Photogrammetry
Oct 22, 2022 11:44:03 #
Dikdik
Loc: Winnipeg, Canada
I've been involved with a couple of mining projects where they have used drones with LIDAR to generate a drawing of the interior and also a couple of electrical facilities.
Oct 22, 2022 14:24:36 #
jerryc41 wrote:
Do any of you know anything about photogrammetry? I've been watching shows about exploring tombs from ancient Egypt, and they used that technique with DSLRs and software. From what I've seen online, it involves complicated, expensive equipment.
If you know a local forester ask him for help We take a lot of phoyogrammerty in school and most of use aerial phorp daily
Oct 22, 2022 14:40:12 #
wmysd
Loc: California
My dad retired as chief of photogrammetry at a nearby county, and my mother retired from, and then sold, a business named Analytical Photogrammetric Surveys, and I still don't know what they did or how, except at the end of the day there was a map.
Oct 22, 2022 14:40:54 #
Remember the Hasselblad Photos from the Moon, how you could see the little + grid marks across the frame?
Those came from an optical glass reticle at the film plane, called a 'Reseau" Plate.
The principle being if you know the precise distances of the + marks and the precise focal length of the lens in use,(and probably focus setting if not infinity),....
You can use those to interpolate the sizes if things in the frame. So you have a photograph, and a measuring device.
That is one way to do it. More modern digital systems use software and fixed focus lenses to do it in basically real time.
Those came from an optical glass reticle at the film plane, called a 'Reseau" Plate.
The principle being if you know the precise distances of the + marks and the precise focal length of the lens in use,(and probably focus setting if not infinity),....
You can use those to interpolate the sizes if things in the frame. So you have a photograph, and a measuring device.
That is one way to do it. More modern digital systems use software and fixed focus lenses to do it in basically real time.
Oct 22, 2022 16:30:51 #
Crime scene investigators will use "total stations" or a variant of that to map crime scenes and draw detailed maps. The technology is also used in one form or another for real estate walk-through videos and is no more difficult than repositioning a tripod mounted unit and getting out of the picture. I have seen these units go for less than $5k and B&H carries them.
Oct 22, 2022 16:36:58 #
Dikdik
Loc: Winnipeg, Canada
...and I don't know why they aren't using LIDAR. It can 'create' a very accurate 3D 'scene'. The accuracy is adequate to be used for surveying on large projects. Drones can be used for this purpose.
Oct 22, 2022 18:04:41 #
I have a son who works for an aerial photogrammetry company. They have worked on mapping projects for National Geographic, Apple, Google, the US and foreign governments, private industry, etc. It’s amazing what can be determined by photogrammetry by plane and satlittle imaging. Not only leniar measurments, by volumes, stock piles, etc, and 3D imaging.
Oct 22, 2022 23:04:37 #
Wyantry
Loc: SW Colorado
jerryc41 wrote:
Do any of you know anything about photogrammetry? I've been watching shows about exploring tombs from ancient Egypt, and they used that technique with DSLRs and software. From what I've seen online, it involves complicated, expensive equipment.
Expensive equipment not necessarily required!
For Forensic photogrammetry, a target-set (two or more) of a known size may be placed a known distance apart at right-angles to the plane and on the centerline orientation of the camera. When photographed, then printed or analyzed on a computer, an investigator can determine angles, distance and orientation by measuring and comparing apparent axis length (two axes at 90 deg. and trigonometric calculations. This will allow distance and anglular determinations.
~~~~~
REFERENCE SOURCE: https://www.crime-scene-investigator.net/photogrammetry-simplified.html
” Photogrammetry Simplified
Bob McMicken; Copyright ©2016
“Photogrammetry is the science of making measurements from photographs. That definition comes from http://www.photogrammetry.com where you will find links to other photogrammetry sites. Photogrammetry.com classifies photogrammetry as:
— Aerial, which is used for terrain-mapping from an aircraft.
— Close range, which is used for archeological, architectural, engineering and forensic purposes.
Our interest in this tutorial is limited to basic forensic photogrammetry using standard digital cameras and entry level photo editors. I'm indebted to Larry Barksdale for his Irfanview Photogrammetry PowerPoint and to George Reis for Chapters 15 and 16 in his excellent book Photoshop CS3 for Forensics Professionals, available as an e-book from http://www.wiley.com. . . .”
~~~~~
Currently, I am working on a project for soil and geologic formation identification. For this I use two 10 cm targets placed perpendicular to the camera plane, spaced horizontally two (2) meters apart (or more for large-scale outcrops or areas). This gives both a scaled target and a known baseline for calculations.
Oct 23, 2022 07:57:44 #
spencehg1 wrote:
Check out https://sketchfab.com/FOFSedona br We do... (show quote)
Yes, that's it. Thanks.
Oct 23, 2022 14:49:06 #
Jersey guy
Loc: New Joisey
I live in the middle of where George Washington and his troops encamped in the winter of 1778-79...the Middlebrook Encampment. In my own community we have the sole remaining evidence of what had been 3 fortifications called "Redoubts". I worked with an Historian/Archealogist and a man from Hunter Research who had a Drone with LIDAR capabilities. The Redoubt in question has been part of our common property (a homeowners assoc.) since its inception in 1946 and was preserved by the farmers who owned the area since Revolutionary times. On the ground it looks like an irregular, overgrown area but the LIDAR scan showed an amazingly perfect geometric parallelogram shape. LIDAR can detect variations in the ground of a few inches that one would never notice walking the same area.
Oct 23, 2022 16:11:25 #
Dikdik
Loc: Winnipeg, Canada
I think the point cloud that LIDAR produces is far more accurate than photogrammetry means, and is a lot less costly.
Oct 24, 2022 09:26:50 #
Jersey guy wrote:
I live in the middle of where George Washington an... (show quote)
Yes, LIDAR is amazing. It's been used in South America to find ancient structures.
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