I have various gigapans of rock outcrops which I would like to export and annotate in a program like Illustrator or Canvas. I want to be able to overlay parts of the image with shapes and lines. Does anyone know how I can accomplish this? I exported a gigapan as a .tif and .raw and neither will open with illustrator or canvas or powerpoint. Thank you!

I would recommend annotating the GigaPans in Photoshop rather than Illustrator or Canvas, presuming you want to retain the gigapixel resolution. Otherwise just downsize and convert it into a jpeg and then open it in Illustrator or Canvas.

The first question I would ask is what will be the final size and use of the annotated piece? I would reduce the Gigapan to the desired size (say, 8 1/2 × 11) and keep the resolution at about 300ppi (not to be confused with dpi which is output resolution). This way your image is still sharp, but not unnecessarily large.

Then I would import it into Illustrator and apply the typography and other annotating graphics there. By doing the latter in Illustrator, you will assure the type looks sharp and not bit-mapped if you are dealing with either small type or fine serifs.