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Geology topics

Sherman S.C. Wu

Publications and source records attributed to Sherman S.C. Wu.

6 recordsLinked to original sources
USGS2012

Photogrammetric portrayal of Mars topography

Special photogrammetric techniques have been developed to portray Mars topography, using Mariner and Viking imaging and nonimaging topographic information and earth-based radar data. Topography is represented by the compilation of maps at three scales: global, intermediate, and very large scale. The global map is a synthesis of topographic information obtained from Mariner 9 and earth-based radar, compiled at a scale of 1:25,000,000 with a contour interval of 1 km; it gives a broad quantitative view of the planet. At intermediate scales, Viking Orbiter photographs of various resolutions are used to compile detailed contour maps of a broad spectrum of prominent geologic features; a contour interval as small as 20 m has been obtained from very high resolution orbital photography. Imagery from the Viking lander facsimile cameras permits construction of detailed, very large scale (1:10) topographic maps of the terrain surrounding the two landers; these maps have a contour interval of 1 cm. This paper presents several new detailed topographic maps of Mars.

Journal of Geophysical Research Solid Earth↗
USGS1973

Remote sensing and photogrammetric studies: Appendix to Part C: effect of photogrammetric reading error on slope-frequency distributions

Lunar slope-frequency distributions obtained by photogrammetric techniques are compared with results from the bistatic-radar investigations of the Apollo 14, 15, and 16 missions (refs. 33-16, 33-17, and 33-32) and of Explorer 35 (ref. 33-27). Algebraic standard deviations of slope-frequency distributions from photogrammetric data are equivalent to rms slopes of slope-frequency distributions from bistatic-radar data. Photogrammetrically derived algebraic standard deviations of the distributions are often larger than those obtained by the radar (ref. 33-25) when photogrammetric results at 25-, 200-, and 500-m slope lengths are compared with rms slope estimates from Apollo S-band (13-cm wavelength), Apollo VHF (1.16-m wavelength), and Explorer 35 (2.2-m wavelength) radar.

Book chapter↗
USGS1973

Remote sensing and photogrammetric studies: Part D: repeatability of elevation measurements--Apollo photography

Stereoscopic photographs of the Moon taken by the metric and panoramic cameras on board the service module of Apollo spacecraft provide a source for quantitative data on lunar topography. The accuracy of the topographic data depends, in part, on the repeatability of elevation measurements. The repeatability depends on contrast in the stereoscopic image and is affected by many factors, such as photographic quality, the photogrammetric instrument used, and illumination conditions. For the Moon, illumination conditions are important so that repeatability of elevation measurements may be statistically related to Sun elevation angles, local slopes, and albedos of surfaces. We have examined the effect of Sun elevation angle on repeatability, using Apollo 15 photographs (Wu, unpublished data), and extended the results to slope-related effects.

Book chapter↗
USGS1972

Orbital-science investigation: Part C: photogrammetry of Apollo 15 photography

Mapping of large areas of the Moon by photogrammetric methods was not seriously considered until the Apollo 15 mission. In this mission, a mapping camera system and a 61-cm optical-bar high-resolution panoramic camera, as well as a laser altimeter, were used. The mapping camera system comprises a 7.6-cm metric terrain camera and a 7.6-cm stellar camera mounted in a fixed angular relationship (an angle of 96° between the two camera axes). The metric camera has a glass focal-plane plate with reseau grids. The ground-resolution capability from an altitude of 110 km is approximately 20 m. Because of the auxiliary stellar camera and the laser altimeter, the resulting metric photography can be used not only for medium- and small-scale cartographic or topographic maps, but it also can provide a basis for establishing a lunar geodetic network. The optical-bar panoramic camera has a 135- to 180-line resolution, which is approximately 1 to 2 m of ground resolution from an altitude of 110 km. Very large scale specialized topographic maps for supporting geologic studies of lunar-surface features can be produced from the stereoscopic coverage provided by this camera.

Book chapter↗
USGS1972

Photogrammetry and altimetry: Part C: frequency distributions of lunar slopes

The metric and panoramic cameras aboard the Apollo 16 spacecraft provided photographs on which photogrammetric techniques may be used to obtain precise measurements of horizontal distances and elevations. These measurements of horizontal distances and elevations. These measurements may in turn be used to obtain slope-frequency distributions of lunar surfaces at various slope lengths and for various types of terrain and geologic map units (ref. 30-4). Bistatic radar and photoclinometric methods have also been used to obtain slope-frequency distributions of lunar surfaces. The problem arises as to how well these varied methods correlate with one another (ref. 30-5).

Book chapter↗