0

I'm trying to figure out what coordinate system and projection to use to get these raster aerial photos to work in ArcGIS Pro. They are old NHAP aerials downloaded from Earth Explorer. I don't see any relevant information that might help me. I've tried many different coordinate systems with Define Projection. Projected coordinate system seems to get close, but otherwise it ends up in the ocean. This is what the info looks like.

enter image description here Edited to add: enter image description here

mapster2000
  • 1
  • 2
  • Can you link to them so we can download? Maybe they don't have a coordinate system and you'll have to manually geo-reference them? – Spacedman Oct 14 '22 at 13:40
  • If the image is 10700x10574, then those are just center-center pixel location values, and the image is probably not georeferenced at all... – Vince Oct 14 '22 at 15:49
  • It is from the USGS Earth Explorer. https://earthexplorer.usgs.gov/. The images are from 1984. I don't see anything in the metadata about coordinate system. https://www.usgs.gov/centers/eros/science/usgs-eros-archive-aerial-photography-national-high-altitude-photography-nhap – mapster2000 Oct 14 '22 at 15:50
  • It has all of this information in the metadata (added above to question.) Can that be put in manually? – mapster2000 Oct 14 '22 at 16:03
  • I'm trying to work out where those corner points exactly go. There are four cross-hairs on the image that are likely to be those coordinates, and my first go with the GeoReferencer has failed because I think the image is East-up. Trying again... Unless every image has the crosshairs in exactly the same place you'll have to do it manually.. – Spacedman Oct 14 '22 at 19:22

1 Answers1

0

I don't know how ArcGIS Pro can georeference images but this is done in QGIS and a similar workflow must exist in the ESRI world.

Load image into the GeoReferencer.

Zoom in and click on each corner target point. Enter that point's coordinates, noting that if the image is East-up then NE is top left, SE is top right, NW is lower left, SW is lower right.

enter image description here

Do all four target points. End up with something like this - four red dots and a table of four source and destination coordinates:

enter image description here

Set transformation settings to type: "Projective" and Target CRS to EPSG4326 lat-long. Hit OK and hope...

For the one I tried, NB1NHAP020524079.tif I got this (superimposed on b/w contemporary satellite imagery):

enter image description here

Its ball-park correct but there are alignment errors with the base layer - these could be because of various reasons - the lat-long given isn't WGS84 or accurate enough, or distortions in the photographic process (are these oblique?), or possibly the lat-long corners arent the cross-hairs, or possibly the transformation is wrong.

If you can find enough point features in the image that are visible on other basemap imagery you can tell the georeferencer to match those points and warp or otherwise stretch the image to fit those coordinates. This can be used to get round errors such as the above. Just make sure your features haven't moved since the image was taken...

Spacedman
  • 63,755
  • 5
  • 81
  • 115