The preparation of multi-image maps has proved to be a long and arduous process - parti- 
cularly in color. Consequently an alternative format was developed. The ERTS orbits are highly 
repeatable. NASA can guarantee that the same scenes will be repeated within a small tolerance each 
time the spacecraft passes over an area. These nominal scenes have been identified and coded alpha- 
numerically for the entire world, and a map series based upon these 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, Maryland. The map at scale 
1:500 000 is printed in the color-infrared rendition and carries a fitted UTM grid. Marginal data 
includes 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. These maps can be produced in about 
one 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 in 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 reproduction at scales of 1:250 000, 1:500 000, and 
1:1 000 000 appropriate [7]. 
E 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) 
Referenced to lat/long indicators 1 -8km 
Referenced to ground control 
Best fit to UTM projection 150 - 350 m 
UTM grid fitted to single-band mosaic of 
2 to 4 images 100 - 150m 
UTM grid fitted to multiband (colored) 
single image (lithographed) 150m 
UTM grid fitted to multiband (colored) 
mosaic of 2 to 4 images (lithographed) 240 m 
Precision processed to UTM projection 125 - 150m 
Some experiments have been performed to determine the utility of ERTS imagery for im- 
proving the rendition of terrain features on aeronautical charts, and for refining coastal and shallow 
water depiction on nautical charts, but these have not yet been carried to the stage of complete 
products. 
In all of the products described above, the imagery has been used without any change in 
geometry other than simple enlargement. The map reference system defined by the UTM grid has 
been warped to fit the imagery. A more cartographically appealing approach would be to warp the 
imagery to fit the map projection and reference grid. This has been accomplished in a completely 
digital system developed by IBM [9] . Other investigators are also pursuing completely digital 
approaches to interpretation as well as geometric correction. 
The ERTS image data can be supplied by NASA as Computer Compatible Tapes (CCT) con- 
taining the intensity level in an xy array of picture elements (pixels). Both the radiometric intensity 
and the position of the pixels can be manipulated in the computer. By comparison of input image 
coordinates to ground control point UTM coordinates, the geometric correction parameters may be 
computed. The output image is then mapped to the input image and the intensity of the nearest neigh- 
bouring pixel is assigned.The corrected images are then printed on a drum recorder. Excellent 
image quality has been obtained, the output grid is on a true UTM projection, and the accuracy is 
compatible with NMAS for scale 1:250 000. 
The observed high geometric integrity of the MSS images has prompted an investigation 
into the actual geometry of the records. By making changes in the geometrical corrections applied 
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