Under canopy observations

Hi I’m using the triumph ls with a base setup and am having trouble proving up under canopy observations. Good base spot, using the external antenna, sitting on the points for over an hour or more then processing it and trying to traverse between to prove it up and they’re just not fitting. By several feet. Applying grid to ground all that I don’t know what I’m doing wrong.
 

Adam

Well-Known Member
5PLS
More info is needed. I'd be happy to look at the project if you can post a link to it.
 

Nate The Surveyor

Well-Known Member
Who is your support person?
Do you have screen shots turned on?
Can you post a pic of your boundary profile?
Do you have a localize in it, on this job?

It seems you are new... Sorta. Have you run previous brands of GPS?
Have you processed gps through DPOS?
3' error sounds like a DPOS shift amount. Or, a wrong projection, like assigning the wrong SPC. Using a projection, a state or two away.
I'm personally a slow learner. But, I'm also persistent.
Nate
 

Nate The Surveyor

Well-Known Member
Ok, that leaves the potential of a bad shot. Maybe.
Was verify on? How many seconds between 1st and last fix, in the same group?
Since you ran a traverse, did you hit any other points? Ie, common gps, and conventional? If so, how did they fit?

Where are you in the world?

N
 
South Washington state yeah we hit the nw sec corner, west 1/4, East 1/4, se section corner, a couple 1/16ths and a couple control points all in the confines of one section. I’m just wondering if maybe I’m missing something in the settings. Several of the points I was just static under the canopy I’m wondering if for shots like that I should change the settings for example instead of only accepting rtk fixed maybe excepting everything for the dpos to sort through? Or turning my epoch count lower might increase accuracy? I’m missing something cause we used the same unit last year on a project spanning 7 sections with a lot of the control being under canopy and it turned out great. But the LS that headed that project basically took off as soon as it was through before I could pick his brain about it and yes I’m just starting to get into the more technical side of things. My firms old school though after he left I was basically tossed the javad and a Leica ts12 and said figure it out cause nobody else knew what to do with them lol. Mostly timber work other than my crew and so we’re trying to figure out how to utilize this gps to save time traversing everywhere to connect the dots
 

Nate The Surveyor

Well-Known Member
Ppk only, under trees, one hour of observation, is NO guarantee that it is a good shot. Rtk is stronger. (Mr Javad does not even agree with this, but, I'm pushing it, in the woods, and I and other users have the same results).
Why is it ppk, without rtk? What radio do you have?
N
 

Nate The Surveyor

Well-Known Member
Ppk, DPOS, under canopy.
Hard place to go back to. No radio. My "never return" solution is:
3-4 20 to 25 minute observations.
Post process, through DPOS.
You will wind up with at least 2 observations that agree, within a tenth, or such.
If you only do it twice, and they don't agree by some 3' or so, you don't know which is right. If you do it 3x, and 2 agree by a tenth, you probably have it. If you do it 4x, then you can be pretty confident that you have it. Often I'll have 3 out of 4, within 0.15', and 2 within a tenth.
Your mileage may vary.
Is this in a redwood Forest? Tall pine canopy? Does any rtk trickle through?
N
 

Nate The Surveyor

Well-Known Member
Nearly always, under deep dark canopy, I'm still getting some radio. As such, I'm getting some clicks. Once I get 3 clicks (with resets) , within 200 seconds, it is very nearly always 100% the right group. If I get 3 clicks, with resets, in 200 seconds, and 1200 seconds have gone by, (total), then for the most part, I know that is the right group, and, the 1200 seconds can provide the confirmation through ppk. It is usually something like 7 clicks, in 800 seconds. Thats a very solid group. I'll store it, and restart. It all depends on how critical a shot may be. If it's critical, I'll shoot it 3x. I tend to overdo it. But, nobody ever regretted a right answer.
N
 
Ok let me look at some things lol info overload. I will try looking at the rtk i was just going off the ppk then the cors. I will go out this weekend and try the multiple observations as well. Yes some of the locations I did get some groups of epochs it was mainly the ne sec quarter which we started our traverse at and the north 1/4 that were complete static but I think there might’ve been too much hill between me and the base. It’s like 50 year old Douglas fir sw Washington state.
 
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