An orthophoto, orthophotograph or orthoimage is an aerial photograph, geometrically corrected (“orthorectified”) such that the scale is uniform (Wikipedia)
ArcMap can be used to orto rectify aerial images to a NAIP imagery as a basemap.
I usually ortho rectify thermal imagery using this method, as we don’t have orientation information for the acquired thermal images.
These are the steps that I follow for creating ortho-mosaic from thermal imagery:-
- Extract tiffs (32 bit) tiffs from the raw sequence file recorded by FLIR SC640 thermal camera.
- Convert 32bit floating tiffs to 16 bit unsigned integer format, as later I will use the rectified tiffs in PhotoMod for fine adjustments.
- Perform batch lens distortion correction on each frame.
- First download the desired base-map (NAIP Ortho imagery) from Geo Spatial Data Gateway or if I have a high resolution and more recent ortho-mosaic I can use that too.
- In case you have downloaded multiple tiles to cover the area of interest, you might want to mosaic the tiles together. I have discovered a quick way to mosaic tiles using gdal.
- Open the basemap (NAIP) image in ArcMap.
- Add a thermal image (one we corrected for lens distortion and converted to 16 bit) in ArcMap and
- Make sure Georeferencing toolbar is enabled, else enable it from customize&gt;&gt;toolbar menu.
- Watch the following video for detailed steps to create tie points and rectify image.[spacer height=”20px”]