Code/Float points in a creek/drain......

[Darren Clemons]

I was in a spot yesterday that was just horrible (not to mention the heat index was 102!). There's just not many spots this Javad will not get, but we were shooting the meanders of a deep drain on a farm and it was in such a deep "V" bottom ravine, we could only get 7/8 Sats at any one time, therefore not much luck with RTK.
I haven't tried this much but toyed with it yesterday on this spot and wondered if anyone had any settings suggestions.
For these "meanderings of the drain" shots my deed called for, I would be more than happy with Code/Float (CDF) shots I believe. From what Shawn and others have said these are much, much more accurate (1' to 2') than the standard "float" shots (3' to 6'). I first went to settings and allowed shots for "fixed, float, DGPS", then turned off my UHF radio so the LS would only be reading CDF (although a few times it wouldn't even give me that it would go to stand alone (STN)). Then with epochs set to 120 it would collect 2 minutes of data averaging the shots as it went. I collected 3 separate shots this way on the same point and they were within about 2.5' of each other.
There was some discussion similar on collecting Dpos sessions. Are three separate 2 minute shots "averaged" better than one 6 minute session?
Has anyone used the CDF to collect anything similar to this and what were the settings and time duration you prefer?
Of course, there aren't many spots I'd be satisfied with this accuracy, but this drain is about 25' wide from bank to bank with the "thread" being at least 6' wide in itself. Meanders like this would not be shot or located exactly the same by any two surveyors anyway so I believe Code/Float collected points would work well.

 

[Adam]

I've located some creeks and gulleys and wetlands with cdf similiar to what you are doing, I also at the same time ran a compass traverse between the cdf float points and tied into some better points for a check. I was in the deep woods and I saw some of them were around 8-10' off, this was tunneling thru overgrowth from the creek banks. 1-2' is in the open accuracy for CDF. CDF seems more stable in the woods then a float or standalone no question. I set on the points for 5 minutes but the creeks were more narrow than yours.

 

[Darren Clemons]

I've located some creeks and gulleys and wetlands with cdf similiar to what you are doing, I also at the same time ran a compass traverse between the cdf float points and tied into some better points for a check. I was in the deep woods and I saw some of them were around 8-10' off, this was tunneling thru overgrowth from the creek banks. 1-2' is in the open accuracy for CDF. CDF seems more stable in the woods then a float or standalone no question. I set on the points for 5 minutes but the creeks were more narrow than yours.

Good info Adam. 8'-10' might be ok just for location purposes but would be too much for bndy lines, even in rough drains such as I'm describing.
Would still be useful in many situations especially for recon work and generally locating fence lines, etc

 

[Matthew D. Sibole]

I would suggest turning the Waas profile on and editing it to store raw data and have a minimum of 15 min. I would then use dpos to give me a solution. I would probably do that 2 times just as a check for each meander point.

 

[Shawn Billings]

I don't trust float solutions, period. I know some do and that's there business, but I do not.

A code float is useful in certain applications. I would not trust a code float to be much better than 15' in canopy. It can certainly get down to a couple of feet in the open, but once you get under trees all bets are off.

 

[Matthew D. Sibole]

I agree Shawn, that is why I would want to DPOS it and hope it gets a fix and why I would take two shots to check the first one.

 

[Bob Farley]

Darren,
I usually will tape a perpendicular offset of a constant value on my side of the ditch/creek, set nails and locate the offsets , say 50' to the thread of the stream. At each end of the ditch, where the boundary comes straight into the ditch I set a rebar at that same offset and again where the boundary leaves the ditch, then you can tie a vector course & distance between the rebars so that any competent surveyor can reproduce your ditch/creek boundary.
I agree with Shawn and Matthew, I have had unverified fixes be off 3 or 4 feet in hostile environments, usually thick pine trees.

 

[Darren Clemons]

I don't trust float solutions, period. I know some do and that's there business, but I do not.

A code float is useful in certain applications. I would not trust a code float to be much better than 15' in canopy. It can certainly get down to a couple of feet in the open, but once you get under trees all bets are off.

I never have either Shawn in the past nor will I now based off what you guys are telling me. I'd just read/heard talks of the CDF being so much "closer" than normal float solutions and hadn't tried/tested it. I will almost always do something similar to what Bob describes setting rebars on each end where the meanders can be tied in.

Wouldn't do the 2x fifteen minute dpos for each meander point at all. Over 30 minutes each would be way too much time to devote to meander points. Sometimes there's still just spots to get out the gun and run it.

 

[Shawn Billings]

The CDF is probably superior to float, but only in open spaces. CDF is better than standalone (autonomous) in canopy too. But it's not submeter in the trees most likely.