actual distortion pattern is required for accurate mapping. Facili- 
ties for sensor calibration are not generally available, and there 
is no recognized responsibility for providing users with calibration 
data. Manufacturers could probably assume the responsibility to 
provide more calibration data, but user interest will be served 
better by an independent calibration. The facility may not have to 
do all the calibration work, but could rather serve to verify the 
calibration and distribute the information in a useful form. Until 
remote sensor equipment is reliably calibrated, both radiometrically 
and geometrically, it will be impossible to realize the potential of 
remote sensing and verify the scientific and legal status of the data. 
CARTOGRAPHY 
Almost all forms of remote sensor data require a cartographic 
format of some type,meaning a defined projection and coordinate system 
of acceptable accuracy. Sensor data often relate to a particular 
theme, such as water surface temperature, cloud cover, or vegetation 
classification, and thematic maps of the interpreted data are frequently 
prepared. Thematic maps are not new; geologic maps originally provided 
the impetus for better topographic base maps. However, recent advances 
in computer processing of images, multispectral color-additive viewers, 
and density slicing have resulted in an explosive increase in the num- 
ber of thematics. Many are made directly from films of the imagery or 
even from analog or digital tapes. It is probably a compliment to 
cartography that a cartographic format for data presentation is so 
often chosen. Unfortunately, however, the geometric quality of many 
thematics does not justify suffixing the term "map." Geometric dis- 
tortions exist within the imagery and can only be removed with adequate 
calibration data. The Return Beam Vidicon cameras on the ERTS satellite 
are an example of a frame-format sensor that required extensive cali- 
bration to permit removal of the various image distortions. A global 
set of ground control points are also required to reference the images 
to a cartographic projection and thereby satisfy the accuracy criteria 
of a map. The RADAM radar mapping project in Brazil is a similar 
situation, where considerable effort is directed toward maintaining a 
stable aircraft platform on a precise flight path. Additionally, the 
position of the aircraft and ground control are required for converting 
the radar mosaics into useful map products. 
With some sensors, such as infrared scanners, the geometry can 
be described theoretically, but practical applications of the theory 
are difficult. Many flights are at low altitude under turpulent 
conditions. The output data may have desirable interpretive or pic- 
torial qualities, but the map qualities of defined scale, conformality, 
and azimuth are missing. The register of other data with the first 
set is difficult, and quantitative measurements are unreliable. Con- 
siderable sophisticated processing can come to naught when data points 
cannot be registered to each other or referenced to the ground. 
Photogrammetrists and cartographers could help alleviate the 
problems by developing calibration techniques and map standards for