Re: [photo-3d] Re: Hyperstereo artists?, aerial topography

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

Actually, I was going to say "the entire world", but I wasn't absolutely
sure of that, whereas I was of the United States.  Certainly most of the
world.   I was being conservative to be on the safe side.

Regarding aerial coverage, areas of strategic or economic interest get more
coverage, as you indicated, with more frequent reshoots.

Regarding satellite imagery, the resolution, while astounding, still cannot
match that of aircraft flying at 1,000 to 2,000 feet altitude (625 to
1250km).

Also, the other problem with satellite photography is that some part of the
world is always covered with cloud cover, so it is not possible to cover all
areas in the same pass.  Rather, mosaics are gradually built up from
"sections" as they are revealed.

This is why I question whether the entire world has been covered at this
time.  With today's technology it might be easier to get full coverage of
the moon or Mars than the earth.

Otherwise, your descriptions are quite accurate and well stated.

Also, I feel that it is quite likely that most if not all of us live in
areas that have been covered and are available, since high security areas
are usually restricted as to public access, let alone residency.

JR

----- Original Message -----
From: "Abram Klooswyk" <abram.klooswyk@xxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Sunday, October 22, 2000 8:03 AM
Subject: [photo-3d] Re: Hyperstereo artists?, aerial topography


> John A. Rupkalvis 21 Oct 2000:
> >These (which very possibly could be the largest single use of
> >stereo photography of all) are the twin pass aerial images
> >made for aerial mapping. They have to be in stereo for
> >drawing isolines on topographic maps, delineating height
> >boundaries.  I understand that the entire United States has
> >been mapped this way.
>
> The entire United States? The entire world you probably mean.
> And apart from airplanes, some satellites are making stereo
> images all day, also this very moment, the circumpolar tracks
> form stereopairs 90 minutes apart for example. Some of the most
> detailed images are held secret, having military significance,
> but some are publicly available.
>
> The topographical institutes of many (at least the western)
> countries have files of mostly 60% overlapping air photographs
> which often go back to the 1920-30s, and are often repeated
> every 5 or 10 years, depending on population density and wars.
>
> Already since many years I have some of these vertical aerial
> stereopictures of my house with surroundings. I just had to
> give the topographical coordinates to our national topographic
> institute and could _borrow_ the picture set for free to copy
> them (this is no longer possible now in this country, you have
> to buy prints :-().
>
> Depending on security restrictions, I guess that you can order
> similar aerial stereo pairs from your living area.
>
> Abram Klooswyk
>
>
>
>
>