John Grebenkemper looks
at
The 1842
Island Lake Views of Charles Preuss
  As
above, and on other pages on this website I have presented
images rendered from U.S.G.S.
DEM files--Digital Elevation Model. The DEMs were merged
with a shareware application called MacDEM,
and the 3D rendering was done with POV_Ray--a
freeware raytracing application. The view angles and
elevation can be set with Cartesian coordinates (z,y,z):
positive y is up, positive x is east, positive z is north.
The POV rendering at the top of this page makes a convincing
identification of Frémont's expedition cartographer
Charles Preuss's general vantage for the drawing at right,
but cannot look precisely from the terrestrial coordinates
from which original view might have been made. Notice that
in my low angle view, the lake is nearly hidden behind
higher foreground features.
But now, a step beyond POV!
 I
have had (summer 2003) some email correspondence with
John Grebenkemper of Saratoga, CA. John is an
accomplished climber, and is very familiar with the Wind
River chain, but before making another planned trip to the
area, he wondered just where Charles Preuss might have stood
when he made his drawing of Island Lake.
So John wrote his own computer program to render the DEMs
using Mathematica.
With the program that John created, he can look at a scene
from any map coordinate and determine just what can be seen,
and what cannot. Elevation and azimuth scales are part of
each of these renderings which he has sent--much reduced in
size here.
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 Bob;
I've finally got my program fully
debugged and it can produce images from
the DEM data. I'm sending 4 jpegs of
various locations that Preuss could have
drawn Island Lake from. The lowest
(A) is
likely very near the actual drawing
location of the left half of the picture.
It is clearly drawn from a location that
is not much above Island Lake. The second
one
(B) is
close by to the first, but at a higher
elevation. The perspective is clearly
getting to be wrong.
The third one
(C) is
too high, but gives a better view of the
right half of the picture. Elephant Head
is in the foreground and blocks the higher
elevations behind it. The highest
(D)
shows a better view of the peaks on the
right half, but is clearly wrong for
Island Lake which is on the left edge of
this view.
You may use these images on your web
site if you wish to illustrate the
problems in locating the Preuss drawing
location of Island Lake.
-John Grebenkemper
Note: John
Grebenkemper was elected to the American
Alpine Society more than 20 years ago and
has climbed in the US and South America.
He holds a Ph.D. from Stanford University
in the field of Radio Astronomy and
currently works on designing commercial
fault tolerant computer systems. An
amateur historian, his interests are
primarily focused on the Oregon-California
emigrant trails in the period of the
1840's.
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 A
N43 05 02 W109 38 20
|
 B
N43 05 02 W109 38 30
|
 C
N43 04 30 W109 37 56
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 D
N43 04 30 W109 37 56
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The two views below are taken from
Which
Mountain Did Frémont
Climb?
John Grebenkemper
November 23, 2004.
The Drawing by Charles Preuss is from the 1843
government printing of the report of the 1842
expedition.
Frémont, August 13, 1842: " This road
continued for about three miles, when we suddenly
reached its termination in one of the grand views
which, at every turn, meet the traveler in this
magnificent region. Here the defile up which we had
traveled opened out into a small lawn, where, in a
little lake, the stream had its source.
Image Generated From USGS DEM Files South Of
Lost Lake At N43° 04' 04" W109° 40'
05"
This paper also contains thoroughly rigorous
scientific examination of the Frémont
barometric observations in the Wind River
Range
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Part of the difficulty of exact duplication of the 1842
drawing is that the plates that accompany the Frémont
Reports are lithographs made from the original sketches and
drawings by expedition cartographer Preuss. One particular
vantage may not have provided Preuss the complete view that
he wanted, but John's DEM renderings show what Charles
Preuss could have seen from various positions.
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