Abstract: An interactive image data transmission system uses the expertise of an image end user distant from the image collection point. An image with a wide angle field of view is transmitted to the end user in lossy-compressed form. The image is displayed at the receiving end with errors introduced by the lossy compression. The end user can select and specify a narrowed field of view, and the image capturing parameters are modified as necessary under end user control to capture a desired image of the narrow view field. The transmitting station transmits a lossy compressed version of the narrow view image which is displayed for the user, and the user selects at least one window of definite interest within the image. Then, additional image data sufficient to provide a correct display within the window(s) of interest is transmitted to the receiving station and the display is updated within the window(s). The additional data may be difference data in a variable length diagonal code.