C3D 2019 Image Insertion/Projection Issue
OK, I got it. The issue is the drone imagery, not any ol' imagery, but the composite drone imagery or the 'stitched-together-from-individual-tiles-image. In this composite image, there are gray areas emanating from the corners because they represent areas devoid of tiles, the gray is just fill-in. If you include both the gray areas and the aerial photo, you'll get a rectangular raster. However, if you use a Magic Wand and eliminate the gray and keep only the aerial image, you'll end up with a funky shaped image. Unfortunately Acad doesn't have that Magic Wand (at least I don't think it has a wand) whereas other programs do. Too bad. (There's really no wand. Those other programs can handle funky shapes whereas Acad can't.)
The world file, or tfw, are the instructions that tell your computer program how to position the image, where you see it in your dwg. The instructions involve datum, projection, scaling and rotation. All that combined with a known CS you assign to your modelspace makes the image plop down accurately relative to other real world objects in your dwg. Keep in mind the composite-tfw is associated to the composite-image or the stitched-together-funky-shaped-image-WITHOUT-the-gray.
I don't know a way to inform Acad that the image is a funky shape. AFIK, Acad doesn't support funky shaped images and somehow, amends the funkiness by adding-in gray areas in order to make it rectangular (Acad likes rectangular images). Combine this amended rectangle with the original tfw and you'll get whacky results. Remember, Acad erroneously linked the original tfw with the amended rectangle, not the funky shaped stitched together composite like it should have. Why Acad is capable of linking them like that is beyond me. Afterall, the shape has changed from funky to rectangular but the link still remains. Intuition tells me the link should fail when the shape changes but wutdoIno. Doh?
You have two options:
Option 1, Use original tiles. I'd suggest you back to the original tiles and figure out exactly which ones you need. Each one will have its own individual tfw file. Then use MAPIINSERT to bring in each tile. (Use Shift+click or Alt+click to select multiples.) As long as a tile doesn't have any gray stuff, it's go to go. If you have lots of tiles, this option may be way too cumbersome. Also, with a lot of tiles, they're subject to accidental nudging because they're individual tiles, not a composite image. Warning: since I don't have access to the original tiles, IDK if this will work. It's the path of least resistance and worth a try anyway.
Option 2, Export a new image. Use a geospatially capable program (I used Global Mapper) and export a 'portion' of the composite image. I exported to jpg (I tried Geotiff but spatial placement was still whacky) and made sure to create a jpg world file (.jgw) when during export. To keep the exported image a rectangle, Acad likes rectangles, I drew a bounding box which 'defined the area' of export. I also exported 2 images for better coverage, a top portion and a bottom which abutted one another. Using MAPIINSERT command I accurately placed both images, Yay! Also used Data Connect on same 2 images, making sure to check 'Combine into one layer' on the Data Connect palette. Also edited <unknown> in the CS column to WV83-SF.
One more thing, don't confuse a newly redefined geospatial image exported using Global Mapper with the image clipping function in Acad that you can use to crop an image. Clipping an image in Acad simply means you are hiding portions you don't want shown--it's still the same image with parts that are cropped. Want you need is a new image, with new limits which, in turn, define a new image shape and a new world file to go along with it..
Chicagolooper
