Then do as you say, but do it again with the base on the other control point, so all your points are double occupied through at least two separate control points. I think the standard is at least 50% are double occupied, but I always do all of them.

That said, I have to agree with Mark Silver that the VRS functions in the Magellan software deliver some surprisingly good results.

Nothing like the speed and precision of the Trimble VRS Now network with a new R8 and a TSC3 with Access. That stuff's really amazing.....but of course it's dual frequency and thousands of dollars more expensive.

Definitely Go With GNSS Solutions And VRS

Once you are set up, it is easy to let it pull in the CORS data for you.

BTW, unless you are close (12 miles or less) to several CORS you will soon want to get a third PM2. 3 receivers more than doubles your productivity, plus it gives you confidence in your positions especially at longer range. I had 2 PM2s to start with and within a month I bought a third.

Paul in PA

Does the VRS thing in GNSS work with the PM 2? Or Locus? The link refers to using it with PM3. But, I guess data is data, as far as post processing goes. I have downloaded GNSS and I might give the VRS thing a try with my Locus. That's a very interesting link, and if I understand, it says they are getting fixed solutions from miles away with a 15 second observation (L1 only)? That's pretty amazing, and worth looking into for sure.

Definitely Go With GNSS Solutions And VRS

Hey Paul,

Can you only use the VRS thing in GNSS with stop & go, or can you also use it with traditional static methods (i.e., turning the receiver off between locations?) I was thinking about giving it a try with Locus, but I don't have the "stop & Go" kit for that. I was thinking about giving it a try with 10-20 minute observations, then turn off and move to the next point.

VRS In GNSS Solutions Questions

Yes to both questions. I have used it with static files from ProMark 2s.

It uses the raw PM2 positions to pick XYZ values for a Virtual base point within your project. It then grabs data from 3 surrounding CORS and creates a virtual observation file out of thin air. You then solve your PM2 files in L1 only from a very close base station. For very short vectors the L1 only solution is often more precise than the L1/L2 solution. Several times over the years I was not getting a good solution between L1/L2 and L1 receivers so I disabled the L2 and got better results.

You can also take the virtual file that was created and convert it to a RINEX file. Using a "none" antenna model and 0.00 antenna height you can submit it for an OPUS solution.

Since I have L1/L2 receivers I don't use VRS regularly, but some day I will get on a job far far away with dead L1/L2 batteries or some other such glitch. For control on a small job I typically set up 2 L1/L2 receivers and a PM2. I always have all 3 PM2s with me so when that happens I can keep on working. On a bigger job I will use all 5 or maybe even more.

Paul in PA

VRS In GNSS Solutions Questions

Thanks Paul. I'm going to give VRS in GNSS a try with some old static data.