Tests were run on simulated and real block data to evaluate the comparative accuracies of bundle and independent unit block triangulation. Cases run using the ISP simulated test block were: bundles, pairs, triplets overlapping by one photograph, and triplets overlapping by two photographs with and without the perspective centers being pass points. The bundle method was superior using the data with random errors only, while the units were slightly better for the data with random plus systematic errors. Cases run using the U.S. Geological Survey, Middleburg, Va. real data test block included those run with simulated data and also quadruplets overlapping by one photograph. The horizontal accuracy results of the bundle method were essentially the same as those from units. For vertical accuracy, the bundle was slightly better in all cases except for the quadruplets, where it was slightly worse.

The U.S. Geological Survey formed a Digital Applications Team in 1977 and started development of a Digital Cartographic Applications Program. The objectives are to produce, manage, and distribute cartographic data in computer compatible form. The principal types of data are similar in content and accuracy to the categories found on the standard 1:24,000-scale 7.5-minute topographic maps. Activity is also underway to produce a national small-scale data base at 1:2,000,000 scale. The data is organized into a Digital Elevation Model (DEM) data base and a Digital Line Graph (DLG) data base and standard file formats and attribute codes have been developed. The data will become of major importance for map preparation and revision and will allow the development of geographic information systems.

A description is given of the Coastal Mapping Handbook distributed by the Government Printing Office. The handbook contains a complete but elementary description of the mapping process and includes examples of map products. Names and addresses of state and federal sources of technical assistance are also included in the handbook.

The utility of high altitude, 1:120,000-scale, color, infrared aerial photographs for inventorying inactive surface mines and assessing their environmental conditions was demonstrates for a 200 sq mile (500 km²) area in Pennsylvania. Some 60 surface mines that had been abandoned with little or no reclamation were detected using 1971, 1973, and 1975 photographs. Revegetation was the primary indicator. Through stereoscopic analysis of the photographs, each inactive mine was characterized by mining method, topographic features, erosion, mass wasting, revegetation, water quality, and visibility from roads or populous areas. Numerical values were assigned to these characteristics in order that a rating could be calculated for each mine. This rating reflected the mine's overall level of environmental disturbance or potential environmental hazard.

Aerial surveys, using camera and scanner systems, can help in collecting reliable and adequate hydrologic data over large areas in an effective time frame. Careful mission planning is an essential prerequisite to successful completion of the survey. The various considerations in regard to sensor package design and combined instrument coverage are highlighted. The solution to the problems of definition of survey area, flight planning, and path recovery in areas with inadequate or outdated topographic sheet coverage and where few details are available for precise navigation are described. This paper reflects the experience gained from the planning and execution of airborne camera or scanner missions, or both, in India. This would also have relevance in other developing countries.

Chapter Five, Map Content and Symbols, of the forthcoming ASCE manual, Manual on Map Uses, Scales, and Accuracies for Engineering and Associated Purposes, addresses the standardization of the procedures used to compile and revise maps between the scales of 20 ft/in. (1:240) and 400 ft/in. (1:4,800). Brief descriptions of the standard mapping procedures and conventions are incorporated into the chapter. Tables 1 to 8 of the chapter are concise comparisons of nine computer graphics software systems. The tables describe each system and compare the systems in terms of cost, what hardware is required, mathematical capabilities, graphic output capabilities, and what primatives are included. Tables 9 to 26 are recommended standards for the symbology to be used on larger scale engineering and associated maps.

The finite element method is used in adjusting trilateration nets. The principle is to consider the trilateration net with distances and points as a structural framework with members and nodes. The framework must be supported for structural stability according to the nature of the problem. Redundant elements are removed and initial coordinates are calculated for the nodes. Misfits are obtained as differences between measured and calculated lengths from the initial coordinates. Stiffnesses of the members are the same as the weights of the corresponding distances. All this information is introduced as input in the computer program FINITE. The output yields the displacements of the nodes in the directions of the axes of the coordinate system. It also prints out the final forces in the members. The nodal displacements are the corrections in the northings and eastings of the net points. The forces in the members divided by the corresponding weights give the corrections in the lengths of the distances.

Government mapping programs have often been cost ineffective because of the repetition of incompatible and redundant mapping efforts at the conclusion of which the resultant maps are often not available for reuse or are not applicable to other purposes. These conclusions are drawn from a critical review of a mapping program which has evolved into the development of a wetlands restriction program for the Commonwealth of Massachusetts, mandated by statute and administered by a state agency. The subject mapping program has evolved from a process of annotation directly on contact prints of aerial photographs to the production of ground-controlled orthophoto maps prepared to National Map Accuracy Standards, but the purposes of the programs have not yet been achieved. The program is at a standstill while the subject of litigation in the courts of Massachusetts and of thorough review by the Massachusetts Attorney General.

The impetus for the development of GIS technologies is derived primarily from the fact that traditional manual techniques for the derivation, organization, storage and use of spatial data are no longer sufficient to meet the demands and expectations placed on such activities. The GIS technology is a service technology used to assist spatial data management, evaluations and analyses. There are three basic approaches currently developed that organize spatial data in a format such that the computer can perform previously time-consuming analytical and display processes. These are: (1)the rectangular grid approach; (2)the fine or coarse polygon approach; and (3)the triangulated irregular network approach. There is a wide range of applications that can be supported by GIS. These can be reasonably divided into two groups: those that depend on qualitative analysis and those that depend on quantitative analysis. The GIS design requirements are much more demanding to support quantitative analyses.

The paper defines the background and current use of Geographic Information Systems (GIS). Specifically, it describes and illustrates a computer based interactive graphics GIS developed at Harvard University, called The ODYSSEY Project.

A method is described whereby longitude, latitude and azimuth can be obtained by taking sights on the sun at short timed intervals. Both rate of change of altitude with time and rate of change of bearing with altitude can be used to calculate the observer's position and the direction of the meridian. A calculator can be programmed with monthly data from the Star Almanac for Land Surveyors to correct for refraction and carry out the necessary calculations from the raw observations. No previous knowledge of position is required.

A Manual on Map Uses, Scales, and Accuracies for Engineering and Associated Purposes, in preparation by a Task Committee of the Committee on Cartographic Surveying, of the Surveying and Mapping Division of the ASCE, is nearing completion. This preparation is part of the long-range objective of the parent committee to aid engineers in obtaining maps which best fulfill their requirements. For a wide range of engineering and associated purposes, the proposed manual will: (1)Provide a means of determining appropriate scales and contour intervals, based on present and past practice; (2)present a functional method for defining map accuracies according to need; (3)furnish guidelines on the map's content and symbols required to depict graphically the details essential to its purpose; and (4)supply information on the availability of existing maps suitable for the intended purpose. This paper will present a brief report on the development of the manual, its purpose, and highlights of its content.

During the planning and design of engineering works, various uses of maps are required due to the varied levels of required information. Various agencies of the U.S. Government produce a multitude of maps, each with a specific usage intended. Lesser known, are some of the map products produced by agencies of state governments, i.e., general highway maps, geologic mapping, etc. Also available to the map user are the by-products of mapping such as aerial photography, diapositives, copy negatives, feature (and color) separates, and digital information. Hydrographic surveys are the basis of nautical chart information and copies of these surveys may be obtained on request. Highway plan sheets and railroad valuation maps provide valuable data regarding these modes of transportation. Maps useful to the petroleum industry include structure maps, base maps, and lease maps.