I did that too, for about five years in the 70s. It was a totally analog technology at the time, working with film emulsions and optical/mechanical devices. Its all done with computers nowadays. Look in Space>I would like to check this out>Tell me about it (2014-09-16)for details on this 3d plotting equipment.

GIS is graphics software for mapping spatial data stored in tabular databases, although it can also interface with digital imagery. GIS is a lot like CAD, except its for maps, not engineering drawings.

Image processing works with raster data, digital images, like the output of satellite sensors or digital cameras.

Image processing is about processing image data and enhancing it so it makes more sense to the human eye and brain. It acquires and displays new ground data. GIS is about displaying tabular data in cartographic form. It depicts already-known known information, data gathered by other means (like photography, image processing and remote sensing).