High!

Everybody is talking about GoogleEarth... even in less high 
tech-enthusiastic countries like Germany, the issue made it into prime 
magazine stories. But as GoogleEarth aims to be a real-time navigable 
representation of our planet, its level of detail is limited and far 
from photorealistic. As a commercial, proprietary project, the satellite 
and aerial imagery also is tagged over and over with those annoying "(C) 
2005 Google" watermarks. Then, for vast parts of Earth's land mass, 
GoogleEarth's satellite maps are of lower resolutions as publicly 
available nowadays (for example the Landsat series).

So what about starting a PoVEarth project? There are terabytes of public 
domain NASA/JPL image mosaics available, down the line at 0.5 arcseconds 
/pixel, which equals about 15 m/pixel on the equator. And not only image 
mosaics, but also altimetry data at a horizontal and vertical resolution 
high enough to do it without vertical exaggeration (3 arcseconds per 
sample, 1 metre vertical accuracy)! In my last rendering of Afghanistan, 
I used one of these 1 by 1 degree tiles...

We could start with an overview representation of the Earth made of,
let's say, 5 by 5 degree image mosaic tiles and the less accurate 
GTOPO30 altimetry data (15 arcseconds per sample, yet still 1 metre 
vertical accuracy) and then gradually filling in with the more precise 
datasets.

Quite a challenge would be the color adjustment of the tiles, as they 
were photographed during several Space Shuttle Radar Topography Missions 
(SRTMs) in 2000 and 2001, so frequently adjacent portions of the tiles 
were shot at different daytimes and seasons, consequently showing 
different lighting angles, vegetation status and snow cover (an example: 
Tierra del Fuego on http://makeashorterlink.com/?H130237CB - note the 
sharp boundary between mountains deep in snow and almost snow-free or 
between dry reddish and lush green pampa!

At a later stage of development, we could again start filling in even 
larger-scaled altimetry data derived from printed maps (for example 1 : 
25.000 topographic maps) and converted from geodesic to simple 
cylindrical projection, same with aerial photographs replacing satellite 
images... this also would be the time to start populating the landscape 
with actual single rocks, trees and buildings.

After the first "overview" modeling, each participant of the project 
might start modeling one certain place, region or country more 
thoroughly - whether this might be his or her home town or some other 
area of personal interest. With me, this would include the Cologne area, 
of course Afghanistan and some subantarctic islands...

We PoV people don't have billions of dollars behind us. But we have 
thousands of gifted and enthusiastic programmers and multimedia geeks, 
and, most important, no deadline! No banks and shareholders would 
prevent us from embarking upon a decades- or even centuries-long 
raytracing adventure which only the grandchildren of our grandchildren 
live to complete. This soon could develope into one of the largest and 
longest-lasting non-profit computing enterprises ever undertaken...

So, now what about PoVEarth?

See you in Khyberspace - and not only there!

Yadgar

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