Originally posted by alphaMegas
reply to post by Illustronic
am not finished yet.
now try looking at it again matey.
OK, let me walk you through the kind of process you are viewing on Google Mars, or any space based simulated terrain model. What you have is an
elevation map generated from the resolution of the actual data, that being a digital image (though derived from special laser equipment using
reflected impulse distance measurements) but it is ultimately held hostage to the number of pixels in the raw data, 'the resolution' of the
So here I took a NASA satellite image of the Iraq Gulf region, it is quite large at 60 MB, (I tried to scale it down for easy viewing here).
I wanted a quick and easy way to make a landscape and 'fake' an actual DEM elevation
to terrain model, it was good enough but not real. An actual elevation terrain DEM model would have the white as the highest elevations and
the darks as recessions, turned to grayscale it looked OK for doing little work.
So below is a dramatically lit fake landscape a UAV Hunter is flying an autonomous mission over, done solely for dramatic effect (and quick and dirty
mind you) but will illustrate an education for you.
So, looks OK like a real landscape complete with a real shoreline, sort of. Now we take that really high resolution satellite image and zoom on down
to see the surface look what happens.
The 3D software program is so sensitive that it starts to image the individual pixels as elevation changes, and of course that would be geometric,
like squares because that area you see a detail of is ten thousands of the area of the whole image, thus individual pixels are imaged.
Here's what takes place in faking a real DEM map.
There is a pixel count in the data, this data is loaded into a real elevation 3D terrain model, as you see the contrast was equalized a bit because
the modulation changes in loaded data has less color breaks than real laser elevation DEM data does, so you can't see the individual pixels in the
loaded data, until you realize you just loaded 1,000 km and you are looking at an image that is just a couple km, and the software picks up individual
pixels changes as geometric elevation changes, thus geometric shadows thus NOT REAL!.
Now after all of that they take whatever color image they took of that same area, (me starting with a colorized NASA satellite image I knew the color
would match the fake elevation map I made), so they 'skin' that terrain model with the color from a color digital image (like Google Earth does)
also held hostage to the resolution that may or NOT match up with the terrain model.
I admit I didn't present a true color image of the map I made but with the terrain you should get the message, you are not looking at a photograph of
the Mars terrain, you are looking at a terrain map with a resolution limit.