-5-
Another black-and-white mosaic at scale 1:500,000 for the whole
State of Arizona was assembled on the Lambert conformal conic projection
with a fitted UTM grid. Versions were printed both without and with
the planimetric line detail from the standard map. One of the most
successful products combined the image base printed in sepia with the
planimetric detail in standard map colors. One feature that should be
noted is that the southeast illumination on ERTS pictures is opposite
to that normally employed for relief representation.
Making cartographic products from the color imagery made available
by ERTS-1 is considerably more difficult than from single-band black-
and-white imagery (5) . The first printed color ERTS map was of the
State of New Jersey, assembled from three consecutive scenes of a single
orbit.
The New Jersey mosaic was prepared by first enlarging the individual
black-and-white images from bands 4, 5, and 7 to nominal 1:500,000 scale
on continuous-tone stable-base film. The images from band 5 were then
mosaicked by contact printing to a new film through a set of exposure
windows to mask the frames and bleed together the adjoining images.
This eliminated the mosaic match line and the need to rephotograph a
paper mosaic with consequent loss of image quality. Mosaics of band
4 and band 7 were assembled similarly, using the band 5 mosaic as a
control base for positioning the images of the other bands. The three
separate bands were then screened for lithography, and the color image
appeared only at the final printing.
During this process no deformation was applied to the original ERTS
images. The resulting map is therefore on no recognized map projection.
In order to place the UTM grid on the map, a number of ground control
points were identified and their coordinates measured on the map. An
11-parameter projective transformation was then computed to obtain
a least-squares fit between the image and the UTM grid (6). The coordinates
of the grid intersections were computed, and the grid was ruled. Although
the grid lines are straight, they are slightly nonparallel and of slightly
different spacing, but the differences cannot be visually detected. Any
UTM coordinates measured from the nearest grid intersection will be quite
accurate. However, the overall accuracy of the map did not quite meet
NMAS for 1:500,000 scale.
A second color-image base map has been compiled for the whole State
of Florida. This State extends across 7 ERTS orbits and lies in two UTM
zones so that 18 ERTS scenes are required for complete coverage. A plani
metric block adjustment of the images was computed to determine the conformal
enlargement of each image constrained to fit the adjacent images as well
as the control. The results were surprisingly good with an rms of 105 m.
The estimated accuracy of well-defined points referenced to the fitted UTM
grid on the final map is 150 m, which meets NMAS for scale 1:500,000.