Drone Photogrammetry: How drone photos turn into 3D surveys - COPTRZ
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Drone Photogrammetry: How drone photos turn into 3D surveys

Hayley

12:21 pm GMT •

August 21, 2018

Using drones to create 3D surveys of your land is an incredibly powerful tool to have. By simply flying your drone above the land, you are all of a sudden left with a highly in-depth 3D model of the terrain, allowing you to make incredibly accurate commercial decisions. Well, if you’re wondering how all of this works, you need to first understand the basics of drone photogrammetry.

What is photogrammetry?

Simply put, the art of photogrammetry is to do with using photos to measure something. When you fly your drone over the required terrain, the camera takes an incredibly large number of shots. Most of which overlap each other by about 80%. This allows the drone to gather an almost complete 2D, and to some degree 3D overview of the land below it.

After you do this, you need to fly your drone closer to individual features that are important to your final model. The more shots you can get from each feature the better, as this will later give your chosen software a greater ability to calculate things like depth. This will allow your finished 3D surveys to be as accurate and valuable as possible.

Later, these images can be stitched together in order to create the final 3D rendering you see on screen. It is for this reason that you are required to fly your drone slowly and with complete steadiness. Otherwise, you will fail to gather enough necessary shots to put together an accurate and detailed 3D model.

The power of Pix4D

For highly accurate 3D surveys, we recommend using software like Pix4D to piece everything together for you. The software takes all of the photos from your drone and grinds them down into millions of pixels. The software is then so powerful that it is able to take all of these pixels and reconstruct them into a 3D picture.

Bear in mind that Pix4D will only have access to the information you feed into it. So you need to give it plenty of data to work with. It will require you to first input all the 2D shots from above. It then aligns these perfectly, based upon the coordinates of each individual shot. This initial process is known as gathering an orthomosaic overview of the land.

Purely from these shots alone, the software will be capable of creating some 3D modelling, however, its accuracy will be very limited. To then give the software access to things like depth, you need to provide different angle shots of the various objects and key points of the landscape. This is when it’s time to get a bit closer to everything.

Stitching things together

In order to combine all of these shots together, the software uses a technique called stitching. This is where it identifies key points, shapes and colours in order to identify where something belongs. Think of it as an incredibly complex jigsaw puzzle, where each jigsaw looks almost indistinguishable to the human eye.

Well, software like Pix4D is able to identify what it needs and stitch them together in a matter of minutes, or hours, depending on the size of the area you are mapping. Of course, the software cannot perform miracles. If large areas offer no significant features or fluctuations in elevation, then it will struggle to put together an accurate model. This is why it is so important to get a wide variety of shots, not just from above, but also from closer up and from lower altitudes.

Putting things into perspective

The best way to better understand the basics of photogrammetry is to use an example. And in this case, that example will be your eyes. Take a look around the room you are in right now. Why is it that you are able to measure the depth of everything around you so quickly? Well, it’s because you already have your own Pix4D software programmed into your brain!

To start with, think of your eyes as two cameras. All they can do is take 2D shots of the room. They do this from 2 different angles and are essentially taking thousands of individual shots every microsecond. Your brain is then processing these images almost instantaneously, piecing them together into 3D models, and then transferring these finished models back to you.

So instead of seeing a 2D world, you get a continual 3D look at your surroundings. And this is only possible because you have each eye continually taking shots of the room from different angles and measuring things like distances, in order to give you a sense of depth and perspective. Drones are like your eyes, and the Pix4D software is like your brain.

 

The key to success with photogrammetry

If you are looking to put together detailed 3D surveys of your land, then there are no shortcuts with equipment. In order to get truly accurate and valuable finished models, you will need the right tools for the job. For this, we highly recommend the DJI range, combined with Pix4D software.

The exact drone you go for will depend on the landscape you are trying to map and the experience you have flying commercial drones. Well, luckily for you, COPTRZ are experts at 3D mapping. We have helped numerous businesses across the UK to incorporate the right drone and software solution for their needs. We also help with all the necessary training on how to correctly carry out 3D surveying. To find out more, simply get in contact today.

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