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Author Topic: Orthorectification of photos  (Read 3520 times)

jessica_tay

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Orthorectification of photos
« on: April 28, 2017, 12:53:41 PM »
Hello,

I am wondering if the orthomosaic is already orthorectified? if not, how do I do the orthorectification to reduce distortion?

When I export the tif of the orthomosaic into arcgis, it looks a little tilted. I guess by changing the projection, it helps a bit but is there a way to orthorectify the mosaic?

Thank you!

regards,
Jessica

SAV

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Re: Orthorectification of photos
« Reply #1 on: May 02, 2017, 03:26:27 AM »
Hi Jessica,

If you used ground control points and/or if the pictures you processed were geotagged (which means they include location information), then your orthomosaic will be georeferenced and orthorectified. Don't forget to select GEOGRAPHIC as projection type in the BUILD ORTHOMOSAIC processing step.

Note that you'll have to build a 'high quality DEM' in order to get properly distorted orthophotographs, because the elevation information of the DEM is needed to remove the distortion from the images.

Also make sure that you use the same coordinate system during export from Photoscan and import in your GIS software package. Simply check if the EPSG codes are matching.

Regards
SAV

Jeremiah_ROWE

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Re: Orthorectification of photos
« Reply #2 on: May 02, 2017, 04:41:30 PM »
I agree with SAV.

Another point to consider is the images themselves. Depending on which direction your photos are taken from, Agisoft may only have images of a certain perspective to incorporate into the data.

If there is a particular portion of your ortho that you'd like to investigate for improvement simply draw a polygon shape on the ortho over the area of interest and then select it followed by a right click, choose Assign Images. You can filter through the different image file sections that Agisoft can use to fill the area within your drawn shape.