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Author Topic: Area and volume measurements - best solutions?  (Read 6885 times)

Dagon

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Area and volume measurements - best solutions?
« on: May 10, 2017, 11:18:43 PM »
The instructions in the Photoscan manual for obtaining area measurements seems to only provide a total area for the entire map. Same for volume. Is there a way to define outlines in Photoscan and get the area measurement of just that portion?

If not, what is the best way to do this? Does a geotiff contain this information? How best to export and query it?

Otherwise, can someone recommend simple software that will allow me to extract distance and area (and possibly volume) data from Photoscan output files?  Preferably something cheap/free and intuitive enough that students with no GIS knowledge can use without too much of a learning curve.

Here's what I need to do: I will be using Agisoft to make extensive UAV maps of ruins in Peru and then working with undergrad students to extract and analyze information from those maps, so I will need to set up several workstations where students can make and record distance and area measurements (room/courtyard area, wall length, road widths, etc.)

DroneDeploy does this in a very simple, straight-forward way but I would hate to have to pay the full subscription price for each workstation just to use measurement functions. I'm sure there are good standalone options but there is so much stuff out there that I'm having trouble figuring out what will specifically fit my needs without too much overkill.

Some help with this would be very much appreciated. I'm the drone guy who was tasked with solving this problem but my GIS knowledge is woefully inadequate.

Thanks!

SAV

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Re: Area and volume measurements - best solutions?
« Reply #1 on: May 11, 2017, 04:17:29 AM »
Hi Dagon,

Yes, it is possible to measure the volume and/or area of just a portion of the map in PhotoScan.

Open your orthomosaic or DEM. Then click on the DRAW POLYGON icon in the main (top) toolbar (it has the shape of a pentagon). Next, digitise around the object you want to measure. Double click to close the polygon. Then right click on the digitised line and choose MEASURE. This will then show you the volume and area as well as a profile of the digitised line.

Alternatively, you could also use CloudCompare (www.cloudcompare.org which is free and open source to compute the volume of a certain region. This is how you would do it: http://www.cloudcompare.org/doc/wiki/index.php?title=2.5D_Volume
Btw, CloudCompare might me useful to do some other analysis for your studies.

Sounds like some really interesting work you are doing in Peru (love that country).

DroneDeploy is quite expensive (if you use it frequently) and does not really give you much control over the photogrammetric processing. You are much better off using Agisoft Photoscan Pro instead; the educational license is quite cheap.
In case you are using one of the (newer) DJI drones such as the Phantom 4/Phantom 4 Pro or Phantom 3 Advanced, I highly recommend to use either MapPilot or DJI GS Pro to plan your aerial surveys (both only run on iOS devices though). It makes image acquisition really easy.

All the best for your work.

Regards
SAV

Dagon

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Re: Area and volume measurements - best solutions?
« Reply #2 on: May 11, 2017, 07:20:00 AM »
Thanks, SAV. I really appreciate the feedback.

Yes, we're using a Phantom 4 Pro and a Phantom 3 Advanced. I'm very pleased with the results I'm getting with the Agisoft trial and we will definitely be getting a couple of educational licenses. I have heard good things about  MapPilot and DJI GS Pro but we are using Android tablets. I have found Pix4D's mission app (which is free from the Playstore, even thought their processing software is very expensive) to be quite robust, apart from not being able to consistently recall satellite imagery in the field for tweaking missions on the fly.

I will check out CloudCompare, but it sounds like Photoscan will meet our needs.