Help inserting orthophotos into autocad for digitizing

[Jeff007]

I am trying to insert a digital orthophoto (.tif) into AutoCAD 2000, but the image is not at the proper scale. I do have a world file (.tfw) but I'm not sure what the proper use of this file is. Any help would be appreciated...

 

[carlorom]

Hi,
This is quite a tricky operation as it depends what you want to use the photo for. I can't give you specifics but the basic concept is to match your world co-ordinate file to the orthophoto. I would imagine it will also involve a user co-ordinate system operation in ACAD. You will need quite a number of known points to get a proper match with scaling etc as there are always distortionsin such photos. Litterature on Photogrammetry will help to illustrate this problem. I know there are various software packages wchich will do what you want (a lot of Geographic Information Packages will offer this) BUT BE CAREFUL ABOUT DISTORTIONS. This is a specialised field best left to Photogrammetrists to sort out. I therefore feel it would be useful to cantact your nearest survey / geomatics teaching institution for specific help.

 

[bundle]

hi...
generally after producing orthophotos we register them to their real coordinates, and you can see that information in the begining of the TIFF file. if you view it as ASCII (header information). if you can't see those real coordinates in the header information that means the orthophoto wasn't registered. in that case i am sorry for your orthophoto. you need to contact with your producer. first you should check those coordinates.

OR

if you have the corner coordinates of orthophoto you can register it by yourself.

good luck...

 

[AllenS]

If you are going to be doing a lot of this now and in the future I would recommend purchasing CadOverlay form Autodesk. It will not only automate the insertions of Orthos with the world files it will be of great help with the digitizing. If not you can look at the world files to figure out the correct insertion point and scale for each Ortho.

Luck