Recommended Height and Overlap

[nwairphotos]

I'm using Map Pilot and Maps Made Easy and did a couple of tests, but I think I am getting much more detail than I really need and that's costing me a lot in points.

If, for example, I wanted to do a 50 acre quarry and be able to accurately determine volumes, what would be a good height and overlap? (for a P4P)

What about an orchard or vineyard?

I noticed that in the rendering some of the structures on the ground look a little funky. Does this happen with other systems as well?

 

[Richard R]

I was having some issues with my maps, MME recommended 80% or more overlap, which seems a bit much. On the Drone Deploy forum, pilots are reporting good results with 75%. Height will depend on what level of spatial resolution you want/need. I flew a similar area at just under 400 ft (keeping below the 400 ft limit for part 107 flights). Resulting 2 in or 5 cm pixels produced more than enough resolution and I could keep things under the 250 point level for no charge processing. Unless you add some obliques to the photo package, the sides of buildings, etc. are going to look, as you put it, 'funky' in the 3D view. And the edges may look a bit ragged in the ortho when you zoom in. Just part of the nature of the beast.

 

[nwairphotos]

Here's a map I made of part of a cemetery. I was low enough so that in the original photos the gravestones could almost be read. I'm disappointed it what happened to the roofs and also note that in the circular drive towards the bottom there's an area that's shifted. There are a couple of other issues as well. Is this normal?

Hawthorne Memorial Gardens

 

[Richard R]

No, definitely something wrong with your map. and your elevation map is all screwed up as well. Check out this example from one of my missions. Ladar 3 Mapping flight
What were your mission parameters (overlap, height, speed, etc.)?This was flown at about 200 ft AGL

 

[nwairphotos]

Thanks for checking that out. I think the height was at 200 feet but the data that I received after making the map said 300 feet which I'm sure is too high. I believe the overlap was 80% and I don't know about the speed. I thought that was something the program sets automatically. Do you think I could be at fault for the problems with this map? I did another mission that same day and that one turned out ok.

I checked you map and everything looks good and lined up just right.

I have been doing some experimenting with combining the photos in Photoshop, and they look a lot better. Is it possible to take a composite photo made in Photoshop and rubbersheet it to get similar results?

 

[Richard R]

You can double check your height by looking at the exif data in the photos. Read the first image (it should be the ground reference photo the MME takes automatically before it takes off). Then pick another image some where in the mission, read that altitude and subtract the reference value from the second. Result should be your height AGL. There are default values for them, but alt, speed, overlap are all user setable parameters. Two separate missions on the same day with the same bird and one looks good and the second one doesn't, I would first suspect your mission. MME records flight logs that you can download as a cvs file that you can read in programs like excel. May want to check it out. And double check all of your parameters (I record all of mine in my flight log). And if you save the two missions pull them back up and check out your settings. I've had issues with elevation maps using one of m P3As, but the ortho maps are always at least as good as the one I showed you. Don't know photoshop, so can't help you there.

 

[nwairphotos]

MME looked at it and agree there is something wrong. They refunded my points and made some suggestions but I might just do it over.

 

[Hammer]

we typically fly at 40m up to 90 m and do 75-85 overlap when dealing with engineering clients. they usually put down ground control points as well for their post processing. That being said ive had pretty decent results at 50-60 overlap for stuff that isnt that precise

 

[GVDD scout]

I was having some issues with my maps, MME recommended 80% or more overlap, which seems a bit much. On the Drone Deploy forum, pilots are reporting good results with 75%. Height will depend on what level of spatial resolution you want/need. I flew a similar area at just under 400 ft (keeping below the 400 ft limit for part 107 flights). Resulting 2 in or 5 cm pixels produced more than enough resolution and I could keep things under the 250 point level for no charge processing. Unless you add some obliques to the photo package, the sides of buildings, etc. are going to look, as you put it, 'funky' in the 3D view. And the edges may look a bit ragged in the ortho when you zoom in. Just part of the nature of the beast.

Have any experience which is better: 1. Set a flight altitude based on surrounding terrain for required GSD, and fly a 2nd mission for an AOI inside, i.e. a pit or a large stock pile, at an altitude that keeps the mean surface the same distance away from the camera then use both sets of images for processing. Or 2. fly a single mission with altitude for GSD in the AIO, and thereby limit the number of points?

 

[cskeller07]

No, definitely something wrong with your map. and your elevation map is all screwed up as well. Check out this example from one of my missions. Ladar 3 Mapping flight
What were your mission parameters (overlap, height, speed, etc.)?This was flown at about 200 ft AGL

Just to clarify you used LADAR as in with a laser?

 

[GVDD scout]

I'm using Map Pilot and Maps Made Easy and did a couple of tests, but I think I am getting much more detail than I really need and that's costing me a lot in points.

If, for example, I wanted to do a 50 acre quarry and be able to accurately determine volumes, what would be a good height and overlap? (for a P4P)

What about an orchard or vineyard?

I noticed that in the rendering some of the structures on the ground look a little funky. Does this happen with other systems as well?

The funky, sometimes mushroom like appearance is the result of camera angle with respect to the sloping surface. Higher overlap will help this, but will generate more images. If I were flying a quarry; 50 acres with 70 ft piles, I would program a grid with 75% overlap on both directions, fly at 250 ft, (gets the drone 180ft over the tallest object you are going to analyze). Understand that I am saying this with no experience with MP or MME, and these recommendations are based on my experience with Pix4D, Drone Harmony and Drone Deploy. Similarly, if you are surveying a vineyard with intent to do any real analysis of the vines and trellises, (vine health or production estimates), you would best program flights up and down the rows at an elevation of about 65 ft AGL, (if the ground is flat), and shoot images with the gimbal at 45-50 degrees down, 80 % overlap for decent keypoint and matching . Pix4D will process oblique data, but again I do not know about MME, and if you are limited to a 'small' number of images per processing. Lastly, numerous and consistently accurate GCP's are your best friend, and they can correct some distortion that is the result of low overlap.

Cheers!