New to ODM 12/26/21

Real Estate Photographer, intermediate drone pilot, have Part 107, understand the capture process, have run practice missions many times with my Autel Evo II 8k drone. This ODM is daunting to me. Looking for step by step instructions on how to get up and running.

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Welcome!

There’s a lot to any tool, as you know, so let’s start with basics:

What operating system are you planning on using? What are the specifications of the machine you’re planning on processing on? What are your projected mission sizes (image count) and output product quality (GSD or otherwise) metrics?

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I am using an iMac. I have already checked the specifications and my computer is fine. I have no idea what projected mission sizes will be, I’m just starting out, so I have no clients. Output product quality? GSD? I don’t know what those mean. I have already run a couple of test projects and I’m getting decent results, I guess. I did an orthomosaic and it looks pretty good.

GSD- Ground sampling distance is what the width of a pixel represents in reality. So the hight of your flight, sensor and focal length determines the GSD.

I like to have a front overlap of 80% and 70% at the side. You should also fly a bit outside the area you like to cover.

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Thanks, Andreas. I appreciate it. I usually fly between 125 and 150 feet altitude, and my overlaps are pretty much the same as yours. I have a flying question: When I’m flying, the maps are not current so I can’t very accurately draw out my mission. I know some map companies let you pre-plan your mission on your computer, then upload it to your device. I think Drone Deploy has that. But I think you have to pay for their services in order to pre-plan. My Autel Evo II has a built-in mission function that works great. But the map is terrible.

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If you’re mostly surveying properties, you should be able to get up to date GIS data of parcels/tax boundaries from your local municipality. Some will also offer more up to date imagery you can use. Depending upon your flight planning tool, you may be able to make boundaries in a GIS program like QGIS (based upon data from your municipality) to export to your flight planner.
Some other flight planners like Mission Planner allow you to use custom basemap raster data (GeoTIFFs) directly, which can also be handy. I’m not certain if the Autel flight stack is PX4/ArduPilot compatible and can be used with something like that, so you’d have to check with their support. They may even have a method for their own planner to use custom imagery.

If you’re looking to mainly do 3D Models, try to keep overlap/sidelap at 85% or higher to make it easier on yourself.

Stephen also has a great blog series on flight plan design and parameters that can greatly improve your results:

For getting a bit more information on OpenDroneMap and how to use it, you can check out our documentation:
https://docs.opendronemap.org

Piero also offers the OpenDroneMap: The Missing Guide book which goes into a lot of detail about the various parameters and concepts.
https://odmbook.com/

As for GSD, Andreas helped explain it. But basically, the spatial or on-ground resolution of each pixel in your image. If you have a 12MP sensor like a GoPro Hero4 Black, at around 400ft GSD, you have roughtly 4.33cm per pixel resolution. Some clients may have expectations for how “fine” they want their output products, so you’ll need to be aware of that when planning and processing. Most flight planners will tell you the GSD estimate when you set up the flight.

Output product quality ties into the GSD. For instance, if you collect at a GSD of 4.33cm/px, you can’t then set up a finer --orthophoto-resolution and --dem-resolution of say 1.0cm/px and get meaningful data, you’re just upsampling/interpolating.

However, if your clients don’t need anything finer than say 8cm/px, you could for instance collect at 400ft GSD (which makes it much faster to collect data for a given area, and makes getting good tiepoints/reconstruction very easy) and then downsample from 4.33cm/px to 8.0cm/px and get very nice data with a lower processing load (CPU time, RAM, storage usage), and it should look sharper and more pleasing as downsampling typically improves perceived image quality.

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Great. Thanks for all the information.

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I use Pix4D Capture or Good station on iPhone to control the flight. They have different maps to help and it’s free.

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Cool. Thanks! I’ll look at it.

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