Need some idea's or advice

R.Perry · May 22, 2021

How do you map a dam face. DD will do vertical or horizonal, but will not do angles such as dam faces.
Any ideas or suggestions

MapMaker53 · May 22, 2021

Wouldn't flying a grid pattern over the horizontal extent of the dam (as in an aerial view) result in a 3D angular surface model? I assume the dam face has a significant slope and is not simply vertical. What type of slope does it have? From the scale and area of it in the photo, it looks like it could be 45-60 degrees.

MapMaker53 · May 24, 2021

Alternatively, and this would take a bit of planning, you could set up your own back and forth Litchi waypoint mission in the form of a mapping grid or grill across the face of the dam - across the slope - keeping a consistent altitude above the dam face as you move across it and change locations. You would want to aim the camera perpendicular to the dam slope during the entire mission, whatever angle that might be. Naturally, for mapping waypoints, the traverses would need to be fairly tight to provide overlap of the images. I would use the aerial grid/grill produced by a mapping software just as a general template for setting up the waypoint mission, just to get an idea of the needed density. The only question would be if Litchi can be set to take continual photos at timed intervals. I've never explored that aspect and am not familiar with it. If that works, then simply upload the resulting set of images to your mapping service for processing.

Another consideration in this approach would be the arc of the dam, which would require some additional waypoints along the traverses. Would be an interesting and challenging project.

R.Perry · May 24, 2021

I could measure the slop, or get it off the engineering drawings. I think your estimate is pretty close. I've never seen a dam with vertical sides. This is only one of three that I need to map.

MapMaker53 said:
Alternatively, and this would take a bit of planning, you could set up your own back and forth Litchi waypoint mission in the form of a mapping grid or grill across the face of the dam - across the slope - keeping a consistent altitude above the dam face as you move across it and change locations. You would want to aim the camera perpendicular to the dam slope during the entire mission, whatever angle that might be. Naturally, for mapping waypoints, the traverses would need to be fairly tight to provide overlap of the images. I would use the aerial grid/grill produced by a mapping software just as a general template for setting up the waypoint mission, just to get an idea of the needed density. The only question would be if Litchi can be set to take continual photos at timed intervals. I've never explored that aspect and am not familiar with it. If that works, then simply upload the resulting set of images to your mapping service for processing.

Another consideration in this approach would be the arc of the dam, which would require some additional waypoints along the traverses. Would be an interesting and challenging project.

With Litchi you can set timer for photos. Now for the math, speed, verses photos per seconds. Need to think about this one.

kabonski · May 24, 2021

Haven’t flown a DJI for a while but if it had GPS lapse as a photo option you could use that. On the unit we fly the GPS lapse works both horizontally and vertically so we can fly vertical flight lines up and down a dam or cliff face and snap pictures at a set distance apart. You would just need to do some calculations to get the proper overlap for mapping.

RamSchulz · May 26, 2021

Maybe check out Drone Harmony - they are mapping mountain slopes - a little similar?

Drone Harmony

But it is another software platform, that you have to pay for...

Gr8Basin · May 29, 2021

If you utilize Pix4D capture, you can fly it manually with set photo interval (horizontals & vertical). You can then dictate how far away from you/dam face and fly the face, then move to the next level down and repeat until you get sufficient coverage.
I’ve also made use of the SiteScan Lite (free) app to design an oblique mission that allows you to do a really good mission area design. It allows for angle compensation of slope, overlap and custom polygon for area of interest. It does a really good job, EXCEPT that it’s not so stellar on the manual override if something comes up mid-flight. Pix4D allows for the mission to paused and operator assume control of the drone, whereas SiteScan just pauses the whole mission and leaves your drone hovering unless you completely abort the whole mission. Then the app control sends your drone home. I personally don’t like this feature, and if I were in the same situation of flying a dam face, probably would use the app sparingly.
ive had really positive results flying manually with P4D, and SiteScan, but I prefer P4D.