Static GPS in canopy

With a pair you could set up one in the clear and one in the questionable location and let them cook while you use your usual rover on RTN for other points.?ÿ Postprocessing later will give you the best shot at a vector between the stationary pair. If the rover will record short static sessions while also doing RTN, so much the better, and provide an improvement in relative positioning of your points by virtue of the short baselines.

I find multiple hours, 4+ preferably, works best. And Bill is correct, having at least one in open sky is necessary.

deciduous trees are the least troublesome, they are generally shorter so shorter sessions often will work.

@bill93 Three receivers is the minimum I would suggest and ideal for setting coordinate pairs under canopy to go back with EDM for layout. Three units also allow for efficient leap frog traversing. However I suggest leaving one unit in wide open area that is free from canopy for your entire session. Then move only unit at a time leaving atleast two collecting data simultaneously. This will help to maximize common SV's. If you can see decent daylight at your location then you can get good static results with 1 hour occupation. Dense forested areas of conifers that block sunlight should be avoided. In this area set coordinate pairs at the south edge to traverse into later with EDM. Good luck.

These are excellent tips!

Exactly the sort of conversation I was hoping for.

I do not thank ($) Wendell nearly enough. ?ÿNot nearly enough.

I've got an idea. (Grin) ????

Nate

Brad, I've got 5 L1 locus 8 channel static receivers. Paid 3500 each for 1st 3. 3500 for all of the next 3. One got hit by a car.

I've run lots of network with them.

As others said, one in the open, all day long. As you set each one out, give it a score.?ÿ

My score system was:

1.) It'll get it in 1-2 hrs.

2.) It'll get it in 2-4 hrs.

3.) It'll get it in 6-8 hrs.

And, I was experimenting with 20-30 hrs. I learned alot this way.

Nate

Do you guys put them on 2-m poles with the hold-a-pole and tripods, or tripods with tribrachs, or just 2-m poles with bi-pods, or other? ?ÿIs it important to get good measure ups from the point to the gps head even if I care not for vertical on just boundary work?

If you don't care about the elevations, crude measure-ups will be plenty good for your near-horizontal vectors.?ÿ Set up the antennas on anything you want so long as you can plumb over the points of interest.

2m poles with bipod or pole tripods. Never used the hold a pole devices. Verticals tolerances will be high in canopy. Also I suggest 10 second epoch rate on old recivers with limited memory.?ÿ

I use Hixon poles, seco Bipods.

Write down slant height.?ÿ

Reciever number

Start time

Stop time

And point description.

This way, all correct vectors will close with tight tolerances.

N

Brad,?ÿ

Have a stroll here:

https://kb.unavco.org/kb/category/gnss-campaigns/11/

Then take a look at this file:

https://www.rics.org/globalassets/rics-website/media/upholding-professional-standards/sector-standards/land/guidelines-for-the-use-of-gnss-in-surveying-and-mapping-2nd-edition-rics.pdf

Lots of great information within..

@stlsurveyor That looks like it maybe useful on West coast. Very few stations on the east coast.?ÿ

But that reminds me. Brad don't forget to add a few of your closest CORS stations into your post processing network.?ÿ

At first you should Constrain just one CORS, both horizontal and vertical. Then verify the accuracy of other CORS with ngs data sheets. Once satisfied you can constrain more. This will build confidence.?ÿ

Mission plan it for a 25 degree horizon to find the best times. I found that there were shorter 45-90 minute windows that would process better than longer occupations. If you can request a RINEX file of near-zero baseline VRS from your local RTN to process against, it's easy to get three solutions that agree to a tenth.

?ÿ

@dave-karoly Back in the day when all we could do was static. I had three Trimble 4000se receivers. One like you say, was placed in an open area. The other two were leap frogged around to corners in the project. You could monitor what satellites the receiver was reading, it's azimuth, and the signal strength. In heavy trees positions, we developed a technique we called the "Mechanical Blow Down". It consisted of a chainsaw, a energetic Sawyer and someone monitoring the GPS unit and directing the Sawyer as to which trees had to go. The unit was left for a minimum of two hours while the third unit was being positioned.

I had very good luck with this technique. Only had one disgruntled landowner when we cut a lone pine down, because it was shading the corner.

Time is money, trying to locate/set a pin directly under a dense pine tree is often very time consuming. Usually there are a number of close by points that can be observed and then the pin can be taped in. Depends on the task, but locating three points <10' from the position in a couple of minutes opposed to hours of static observations and processing is usually a no brainer. What type of point under a tree needs static?

Under a tree, especially a conifer, that usually takes a pair of control points. Of course top of a ridge is easier than down in a canyon. If I have to hike a half mile to the corner through steep and difficult terrain Iƒ??d rather set up the receiver and collect it directly than set a pair and have to bring a total station to tie it. The current project weƒ??ve been lucky, the three monuments that require a pair and angles/distances are right next to roads, one is in a campground. The hiking corners have all been open enough, a few are WFO (wide Fing open) courtesy of a fire in 2020.

If you are solo, and need to set a pin under a big pine, here is a handy procedure.

You've already got your hammer, and some pins, right?

Evaluate, and decide what goes where. Set rebar, in the open (temporary), and take shots on them. Then inverse to corner, and use swing ties to set rebar corner. Then, depending on things, after setting corner, hook tape on corner, and put gps to stake the corner, and double check from any direction.?ÿ

Things should fit less than 0.05' if you got it right.

Unless you've got a Javad. And then that thing will work almost anyplace.

N

?ÿ

When surveying in dense Adirondack woods like this?ÿ43.7753456,-74.4089721 (Turn on Satellite view.)

I doubt your Javad would be able to set pins within tolerance.

I'm not enthusiastic about this strategy of cooking static on a location where RTK isn't fixing. Basically you are rolling the dice hoping enough satellites to fix will pop up at some point if you let it cook long enough. Sure, I understand that you can static fix with fewer birds than with RTK, but not that many fewer.?ÿ In this day and age of multiple constellations there really aren't the PDOP holes and spikes that there used to be, so the chance of the strategy working is less than it might have been OUAT.?ÿ ?ÿ

You can give it a shot, of course. But I rate the chances of success to be about 1 in 3.?ÿ

I'd prefer to set 3 temporary controls using RTK nearby in the open a then resect a TS position to tie the monument. That requires dragging the TS out and takes a lot more time, naturally. But it may save you a deployment.?ÿ ?ÿ ?ÿ?ÿ

Another thought - the data collectors I am familiar with can be set to record points when coordinate quality reaches a threshold. Leave your RTK cooking on a point while you do other stuff and hope that, at some point, enough satellite pop up to fix, reach that threshold, and record.?ÿ ?ÿ?ÿ