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localdevices / pyorc

Surface velocity, object tracking, and river flow measurements in an open-source API
GNU Affero General Public License v3.0
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Parameter "z_0" #151

Closed MemoGonzalez23 closed 7 months ago

MemoGonzalez23 commented 7 months ago

Hello everyone,

I leave this post to ask some questions about the parameter "z_0".

I am working on some videos that I have stored in my computer. First of all, if I don't have the terrain information, that is, I couldn't measure the water hair in the video I am testing. How do I estimate the value of "z_0"?

Likewise, between what values can "z_0" vary?

Regards

hcwinsemius commented 7 months ago

z_0 is the water level as measured during your survey, measured in the same datum as your control points. This is necessary to be able to interpret the perspective across the water surface. If you only collect one single video, you can measure z_0 with the same instrumentation as used to measure your control points. You can the simply set h_ref to zero when setting up the camera calibration and set h_a also to zero when processing velocimetry to indicate that the water level of the video you are processing is the same as the water level as measured during the survey.

This is further explained in a schematic diagram under https://localdevices.github.io/pyorc/user-guide/camera_config/index.html#example-of-survey-situations

Does this answer your question?

MemoGonzalez23 commented 7 months ago

Yes, thank you very much.