We investigate two interactive techniques for registering an image to 3D digital terrain and building models. Registering an image enables a variety of applications, including slideshows with context, automatic annotation, and photo enhancement. To perform the registration, we investigate two modes of interaction. In the overlay interface, an image is displayed over a 3D view and a usermanually aligns 3D points to points in the image. In the split interface, the image and the 3D view are displayed side-by-side and the user indicates matching points across the two views. Our user study suggests that the overlay interface is more engaging than split, but is less accurate in registration. We then show several applications that make use of the registration data.