Slope display

[futrtrubl]

This is probably made moot by the planned configurable colours but I would like to use low/high rez slope display to follow the low/high rez altimeter way of using greyscale and colour. This would alleviate the issue of not being sure if an area has useful slope data and allows the use of a useful colour scale for the slope image since green currently covers the range from perfectly flat to guaranteed to tip over.

[DMagic1]

A more accurate slope indicator is something I want to add to the instruments window. It should be possible to get slope values for a very localized area, rather than the very broad values shown on the big map. It's something that could be combined with improvements to the big map/zoom map slope display.