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Maximum images for processing and minimum overlap for weed identification

I've been asked to produce maps of properties 200-500HA in size at 2cm/px resolution. It looks like this will generate 7000+ images.

1. Is the processing limit still 4,000 images?

2. MapPilot generates flights with a very slow speed of 2.5m/s which would mean flight times over 9 hours. If I plan the same maps with DJI's GSPro it sets a speed much higher around 10m/s which of course really cuts down the flight time. Is it OK to generate my maps with GSPro but process them with MapsMadeEasy? I've been a customer for a long time and really want to continue using only your map processing if at all possible.

3. What's the lowest overlap suitable for weed identification? I was planning on 80 forward and 70 sidelap. If it can be done with less that would be good of course. But I do want the highest quality for my client.

Thanks.

Darrell

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1. 

2. You can set the speed to whatever you want but the camera is physically limited to only be able to take 1 image every 2 seconds. Depending on your flight height, overlap, and camera focal length the camera is what is setting your max flight speed. We don't generally recommend using GSPro because it lets you do so many things wrong. As with anything, do some small trials first so you really understand what is going on before doing a huge data collection effort. You should break that area up into 50 hect sections. The forward overlap value is what is slowing things down. We would recommend using 75/75 for this type of mission but you could use 70/80 which would speed up the flight a bit. 

3. Overlap is one thing. Generally the more the better. But for weed identification GSD is likely going to be more of the deciding factor. The more pixels you have on target the easier it will be to make determinations. This means flying lower or using a narrower field of view camera. The real answer is testing testing testing.

Zane
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1. You can break up the project into sections and either merge them in QGIS or use MME's "Locations" feature to display them together.

2.  The closer you fly to the surface, the slower the drone must go in order to have motion blur be lower than GSD.  Map Pilot takes this into account.  I do not know if GSP does, but 10 m/s for 2cm GSD is extremely optimistic.

Images can be captured by using any control app, but good processing results depend on good sharp imagery.

3. The more homogeneous the surface, the more overlap.  If the weeds are thick then your plan would be the minimum.  If sparse, then you might be able to open it up a little.  I would stick with what you have. If it's like a sea of green, you may need more overlap.  If at all possible, why not do a small sample that you can process for free and use the results to guide the project?

Dave Pitman 0 votes
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It also depends on the drone. We did some testing with a DJI Phantom 4 and a DJI Phantom 4 Pro. The camera on the Pro made the ability to fly faster at lower altitudes possible. The Pro has a rolling shutter and less blur and allows one to adjust the fstop. From Forbes "The Phantom 4 Pro is another clear winner here. It offers a superior 20-megapixel shooter and its ISO range is an impressive 100 to 12800. It offers burst shooting with 14 images at a time (compared to 7 for the Phantom 4), along with all the other modes you’d want." There are some things that are easier in GSP and Some things that are easier in MapPilot. Map Pilot has some features that DJI doesn't. I have used them both. Your mileage may vary. I do know that to identify weeds. etc. you will want to change the fstop to at least f11. I did a somewhat similar project and we did a bunch of test flights with DJI Go just to see what fstop worked best before doing an automated image stitch. I totally agree with testing, testing, testing. 

MSquared 0 votes
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