Quote:
Originally Posted by GH85Carrera
(Post 10689892)
The targets are large white X shape targets that make it simple for us to see that point, and tell our computer this is X,Y & Z and accurate to a very high accuracy (sub MM) since they used a Trimbale GPS or some other brand that gave them super accurate measurement. We ask for a grid of them, in a pattern, and we will be well within the map accuracy standards.
|
Accuracy:
I was sold this Topcon system I am using now on the basis it would provide me with the accuracy I wanted which was 0.02' to 0.03' horizontal, I was told I would get close to the same vertical, that would be a lie.
I also discovered something horrifying while using it. Just holding the pole in human hands can result in inaccuracies of up to 0.10' or greater. I needed better than that.
Here is my 16 y/o (when he was 15 earlier this year) running it locating utilities and fences. I taught him how to run it in about 15 minutes. Which makes me sad as any idiot can be a land surveyor now.
https://photos.smugmug.com/photos/i-...-2LCBntz-L.jpg
Once I realized we humans cannot hold the thing steady enough to obtain real accuracy, I purchased some carbon fiber bipods to mount on them. Now we can lock the unit in place and keep it there. We use the bipod mount for any location requiring high tolerance. Then we programmed to the GPS to take thirty separate one second observations then average them out.
https://photos.smugmug.com/photos/i-...-PfL4GXs-L.jpg
We will sit on a property corner or nail in the road for 30 seconds using the bipod locking it into place. We are finally achieving 0.02 or better accuracy horizontal.
Vertical? Not so much I have to use a level to get good vertical, it is wanky at best, I see 0.1' to 0.3' variations all the time. Sometimes it is within 0.01' others it is out to lunch at 0.30'. I am a 1 man crew so I keep a laser level in my truck to use when I need high accuracy like an FFE staked on a house.
What made me realize we were NEVER very accurate was the fact that the pole can move so much, using a standard total station with a prism pole it would not be so noticeable. If we were going for a tight closure we would be using tripods and running a closed loop, turning multiple angles (typically reverse) and taking multiple distance readings.
When we were laying out houses and locating form boards, or even setting corners, I realized just holding a prism pole can result in 0.1' or worse accuracy. This was realized when using the GPS.
The addition of GPS has been a godsend, my next 2 purchases for my company will be a robotic total station then out of left field, a Prius V for my second crew to drive. I realized they are 99% on the pavement in residential settings. I am the one on the construction sites all the time. So the other crew is ditching the 20 MPG pickup truck for a 40+ MPG Prius.
The robot will compliment my GPS so I can truly be a 1 man crew. Right now I sometimes have to steal a guy to help me or take the prismless instrument and set up prism poles on bipods for backsights. Which I have to do next week to do a tree survey. The robot will eliminate that. Plus the robot runs off the same Win10 tablet I am using for my GPS utilizing the same software, I just have to pay to unlock the capability.