I know John Farley could tell you lots about the early Harrier moving map - a series of 35mm slides of 1/2 mill topo maps mounted on rollers and driven by rubber bands (literally). I cannot remember how the slides were mounted, but say 8 to a line, and when you 'went off the edge' of the end slide, a great whirring noise occurred and the whole assembly rotated to the next line at t'oher end. Being early INS it used to 'get lost' with montonous frequency and occasionally picked up its skirts and belted of hundreds of miles into East Germany at a great rate of knots.
I still have one of the later Harrier map displays, from aeromart anorakism days. I think the same model was also fitted to the Tornado. They were built by Ferranti as iirc, part of the FE540 ins system.
Internally, a pair of 35 mm film spools are mounted on a circular platform which is rotated by servo / gearhead assemblies, presumably from ins / compass heading data. Within the platform, the map is scrollable and there are effectively servoed x/y stages to index to the map point of interest. A map film is several tens of feet long and typically covers the whole of Northern Europe. It’s projected at selectable intensities by a halogen lamp in the rear of the case to a very directional fresnel lens on the front of the case. The front panel has various controls, including a zoom function.
Whatever the faults, these units are a work of art in mechanical engineering terms and a tribute to the ingenuity of their designers. Considering the technology of the time, the whole ins must have stretched the capabilities to the ragged edge. I had plans at one stage to get the unit running from standard gps nmea output, via a bit of microcontrollery, but too many other projects and lack of system info means that it’s still on the back burner.
Have all the AP reference numbers for the system, but though obsolete, it’s still 30 year rule, so no help from the usual sources. Any ideas ?…