ARBITRARY PHOTOCOORDINATE PASS POINTS

Pass points used to orient stereomodels in map compilation are usually selected as discrete objects or points on the ground that appear in each image. The Geological Survey is testing the feasibility of using arbitrary photocoordinate positions as pass points rather than discrete points marked on the photographs. The most recent test has used the TA3/P1 stereocomparator, but the procedure is designed for use with three analytical stereoplotters now on order.

For testing the procedure, pass points on 50 unmarked photographs were measured in four strips. Previous data using marked points were available for comparison. The triangulation results of the two methods were not significantly different, indicating that the elimination of the point-marking phase prior to point measurement is a main advantage of the procedure.

MAPPING FROM HIGH-RESOLUTION HIGH-ALTITUDE PANCHROMATIC PHOTOGRAPHS

The relative imagery characteristics of Kodak 2402 and high-resolution SO-022 panchromatic films, exposed in a standard mapping camera at high altitudes, have been investigated. Results indicate that the resolution on Kodak SO-022 film was only slightly higher than on 2402 film using photographs taken at 40,000 feet above mean terrain with a 6-inch focal-length camera.

The anticipated image motion at a 40,000-foot altitude with an airspeed of 400 knots is 7 feet ground scale during an exposure of 0.01 second. No appreciable difference in resolution could be observed between a target oriented along the flight line and one oriented across the flight line. This would indicate that for high-altitude photographs image motion is not a predominate factor in resolution problems.

Both geometric accuracy and the ability to photoidentify and to plot required map detail fell slightly short of meeting map accuracy standards. Enough promise does exist, however, to continue the search for a highresolution film-camera combination that will satisfy mapping requirements using high-altitude photographs.

FORMATION OF DIGITAL FILES DIRECTLY FROM STEREOMODELS

Techniques were developed for collecting digital data during stereocompilation using an analog stereoplotter equipped with digital data collection hardware and file

building strategy for Digital Line Graph-2 (DLG-2) data files. The DLG-2 files consist of line map information edited to add attribute codes and to remove visible errors and inconsistencies. The procedure is divided into data collection, data processing, and interactive editing. The project has shown that stereomodel digitization and the subsequent editing of these data are within the state-of-the-art and appear to be feasible in areas of low relief, such as the plains area of the Midwest. As a result of this work, flexible procedures for digitizing and editing stereomodel data have been adopted, and these procedures are being tested.

PLANIMETRIC COMPILATION FROM ORTHOPHOTOGRAPHS

The Survey has developed and put into operation an economical method for using orthophotographs in the topographic mapping process. For each new mapping project at 1:24,000 or 1:25,000 scale, two levels of photography are exposed, high altitude for producing an orthophotograph base and low altitude for compiling contours. Aerotriangulation with the high-altitude photographs requires much less horizontal ground control than is needed for lower altitude photographs. Using photogrammetric instruments, high-altitude photographs are transformed into orthophotographs, each covering a 7.5-minute quadrangle area. The orthophotoimage is registered to a base sheet and is then printed on material allowing for direct scribing of features.

By reference to field-annotated photographs, all planimetric features that can be seen clearly on the image base are scribed in final form directly on the image. Several image bases are used so that the features can be color separated for printing. Each color separation is overprinted on the other bases in a prescribed sequence so that precise register of the separations is maintained throughout the process.

The stereomodels formed from the lower altitude photographs are scaled to discrete image points on the orthophotobase. Contours and other map features not clearly visible on the image base are compiled from the stereomodels. The contours are scribed in final form on a separate base, and the other stereocompiled features are transferred and scribed on the appropriate base. The completed scribed drawings are used to prepare color composites for the editing and subsequent final copy for preparation of pressplates.

The photobase mapping process reduces the cost and time to produce a standard topographic map by eliminating aerotriangulation of the many low-altitude photographs and by avoiding the preparation of manuscript copy prior to color-separation scribing. A companion orthophotoquad may be prepared as a byproduct of the process.

MAPSAT-AN AUTOMATED MAPPING SATELLITE

The Geological Survey has been investigating the concept for a satellite that, by continuous imaging with very high geometric fidelity in epipolar planes, will permit three-dimensional automated mapping of the Earth from space. Such a satellite, Mapsat, would use linear arrays of detectors to view a ground swath across the ground track of the satellite. Multiple arrays would provide both stereoscopic and multispectral imaging.

LANDSAT 3 RETURN BEAM VIDICON IMAGES

Landsat 3, launched on March 5, 1978, carries longer focal length return beam vidicon (RBV) cameras that provide substantially improved resolution and geometric fidelity as compared with the RBV's of earlier Landsats. Preliminary evaluation of the RBV images found that, while the normally produced images were lacking in image quality, specially processed images were excellent. When the new National Aeronautics and Space Administration (NASA) digital Image Processing Facility and the Earth Resource Observation Satellite Digital Image Processing System become fully operational, normal image quality is expected to be much better.

In an investigation on Landsat 3 RBV images, four RBV scenes of the Upper Chesapeake Bay were analyzed for geometric quality. (The RBV images are central perspective images with a narrow field of view.) Control points were identified on 1:24,000-scale topographic maps, and the RBV images of these points were measured on a comparator. A direct similarity transformation from image coordinates to Universal Transverse Mercator ground coordinates yielded a root-mean-square error of approximately 300 feet.

SATELLITE IMAGE MAPS

Lunar and planetary mapping

A project is underway to produce 1:250,000-scale lunar orthophotographs from high-oblique Apollo mapping camera photographs. The NASA Lunar and Planetary Photography and Cartography Committee has requested Survey support in extending orthophotocoverage into additional lunar areas covered by oblique photographs to complement the maps produced by DMA from vertically oriented Apollo photographs.

The use of high-oblique photographs required an inhouse capability to rectify photographs with a 40-degree tilt and scales ranging from approximately 1:370,000 at 1:530,000 at X2 enlargement. All control data for the project were furnished by DMA. Attempts to rectify the photographs on the T-64 orthophotoscope, following initial rectification to a lunar control base on the E-4 rectifier, were unsuccessful due to the excessive tilt. Rectification on the Gestalt Photo Mapper (GPM-2) was also unsuccessful due to the amount of tilt involved and lack of sufficient contrast on the photographs necessary for automatic correlation between models. The problem of tilt may be overcome in the future when new software being formulated for the GPM-2 becomes operational, but the lack of contrast inherent in the original Apollo photographs might continue to present difficulties in electronic correlation.

Further rectification experiments are being conducted on the Wild OR-1 orthophotograph system using digital profile data provided by DMA as input. Results obtained on the OR-1 will be instrumental in determining current capabilities for rectifying high-oblique Apollo photographs to produce 1:250,000-scale lunar orthophotomaps.

Stereocombination of Landsat and aeromagnetic data

Many earth scientists use stereopairs of aerial photographs to study landforms by interpreting the third dimension of terrain relief. During fiscal year 1979, the Geological Survey took two-dimensional digital Landsat data and stereocombined it with digital topographic data to generate a Landsat stereopair. The topographic data was used to alter the horizontal location of image points across one Landsat image so that when viewed in conjunction with an unaltered Landsat image, the viewer could interpret-could "see"-the terrain relief.

A new concept is being investigated by the Survey, whereby a parameter other than topography is displayed stereoscopically as the third dimension. Vertical aerial photographs and aeromagnetic data were recorded simultaneously over an area of New Mexico. The spatial variations in the magnetic field were correlated to the Landsat image of the area and used to generate a Landsat stereopair in which the strength of the magnetic field is shown continuously in place of natural terrain elevations.

With the development of digital data bases, stereocombined graphics can be produced based on a variety of data sets. Further research is needed to determine what types of data would warrant display in stereocombined forms as opposed to conventional contour graphics.

MISSION

The Geologic Division conducts programs to assess energy and mineral resources, to identify and to predict geologic hazards, and to investigate the effects of climate. The assessments resulting from these programs are vital to planning for the wise use and management of our natural resources and to mitigating the disastrous effects from geologic hazards.

In the last several years, the Survey's responsibility in assessing the Nation's resources has increased markedly, especially in the areas of energy-oil and gas, coal, geothermal, and uranium. Large areas designated by Congress for inclusion as Wilderness Areas have required mineral assessments, and additional areas are likely to be designated in the future. Studies are being done to evaluate the energy-resource potential of offshore areas and the environmental hazards that pose problems to the development of that energy. In addition, a major program for earthquake hazard mitigation and prediction is now well underway. Geologic hazards related to nuclear reactor siting are being investigated. In support of these extremely important mission programs, extensive basic research is done continually on geologic processes and events. Basic research continues to be an important and strong part of the Division's programs and provides the capability needed to respond to emerging national problems.

The Geologic Division budget is presented to Congress under four subactivities that fulfill the above programs. A brief description of these subactivities is given below.

Land Resource Surveys supply basic data in the form of geologic, geophysical, and geochemical maps and reports. Research is conducted to predict and to delineate earthquake and volcano hazards, to identify environmental problems related to coal development and nuclear reactor siting, and to identify, to map, to report on, and to date geologic processes and historical natural events, including climatic changes.

Mineral Resource Surveys provide an assessment of the distribution, quantity, and quality of the mineral resources of the United States. During fiscal year 1979, these surveys were concentrated in Alaska, Wilderness Areas, and other public and Indian lands. Research is also conducted on the fundamental geologic processes that result in mineral formation.

Energy Resource Surveys provide assessments of the distribution, quantity, and quality of the Nation's coal, oil and gas, oil shale, uranium and thorium, and geothermal resources. Assessments of these resources are continually updated so that information is kept current.

Offshore Geologic Surveys investigate the continental margins of the United States and its territories to assess the potential mineral and energy resources and to identify environmental hazards that must be considered when siting offshore drilling platforms and pipelines. The following 10 articles describe some of the research and assessments done by the Geologic Division in fiscal year 1979. Although they reflect only a small portion of the current programs, these articles represent typical ongoing activities of the Division.

Northern Cascade Primitive Area, Wash. Malachite Lake in foreground; Monument Peak on skyline.