Post pics of difficult shots

Shawn Billings

Shawn Billings

Shawn Billings
5PLS
@Adam I used to hate cut over when I first started surveying. Seems we'd get called to survey about 5 years after it was timbered. Plenty of briars and scrub elm and sweetgum and rotting tree tops. Worst stuff in the world for traversing through, especially this time of year (August). Plenty of ground bees to stir up when you are cutting through. Lots of hot sun and no shade and no breeze. Now it's like a gift. All I have to do is get through it and I have open skies for the RTK to work from. Funny how things change.
 
Adam

Adam

Well-Known Member
5PLS
Here's a KML file I exported from Jfield directly. Pretty handy feature right there. Vegetation height is around 20 to 30ft tall but small diameter. The site looked to be timbered about 10 years back.
 

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Adam

Adam

Well-Known Member
5PLS
By the way 133 is one that RTK had trouble with it is bad, but I know it's bad;). This point is directly north of a 12"pine about 6 inches and in heavy pine canopy. On 133 I had some 10 minutes of static and only got a few RTK epochs. The PPK for 133 agrees with the RTK and PPK of 136.
 
Adam

Adam

Well-Known Member
5PLS
My new crew chief locating a gas line.
KIMG0364.jpg
 
Wes Cole

Wes Cole

Active Member
Jim Frame said:
That looks like a tough location, but it begs the question: what kind of results did you get.
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It was a difficult location and a very meaningful tie to a survey I'm working on. Would've taken an hour or more to traverse to it. Meant to add a note of my results but got side tracked this evening.

I took two 200-second observations and worked through all 3 phases under that black pine. The two stored points compared 0.04' horizontal and 0.02' vertical.
 
Nate The Surveyor

Nate The Surveyor

Well-Known Member
I have been doing the same things. TRYING to get a lie out of the LS.
So far, with much effort, I can get a PPK shot that is lying. Not alot, but I did 3 observations of a PPK type, With no radio. They were of the 5-6 minute variety. The First, and last agreed by a few hundredths. The middle one was out by 0.20' from the other two.
I am thinking that in the really bad stuff, a PPK shot HAS to be some 15-20 minute long, and HAS to be repeated. Or, if it is critical, maybe even 3 observations.
N
 
Shawn Billings

Shawn Billings

Shawn Billings
5PLS
In bad canopy, you are correct Nate. Don't trust a single PPK solution and for the best chance of success collect for at least 15 minutes.

I believe the worst verified RTK repeat observation I've seen has been 0.16 foot horizontal and probably 0.3' vertical. The vast majority of the time, I have less than 0.10 foot horizontal agreement between two verified RTK positions in difficult canopy, and typically less than 0.06'. Yesterday I took a shot on a really tough point under a 48" oak tree (it was less than 10 feet from me to the Southeast) with a lot of other trees around. I took two shots. They agreed to a tenth. I had shot this point with a total station traverse from GPS control adjusted with least squares about 4 years ago. The coordinates of the average from yesterday were hundredths from the 4 year old survey.
 
Nate The Surveyor

Nate The Surveyor

Well-Known Member
My point is a WARNING, to Javad users, who are used to getting great data, with RTK, in 5-10 mins. THEN using PPK, and ASSUMING that a single 10 minute observation, IN CANOPY is solid. It's not.... some of the time. The protocol for PPK is not fully resolved, FOR CANOPY SHOTS. Except, to say, IF IT MATTERS, do it 2 or more shots. And, do them for 15+ min each. You do not have a way to fully QC a woods shot.... without repeat observations. As Shawn said above, RTK Repeat in the canopy, he has not seen yet more than 0.16' RTK difference. Well, PPK can be worse in canopy.

Nate's rule for now: PPK, in canopy, MUST be at least 10 min per observation, and MUST be repeated, if the shot really matters.
Until more information.... or further development....
Nate
 
Darren Clemons

Darren Clemons

Well-Known Member
Shawn Billings said:
In bad canopy, you are correct Nate. Don't trust a single PPK solution and for the best chance of success collect for at least 15 minutes.

I believe the worst verified RTK repeat observation I've seen has been 0.16 foot horizontal and probably 0.3' vertical. The vast majority of the time, I have less than 0.10 foot horizontal agreement between two verified RTK positions in difficult canopy, and typically less than 0.06'. Yesterday I took a shot on a really tough point under a 48" oak tree (it was less than 10 feet from me to the Southeast) with a lot of other trees around. I took two shots. They agreed to a tenth. I had shot this point with a total station traverse from GPS control adjusted with least squares about 4 years ago. The coordinates of the average from yesterday were hundredths from the 4 year old survey.
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Totally agree with both Shawn and Nate here it's all about the redundancy and we've learned to use the PPK for redundancy on both shots we CAN get RTK on as well as ones we can't. If we get a finished 3 phase RTK that takes over 12-15 minutes, then we'll usually process that PPK data against the base afterwards to compare...most times, as Shawn says I'm getting less than 0.1 (in reality 90% are better than 0.04'!). For those few that the LS simply won't get any RTK on we're taking a minimum of two 15 minute sessions. That works as long as those 2 agree when processed, and we've almost always had them to do so within 0.05', but if you get to the base and/or office and process them and they DON'T then you have an issue. This is where Nate's desciption of having a third point is a must. Then, most likely, two of the three will match and you're good to go. With the combination of the six different engines, beast mode and now PPK processing from the rover, there are simply very few spots out there left where you can't get great, reliable, redundant, extremely accurate data. It may be two straight three phase RTK shots in an unreal heavy canopied spot in 8 minutes or it may be two or three PPK points that takes an hour, or some combination of the two. The LS was the best RTK system on the market before the addition of PPK, but that feature has taken it to a completely different level!
 
Darren Clemons

Darren Clemons

Well-Known Member
IMG_1377.JPG
Ok, here's one I got by "accident" this week. Just crazy....I was following an existing survey and this point called for the pin at the base of this 28" black oak. When I got to the tree, I leaned the LS against it while I kicked around the base looking for the pin. When I found the pin, I went to grab the LS and noticed the screen....6 full engines and staking right to where the pin was!! The pin was right up against the base of this big boy and the LS barely had room to plumb up. No problem - I had my full three phase RTK (repeated twice with 0.03' difference) both within 5 minutes.
 
Adam

Adam

Well-Known Member
5PLS
Darren Clemons said:
View attachment 6319 Ok, here's one I got by "accident" this week. Just crazy....I was following an existing survey and this point called for the pin at the base of this 28" black oak. When I got to the tree, I leaned the LS against it while I kicked around the base looking for the pin. When I found the pin, I went to grab the LS and noticed the screen....6 full engines and staking right to where the pin was!! The pin was right up against the base of this big boy and the LS barely had room to plumb up. No problem - I had my full three phase RTK (repeated twice with 0.03' difference) both within 5 minutes.
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Absolutely amazing where the LS will work.
 
Adam

Adam

Well-Known Member
5PLS
This one took me about 30 minutes to set and feel good about it. Summer is the most challenging season for ussurveyors. We are dealing with thick vegetation and lots of critters and bugs. One thing I have noticed while using the LS for boundary work is I don't seem to stir up as many bees as I would if I were using the robot. Its usually the second or third pass thru that gets them in a tizzy. With the robot and one man you cover the same ground five times. With the LS you cover it once.
IMG_20170621_125811657.jpg



Thanks @Javad
 
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