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Photogrammetry

jgarnold

jgarnold

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australia
Could someone please explain how photogrammetry works. I could not obtain an answer to this question in the SDK documentation (or I didn't scroll down far enough).

It seems from personal observation that apart from the display of the surface (satellite imagery) it also contains some ground elevation.

In one particular (world) location when it is OFF it displays, generally speaking, how the terrain of that area of the world appears today, but when it is ON it overlays the area with how it appeared a few years ago with a different (ground) elevations/small hills.

Thanks
 
Photogrammetry is the science of converting images into 3d. Some algorithms use the colors of the images only, Google photogrammetry uses LIDAR, which basically works out like a super intense flashbulb from the satellite. It take a photo and also gets a height map.
 
Thanks Rick. I always thought that it only resulted in 'improved buildings' ie 3d buildings only. Pity exclude TIN has no effect on height as terraforming can be a challenge.
 
Triangular Irregular Network is not photogrammetry and is generally specific to non terrain items. I have seen TIN trees in Google Earth and TIN outcroppings are conceivable. MSFS TIN seems fairly sedate.
 
In simple words, photogrammetry is a complex technique that uses images from different angles of an object to build a 3D model and apply the images as textures.

For a simple object, you can take the images with any camera and use software that does the process.

For a city (like those of MSFS) satellite photos and aerial photos (with drones, or helicopters) with special cameras that store geoposition information (GNSS?) are required.

It's definitely not something that can be done with the Sim's tools.
 
Thanks for the explanation. It seems to me IMHO that scenery from Bing and scenery from Photogrammetry was taken maybe years apart which is a pity as they often conflict.
Consider the following two images from MSFS, the first one with photogrammetry OFF which shows the area much the real area currently appears (ie the new road approaches and no hill) , and the second with photogrammetry ON which shows the old approach roads and a hill). The new approach roads have existed since 2018 (when the new bridge was opened). Pity they both aren't from about the same time.
Or am I not understanding this correctly?
VICTORIA_OFF.jpg


VICTORIA_ON.jpg
 
Absolutely, photogrammetry is generated from aerial photos (drones, helicopters, planes) not from satellites, that is why we do not have photogrammetry of the entire planet, only of the big cities where someone has taken the trouble to take aerial photos with geolocation .
Then MSFS uses both to present the scenario, but it would be normal for both photos to have been obtained at different times.
 
Ah see I'd been of the belief photogrammetry was also obtained by satellites and triangulation was obtained by positioning. Years ago, about a decade actually, Google was just starting to populate Google Earth with mesh and they turned to the community to accomplish this, although it seems likely they hired professionals to do the major landmarks. They published a software called "Building Maker" and it had access to satellite imagery. The idea was that in areas covered by two or more satellites, the offset of the captures served as the triangulation. All one had to do was find an area of coverage, as in most of America, Europe and many major urban areas worldwide. Then you'd zoom into a single building, trace it's outline and click to process. Voila, there would be your house on your desktop. Really the software only needed a footprint, the user supplied the vertical dimensions and any available imagery would be mapped to the faces. Very fun stuff, of course they shelved it all after we'd taught the algorithms how to do it cheaper..?
 
Thanks degorap. Is it private or professional's photos which are used and how often 'they' update their aerial photos as the area I showed above obviously was 'taken' during or before 2018.
 
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