Engineering topics

Bridges, P. M.

Publications and source records attributed to Bridges, P. M..

4 records

NASA NTRS1985

Mars Planimetric Mapping

The 1:5,000,000 scale shaded relief maps of Mars originally compiled from Mariner 9 pictures are being upgraded by adding details visible on Viking Orbiter images. This work is done by modifying the original airbrush drawings; no attempt is made to reposition features according to the latest control nets. Thirteen of these maps have been published to date, two are in compilation, and two are in press. A hard cover atlas containing reduced scale versions of all Mars cartographic products will be published upon completion of the revisions of the 1:5,000,000 scale maps, the 1:2,000,000 scale photomosaics, and Mars color albedo mapping tasks. This atlas will supersede the existing Atlas of Mars prepared by Batson and others.

Batson, R. M.↗

NASA NTRS1985

Voyager Cartography

The Jovian and Saturnian satellites are being mapped at several scales from Voyager 1 and 2 data. The maps include specially formatted color mosaics, controlled photomosaics, and airbrush maps. More than 500 Voyager images of the Jovian and Saturnian satellites were radiometrically processed in preparation for cartographic processing. Of these images, 235 were geometrically transformed to map projections for base mosaic compilations. Special techniques for producing hybrid photomosaic/airbrush maps of Callisto are under investigation. The techniques involve making controlled computer mosaics of all available images with highest resolution images superimposed on lowest resolution images. The mosaics are then improved by airbrushing: seams and artifacts are removed, and image details enhanced that had been lost by saturation in some images. A controlled mosaic of the northern hemisphere of Rhea is complete, as is all processing for a similar mosaic of the equatorial region. Current plans and status of the various series are shown in a table.

Batson, R. M.↗

NASA NTRS1976

Applied photo interpretation for airbrush cartography

New techniques of cartographic portrayal have been developed for the compilation of maps of lunar and planetary surfaces. Conventional photo interpretation methods utilizing size, shape, shadow, tone, pattern, and texture are applied to computer processed satellite television images. The variety of the image data allows the illustrator to interpret image details by inter-comparison and intra-comparison of photographs. Comparative judgements are affected by illumination, resolution, variations in surface coloration, and transmission or processing artifacts. The validity of the interpretation process is tested by making a representational drawing by an airbrush portrayal technique. Production controls insure the consistency of a map series. Photo interpretive cartographic portrayal skills are used to prepare two kinds of map series and are adaptable to map products of different kinds and purposes.

Inge, J. L.↗

NASA NTRS1976

Applied photo interpretation for airbrush cartography

Lunar and planetary exploration has required the development of new techniques of cartographic portrayal. Conventional photo-interpretive methods employing size, shape, shadow, tone, pattern, and texture are applied to computer-processed satellite television images. Comparative judgements are affected by illumination, resolution, variations in surface coloration, and transmission or processing artifacts. The portrayal of tonal densities in a relief illustration is performed using a unique airbrush technique derived from hill-shading of contour maps. The control of tone and line quality is essential because the mid-gray to dark tone densities must be finalized prior to the addition of highlights to the drawing. This is done with an electric eraser until the drawing is completed. The drawing density is controlled with a reflectance-reading densitometer to meet certain density guidelines. The versatility of planetary photo-interpretive methods for airbrushed map portrayals is demonstrated by the application of these techniques to the synthesis of nonrelief data.

Inge, J. L.↗