LS RTN user wants to add UHF/Base

[jahalnon]

Was wondering what other users get in fix times and accuracy between using an LS with a base receiver compared to the RTN setup?

Been using the LS through smartnet for over a year and a half now and have been very satisfied but also still cautious of use in thick canopy. From what I have been gathering from others is that the LS run through a base(T1 or T2) would get me better z's and more reliable x,y under cover.

Thoughts?

Thanks
John

 

[Matt Johnson]

It will largely depend how far you are from the closest physical base used in the RTN solution. The shorter the baseline length, the more accurate solution. The spec sheet for the LS states the accuracy as:

This of course is from testing in open sky locations. Under tree canopy the accuracy will degrade.

 

[Adam]

One of the biggest advantages to using a Javad base is the ability to get redundancy with the post processed rover points.

 

[jahalnon]

Most of my work lately has been local and we have an RTN base that is 6 miles away. Always considered that lucky. But even when using best practices in canopy I never fully trust the shot especially when we have overlap with shots from a total station (wetland flag locations). Some shots have been proven unusable.

I guess I was wondering if it was worth adding the base and uhf connection if it can diminish the unusable points due to post processing capability as Adam suggests.

 

[Adam]

How long are you observing the points?

 

[Adam]

The additional ppk points are a priceless check. It's not to say you won't have some disagreement between the rtk and ppk now and then in canopy, if they dont agree then you know you need to check it.

 

[jahalnon]

I try to use the Boundary setup and let it cook but at a minimum I use the Precise Topo and let it sit until done.

 

[Jim Frame]

Constellations are another consideration. I use CRTN (California) a lot, but it's GPS-only, so things go much faster when I use my own base.

 

[jahalnon]

Thanks guys.

 

[jahalnon]

So yesterday I went into canopy, 80-90' red oaks, maples and some white pines and in 4 hours was able to get verified fixes and duplicated
shots on 12 important features (24 shots total). I utilized "Precise Topo" and left it to do its thing until done. It would take 3-10 or even 15 minutes per shot.
Once I got deeper and thicker, there were places where it was not going to happen.

So my real question is about productivity. My guess is with the addition and use of a base receiver in the open field that I had access to, my productivity for getting those shots would be better and time required would be quicker. Thoughts?

 

[Sean Joyce]

The closer the base is to your site the better off you will be. A tough shot will be made tougher by the use of an RTN with base stations not close to the site.
I have been fortunate lately to be within 2-4 miles of a CORS base on 3 surveys and the L.S. did pretty well. On one
there was a 1/2 hour period where my local base went off line and my base went to the next closest which was about 20 miles away and the performance was awful, even in fairly open areas with only a few obstructions. In the picture I did a survey within 600 feet of my local CORS. (shown in the background) That survey really cooked. I double and triple my shots and average when only using the RTN. How close was your base to your job?

 

[jahalnon]

6 miles, which is pretty good. But I do get jobs that go 15-20 miles.

 

[Matthew D. Sibole]

The biggest downfall of not having a javad base and rover is not being able to use DPOS.

15-20 miles is too far in my opinion to get good repeatable data from an RTN. Yes it might tell you it is fixed but try checking into that fix tomorrow and see how close you are. (In my area 40 miles to the nearest CORS, I am lucky to be repeatable within 0.25'.

 

[jahalnon]

One last equipment question; I have the cell modem/sim card on the LS. If I buy the base receiver, do I need to send the LS in to get the uhf modem installed?

Thanks

 

[Matthew D. Sibole]

You can use TCP corrections with your base. You would need to get a hotspot at your base with a static IP. I use a UHF radio because my cell phone coverage is terrible here. If you have good cell coverage then TCP is the way to go.

In this scenario all you would need to purchase would be a T2 with RTK and a Verizon MiFi or similar.

 

[jahalnon]

Awesome, thank you all for your help.
John

 

[Phillip Lancaster]

If I was in that type canopy I would only use Boundary profile.