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when the images are printed by the EBR, Colvocoresses has suggested that they can be produced 
on a Space Oblique Mercator projection [1 0] . This is a continuous, cylindrical, conformal, pro- 
jection with a scale distortion of less than 1 part in 10 000. 
All cartographic problems of using ERTS data have certainly not been solved. Maintenance 
of resolution through the many photographic steps is a major problem. However, it has been de- 
monstrated that 1:500 000 is about the optimum scale, for presentation as opposed to the 1:1 000 000 
scale predicted before launch. Obtaining proper color balance is another problem ; the same scene 
processed by different laboratories may look totally different. It has been found that good color 
quality for mapping can be obtained using only bands 5 and 7. This does not imply that there is not 
additional information for multispectral analysis in bands 4 and 6, but simply that for pictorial pur- 
poses bands 5 and 7 are sufficient. Some map users object to the overall red impression obtained 
from the conventional presentation of the color infrared response. Attempts have been made to 
assign other colors to obtain a more natural appearance. Attempts have been made to use the mul- 
tispectral characteristics to produce color separations for water and infrared reflective vegetation, 
but these have not yet been carried to printing of maps. Considerable more work is required to 
make maximum use of the parameter of color available from the ERTS records. 
Cartographic Results from Skylab 
  
Skylab was launched by NASA primarily to determine the ability of men to operate for 
extended periods in space. A second objective was a series of astronomical and solar physics 
experiments. The third priority was a set of Earth observation experiments, two of which invol- 
ved photographs [11] : 
The first system was an array of six nearly identical cameras identified as S-190A. These 
cameras had a focal length of 150 mm, a format of 57 x 57 mm on 70 mm film, covered a ground 
area of 165 x 165 km at an image scale of 1:2 900 000. The film and filters were selected to give 
four black-and-white spectral bands approximately equivalent to those provided by the MSS on 
ERTS-1. Full color and color infrared films were carried in the remaining two cameras. Flight 
patterns were designed to provide repeated coverage over a number of test areas in the United 
States. Because of the requirement to schedule photographic passes a day in advance, much of the 
photography is obscured by partial or total clouds. À small amount of coverage was also obtained 
over other parts of the globe. 
Pre-mission estimates of ground resolution were about 40 m for the color and high reso- 
lution black-and-white films, and about 60 m for the color infrared and black-and-white infrared 
films. These values were obtained on the original film, but second generation positives from the 
color films were degraded to nearly 80 m [12 . The high resolution black-and-white film easily 
withstands enlargement of more than 10X to scale 1:250 000. 
Most of the experiments conducted with the S-190A photography have been designed to 
investigate multispectral signatures at higher resolution than provided by ERTS-1. 
A few cartographic experiments have been undertaken but have not yet reached the stage 
of final production. A black-and-white mosaic of 4 frames from band 5 (0. 6 to 0. 7 nm) is being as- 
sembled at scale 1:250 000 as an image base for a standard map sheet in the Hartford, Connecticut, 
area. The amount of cartographic assist for this photomap has not yet been decided. An attempt 
has also been made to do map revision at scales 1:1 000 000 and 1:250 000 using enlargements from 
S-190A photographs. Existing maps at these scales have been assembled from larger scale maps 
with consequent dislocation of features and generalization of shapes. The S-190A photography shows 
most of the map worthy features. But in general the resolution is inadequate to permit classifica- 
tion, and compilers are frustrated in deciding what they are looking at and whether it is worthy of 
change. No geometric accuracy tests have yet been made on these experiments. 
The second photographic experiment on Skylab was a single long focal length camera known 
as S-190B. It had a focal length of 460 mm, a format of 115 x 115 mm, covered a ground area of 
109 x 109 km at an image scale of 1:945 000. Several different films were used at different times, 
but most of the pictures were taken with color (S0-242) or color infrared (3443) film. On Skylab 4 
a new color infrared film(S0-131) having a resolution comparable to the best cotor film was carried. 
The first pictures look excellent but have not yet been evaluated. 
The coverage pattern for S-190B is similar to that for S-190A except that the ground track 
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