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Distortion of Images when processed

I have just had two maps processed.  Both of school roofs.

Both processed ok for about 90% of the roof, where the roofing material is felt or single ply membrane of some sort.  But both schools had a  small part of the roof of profiled metal sheeting.  In both processed images this part of the image is distorted with no continuity of the steel sheet profile lines - they are all over the place at random

What is causing this?

 

Desmond Yates

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Please refer to our support article that is specifically about roofs:

Your Overlap Reports show that you had decent overlap but there are always going to be issues with corrugated metal roofing and direct reflective sun. White reflective repeating patterns are bad... (noted in the Data Collection guidelines that are agreed to at the time of upload)

Note that only the directly sunny part of the roof is having issues. You may need to collect your data during periods of overcast or indirect light.

Zane
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Thanks that is useful info. The weather is out of my control unfortunately as these surveys are all prearranged but I have  more to do. I am flying at 50m with a Mavic 2 Zoom on full zoom, flying using Litchi.   Looking forward could I take a few individual shots of corrugated roofs from a much lower level after the general mapping flight and add those to the data to reduce any overlap issues?  Will the processing take account of the height of the drone?  Or would it be better to go higher?  

Desmond Yates 0 votes
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I wouldn't mix the elevations of your images like that. If the images are taken at a different time the lighting conditions are bound to be different and cause feature matching issues. All data is to be collected at the same time to get the most uniform lighting possible. 

Use a circular polarizing filter to cut down on back reflections. If you really care about the quality of the reconstruction of the roof you will need to make sure your camera exposure is set properly for that specific area. If it is blown out due to overexposure there will always be spikes in the DEM and discontinuities in the model. 

Zane 0 votes
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