I’m creating a map of an irregularly shaped piece of real estate that is ~100 acres. It is raw land with some clearings and some tree canopy. At its lowest, it runs along a river (for ~1 mile) and has some rolling hills as you go away from the river. There is a home on it, but I’m not really concerned with that (client will be tearing it down).
The goal is a preliminary survey that allows for some measurement of: acreage of specific areas; elevation changes / grade of other areas; and general, misc measurements. It will also be nice to have a good, detailed map of the land.
As the title of the thread suggests, I’m wondering which of the two settings will produce the better map:
Enhanced 3d Crosshatch @ 70%/60% @ 320’
or
Regular @ 72%/72% @ 250’
Or, if neither of those is ideal, happy to take any suggestions.
Are you trying to get real world elevations with GCP’s or just for relative site slope analysis? I wouldn’t use GCP’s with oblique images. Especially if there are trees and such because you will get allot of distortion of the target and probably will not get enough views with an oblique perspective.
I assume you chose this limits because of battery? Of course you can, but I wouldn’t recommend flying any higher than 250ft. If you just want relative contours then crosshatch would be fine maybe at 250ft and 65/65 overlaps. If you want GCP’s then run nadir at 250ft and 75/65 overlaps. My default is 80/65, but I do go down as far as 70/65 if the scenario fits. Better yet would be running two nadir perpendicular to each other. Because the image ratio is a little wider than tall you get more perspective on the sides and running two directions will help a little under the trees. With a dual path you could run 65/65 on each.
It may be up to 500 feet of variance in multiple spots. And I do not need actual elevations, just relative.
And yes, batteries are the concern. I have 4, and the two plans presented both require 4.
With that said, will cross hatch at a lower overlap be smarter than disabling enhanced 3D and operating at a higher overlap (with no perimeter video)? Would it make sense to add any specific kind of pics after the mapping flight?
Ooh, that’s allot of relief! Tha tis probably going to be best flown with Terrain Awareness which only works on the standard nadir lawnmower pattern. Or depending upon how split up the +/- elevations are you could do two flights. Without GCP’s though this could cause a problem stitching the split. See if terrain awareness is available on the site and I think that would be your best bet. Do you have a KML boundary you could share? I’d like to put it in a flight plan on my end.
I just checked terrain awareness, and it is showing very different numbers than client passed along. It’s showing a low of 250’ and a hight of 480’, with 7 peaks at that height.
The address of the property is 1251 Butterworth Road / Kingston Springs, TN / 37082.
Here is a screenshot of the map plan at 72%/72% @ 250’:
I always look for the direction that I get the most long lines. The concern with the direction you had is that the ends of the west line are so narrower that they are pressed to get two good lanes, but also it was causing you to overfly a pretty good chunk of land. When I had mine at that approximate rotation I also had more flight time. I did bump the altitude up 5ft but small tweaks like that or percentage points in overlap can make a big difference to battery efficiency. The one factor I didn’t take into account is approximating where your takeoff location would be and where battery swaps would need to happen. If you can get 17min of flight time you can do this in 3 batteries, but that will depend on the weather.
I ended up having go to the site four times and do four different flight plans. Each of the first three left large holes in the map. For each, I increased the elevation 50 feet. At 400 feet, I finally got a usable map.
I have one last question, after uploading the pics, I chose Terrain (2d) mode as opposed to Structures. The Map Processing Report says I should have used Structures (3d) mode. First, given that I was mapping 100 acres of terrain (there is a very small house on the land, but I’m not interested in it), why would it recommend I use Structures mode? Second, if it is better, is there a way to reprocess the images and create a new map?
The import process detects from the image exit data. I have seen some trouble with this as well. I don’t know what the threshold is that it kicks over on. I have seen some images have a 0.2 degree variance when they should have been 90, but that shouldn’t be enough. Were there any obliques at all. Even one?
I did a flight with a brand new and freshly calibrated P4P V2.0 and the engine auto-set my mission for Structure processing when all the images are nadir. @Jamespipe@Andrew_Fraser
I checked the EXIF data and there were a couple of photos recorded at an 89.90degree gimbal pitch. That doesn’t seem like it should be outside of a tolerance.
