Is there spatial reference with your images? You mention lat/lon values but jpeg itself does not support map information except in an external world file. In this case, ENVI will not be aware of any georeferencing so placement in the display may not be correct. If there is also an ENVI header file with some map information or geographic corners, then ENVI will be able to provide some georeferencing or a pseudo projection. Georeferencing of at least one file is required in the Image to Image registration when automatically generating tie points. The help states that you will need at least 3 or more tie points in order for ENVI to generate additional tie points. If you provide 3-5 tie points, you should be able to use the Auto Tie point generation in the Image to Image registration workflow. The parameters for automatic tie point generation are in the 'Main' tab and after you have selected seed points, you should be able to select 'Next' in order for ENVI to automataically generate tie points.

MariM, Thanks for replying - I was probably over generalizing my description (my apologies). To answer your question, the .JPEG has no .JPW file (as the images are not georeferenced). Each JPEG image was converted from a raw .DNG file with an associated .NFO file (info). The .NFO file contains flight information from the sensor at the time that each image was captured. The .NFO File includes such information as the date, time, camera info (sensor type, focal length, instantaneous filed of view etc.), image width/height, GPS Lat/Long in Radian and in Degrees, GPS Altitude, and Vehicle information such as Pitch, Yaw, and Roll. As part of another process (and because ENVI doesn't read .DNG files) A converter was used to go from .DNG > .JPG. During the conversion process, an EXIF (Exchange Image File Format) format converts the information in the .NFO file and stores it in the .JPG file metadata with the appropriate Metadata tags. We have been using a 3rd party software called Pix4D that has the ability to read the metadata from the .JPEG, and georeference and mosaic a large number (thousands) of images all at once. I am trying to determine if it is possible to do something similar at a smaller scale (only a few images) in ENVI, with the same data. So my first task was to find a way to georeference the images. This is what I described in the original message, and I did this by manipulating a .pro file that I received to extract information from the original .NFO file. The information that I extracted included the GPS Latitude (in degrees), GPS Longitude (in degrees), and the Yaw - rotation (in degrees). It is my believe that the Lat/Long Coordinates are for the Lower Left corner of the image. After running the script, the images have all been placed in the approximately correct geographic space but they do not overlap well enough to run a mosaic. This is where I started to explore the capabilities of ENVI to generate tie points automatically. If I only had to do the process a few times, I don't think that it would be an issue to generate tie points manually, but if I have multiple images - the process becomes more time consuming and a less viable option. Thanks for your time, and sorry for the wall of text. Chris

That sounds like a pretty good process. If you want to try and automatically generate tie points, I would suggest you have at least one georeferenced image of known accuracy to which you can georeference all other images. If one image is georeferenced, you should be able to generate tie points automatically. But the accuracy of the tie points will very much depend on the accuracy of the georeferenced image and the quality of the other images because the algorithm has to find areas of similarity.

Well, thanks for the input - the tips are much appreciated. I'll continue to work on this, and if I get a desirable product, I'll let you know what methods I used. Chris