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Drones Could 3D-Map Scores of Hectares of Land In Just a Few Hours
sciencehabit writes: Unmanned drones aren't just for warfare. In recent years, they've been used to map wildlife and monitor crop growth. But current software can't always handle the vast volume of images they gather. Now, researchers have developed an algorithm that will allow drones to 3D-map scores of hectares of land in less than a day — an advance that is important for cost-effective farming, disaster relief, and surveillance operations.
Their computer program directly projects the points from each photo onto a 3D space without knowing the exact shape of the land or the camera positions. As a result, the tie points don't necessarily match up, which means the same corn plant can have two projections on the model. When that happens, the algorithm automatically takes the middle point between the two projections as the more accurate location and adjusts the camera position accordingly, one image at a time. Because the algorithm tweaks far fewer things at each step, the shortcut drastically speeds up calculations. Once the software has adjusted the camera positions for all the photos, the software repeats the entire process — starting from projecting the points to the 3D space — to correct for any errors.
Their computer program directly projects the points from each photo onto a 3D space without knowing the exact shape of the land or the camera positions. As a result, the tie points don't necessarily match up, which means the same corn plant can have two projections on the model. When that happens, the algorithm automatically takes the middle point between the two projections as the more accurate location and adjusts the camera position accordingly, one image at a time. Because the algorithm tweaks far fewer things at each step, the shortcut drastically speeds up calculations. Once the software has adjusted the camera positions for all the photos, the software repeats the entire process — starting from projecting the points to the 3D space — to correct for any errors.
Depending on the accuracy obtained, such mapping would be highly useful on our farm for figuring out drainage. Some areas of a field might drain better with only a very small slope, if we knew where to put the channel. Currently the only real option is to drive over the field with an RTK GPS receiver and make a GIS map of elevations. Which works well enough (depending on the grid resolution; can get really old driving every 10 feet over 160 acres), but takes quite a long time to do.
TFA states that the old algorithm breaks down once the number of source images exceeds a few hundred, at which point it can take thousands of hours to process. The new algorithm can accommodate over a thousand images and process them all in about four hours.
John