6-
The preparation of multi-image maps has proved to be a long and
arduous process particularly in color. Consequently an alternative
format was considered. The ERTS orbits are highly repeatable. NASA
can guarantee that the same scenes are repeated within a small tolerance
each time the spacecraft passes over an area. The nominal scenes have
been identified and coded alphanumerically for the entire world, and a
map series based upon the single image formats has been proposed.
The first image format map was prepared for the scene identified
as Upper Chesapeake Bay, which includes the cities of Washington, D.C.,
and Baltimore, Md. The map at scale 1:500,000 is printed in the color-
infrared rendition and carries a fitted UTM grid. Marginal data include
the scene indexed to the standard 1:250,000-scale line maps, a location
map at scale 1:2,000,000, and an explanation of the color printing code.
Comparable maps can be produced in about a month after receipt of coverage,
at a cost of less than $2000. They open the possibility of repetitive
mapping on a seasonal basis. Image-format maps are also being prepared
for all of the scenes i n the Florida State map and for other selected
areas throughout the country.
ERTS images have proved particularly valuable for mapping in
Antarctica, where the almost total lack of planimetric detail makes repro
duction at scales of 1:250,000, 1:500,000, and 1:1,000,000 appropriate (7).
The planimetric accuracy obtained from ERTS cartographic products
is summarized below (8).
Table 1.--Summary of ERTS MSS positional accuracy
Mode and form Error range (rms)
1 - 8 km
150 - 350 m
50 - 100 m
100 - 150 m
150 m
240 m
125 - 150 m
Referenced to lat/long indicators
Referenced to ground control
o Best fit to UTM projection
o UTM grid fitted to one single
band image
o UTM grid fitted to a single-band mosaic
of 2 to 4 images
o UTM grid fitted to multiband color
single image (lithographed)
o UTM grid fitted to multiband color
mosaic of 2 to 4 images (lithographed)
Precision processed to UTM projection
