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Alden P. Colvocoresses

Publications and source records attributed to Alden P. Colvocoresses.

26 records · Page 2Linked to original sources
USGS1978

Status of Space Oblique Mercator (SOM) projection (EC 64 Landsat)

The Space Oblique Mercator projection, a concept that was originated by Colvocoresses in 1974, has been mathematically implemented as the first map projection to provide continuous mapping of satellite imagery true to scale along the groundtrack, and within a few millionths of accurate conformal projection. Specifically designed for Landsat (formerly ERTS) imagery, it is also suitable for other satellites with broader scans. Formulas are given for both sphere and ellipsoid. A unique feature is the need for a curved groundtrack and skewed scan lines on the SOM projection, although they would be straight and parallel, respectively, on a normal oblique cylindrical projection.

Open-File Report↗
USGS1975

Information through color imagery

The color-sensing capability of the human eye is a powerful tool. In remote sensing we should use color to display data more meaningfully, not to re-create the scene. Color disappears with distance, and features change color with viewing angle. Color infrared film lets us apply color with additional meaning even though we introduce a false color response. Although the marginal gray scale on an ERTS (Earth Resources Technology Satellite) image may indicate balance between the green, red, and infrared bands, and although each band may be printed in a primary color, tests show that we are not fully applying the three primary colors. Therefore, contrast in the green band should be raised. For true three-color remote sensing of the Earth, we must find two generally meaningful signatures in the visible spectrum, or perhaps extend our spectral range. Before turning to costly digital processing we should explore analog processing. Most ERTS users deal with relative spectral radiance; the few concerned with absolute radiance could use the computer-compatible tapes or special annotations. NASA (National Aeronautics and Space Administration), which assigns the range and contrast to the ERTS image, controls processing and could adjust the density range for maximum contrast in any ERTS scene. NASA cannot alter processing for local changes in reflective characteristics of the Earth but could adjust for Sun elevation and optimize the contrast in a given band.

Journal of Research of the U.S. Geological Survey↗
USGS1974

Unique cartographic characteristics of ERTS

The ERTS television sensing system has unique cartographic advantages over aircraft and satellite film systems. These are longer life combined with greater coverage, transmission of data in near real time, orthogonality, excellent geometric precision for planimetric mapping, suitability for automation (because of the basically continuous image on a mathematically definable map projection), radiometric fidelity, and the extension of sensing capability to near-infrared wavelengths.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Autographic theme extraction

Remote-sensor images, including aerial and space photographs, are generally recorded on film, where the differences in density create the image of the scene. With panchromatic and multiband systems the density differences are recorded in shades of gray. On color or color infrared film, with the emulsion containing dyes sensitive to different wavelengths, a color image is created by a combination of color densities. The colors, however, can be separated by filtering or other techniques, and the color image reduced to monochromatic images in which each of the separated bands is recorded as a function of the gray scale.

General Interest Publication↗
USGS1972

Image resolutions for ERTS, SKYLAB and GEMINI/APOLLO

Early in 1972 the first Earth Resource Technology Satellite (ERTS-A) is scheduled for launch in near-polar orbit. It will carry three return-beam-vidicon (RBV) TB cameras and a multispectral scanner (MSS). In 1973 a post-Apollo manned space flight called SKYLAB will orbit the earth at an inclination of 50° to the Equator. In addition to other sensors it will carry a battery of six multispectral cameras identified as experiment S190. This paper compares the images expected from ERTS and SKYLAB with those already obtained from GEMINI/APOLLO, all in terms of the photographic criterion of resolution. Recently provided data have led to several changes in the resolution of ERTS-A forecast a year ago (Colvocoresses, 1970).

Photogrammetric Engineering↗
USGS1971

Mapping from space

Remote sensing of the earth promises to become an operational tool of the engineer and the scientist within the next few years. There are no real technical limits on the uses of data from space sensors. However, it is not practical to fly special missions, particularly in space, for each specific use. General-purpose, earth-sensing missions aimed at meeting a wide variety of requirements must be defined. Engineers must help define earth-sensing missions, based on the concepts of repetitive coverage, multispectral response, and spatial correlation.

Journal of the Surveying and Mapping Division↗
USGS1970

ERTS-A satellite imagery

The first satellite designed to survey the Earth's resources is scheduled to be launched in 1972. This satellite, known as ERTS-A, will telemeter frames of imagery each covering 100-nautical-mile squares of the Earth. Except for the internal anomalies in the sensor system, the imagery, after being properly scaled, rectified, and controlled, may be considered an orthographic view of the Earth and used as a planimetric photomap. The accuracy of this photomap will be limited, principally by the geometric fidelity of the sensor system rather than by external effects, such as relief displacement, which restrict the direct cartographic use of the conventional aerial photograph. ERST-A is not designed as a topographic mapping satellite but does have real potential' for thematic mapping particularly in areas now covered by topographic maps.

Photogrammetric Engineering↗