Photo measuring

General discussions of measurement techniques and the results of testing of techniques and equipment.

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#11)  Re: Photo measuring

Postby dbhguru » Wed Jan 17, 2018 4:43 pm

Ents,

  Please find attached another test of the photo measuring method. The reference object is a 12-inch segment of a yardstick on the other side of my basement room. The target is a whole yardstick. The reference object is oriented close to 90 degrees to the line of sight. The target is oblique to the line of sight, closer than the reference object, and at the left side of the image. As you can see, the measurement error is only 0.514 inches or 1.43%. I'll take it.

 If anyone wants to use this workbook for their own test, first unprotect the photo worksheet. Delete the photo, beige rectangular area, and the blue and yellow line objects. Lastly, delete the contents of the green cells. You're ready to do a new test. Just follow the instructions. If you need more instruction, let me know.

Bob
Attachments
Oblique Photo Measurements 13 .xlsx
(3.53 MiB) Downloaded 4 times
Robert T. Leverett
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Co-founder and President
Friends of Mohawk Trail State Forest
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#12)  Re: Photo measuring

Postby dbhguru » Sat Jan 27, 2018 4:07 pm

Ents,

 With warmer weather, I did a test outside this afternoon of the photo measurement method. I'll spare everyone another Excel workbook, and just report that the measurement errors on the targets  were as follows in inches.

0.847658294
0.583353056
0.347799113
0.585533019
0.172977198
1.197645905

  These results are consistent with past tests. Errors rarely exceed an inch. In this test, the average error over the six trials was 0.6 inches. When you think about it, that is darn good. The method continues to exceed the accuracies I initially expected. The method appears to have a future.

Bob
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#13)  Re: Photo measuring

Postby Don » Tue Jan 30, 2018 12:14 am

Those in the Cadre that are following Bob's "photogrammetry" exercise this far, should check in at the Cadre Forum.

Stuff's happening there, that I'd think you'd want to weigh in on...
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