California Surveyors Forums

Working on a wild hair idea and need some thoughts and input.

I would like to gather topo data and be able to have an end product that was geo-referenced, and 3D. This would be of an existing lake bed and river channel. The purpose is to enable the location/marking of hazards that are dependent on the current water level. The end product would have to be electronic database in a portable unit to enable the user, based on current position and elevation, (water level) be warned of hazards/potential hazards, or enable an agency to flag hazards as the water level changes.

due to the lack of water, this is a once in a lifetime chance to map the bottoms of many lakes, some which have not been seen since the dams were built in the 1920's.

What are your thoughts/ideas/pros/cons of aerial photogrammetry vs. lidar vs. ??.

this is open discussion to help me solidified a jumble of random thoughts.

Potential project is approx. 2-4 miles wide and 25 miles long and not even close to being a rectangle.

Thinking Horz. of +/- 1-2' and Vert. of +/- 1-2'.
the next step will be to identify a funding source.

Thanks

Drone.
Contact me for an example.

Aerial mapping, drone or otherwise, should do just fine with collecting what you're looking for. You may need to get closer to ID certain things. Sounds like a GIS application of the data is what you are looking for. As you raise or lower the water elevation, certain features (rock outcroppings, etc.) are exposed or are now more than 6' below the surface.

Great idea Russ.

I would research the application/software to use in the boat before you solicit proposals. One of the machine control (dozer mounted) type systems could be adapted for what you want to do. The available formats for the plan/ground model will drive what your deliverable will be.

1" = 40' scale photogrammetric mapping generally supports 1' contours and is cost effective. Some of the accuracy is dependent on the control accuracy and how much time they spend on collecting break lines. I usually build some independent on-the-ground checks into the workflow to ensure we get the desired accuracy. If the ridges surrounding the lakebed are 1800' or higher, it could get problematic to fly with a fixed wing aircraft.

You will want to have a GPS controlled image capture platform to minimize ground control

Lidar ends up being noise-ier data. Likely the data can support a +/- 2' accuracy surface model.

Drone mounted image capture systems will have more inexpensive cameras than the million dollar photogrammetric mapping cameras and will have to be flown much lower with less ground coverage. You will have to evaluate the proposals as this could be a cost effective solution too.

Sounds like a great project to work on. Will we see an article on this when you are finished with it?

thanks for the responses. just more random thoughts.

Main issue is the timeframe. Need to gather data soon, before (fingers cross and doing rain dance) the lake refills.
Challenge is the lake is within a "V" shaped canyon that varies in width at high water, from 1/2 mile to 3 miles wide. The bottom width is unknown as it has been under water since 1924, best guess is approx. 200-300 ft. wide. The depth is 400-500 feet at the dam 300-400 feet at the midway pt. The headwaters is at the bottom of a canyon that is 1000'+ feet deep.
Secondly with the above constraints, how to establish the control.

I am not that familiar with the drones, but I am guess due to the area to be covered, the drone will be limited. this project would cover approx. 25 miles of steep canyon bottom.
Even if the data can not be released, it is a opportunity to gather the data.

Lastly, need to find that magic funding pot.

Russ,

You might check with the Irrigation District. they will be interested in bathymetric data for capacity of the reservoir. This could be a source of funding for you.

Finnaly got in direct contact with an engineer at the Irrigation District and they are mapping the area for another reason, (potential dam expansion), and he is willing to share the data, so now the challenge will to be to secure funding to review the data and format to the users.