The precision of areas and volumes, derived from medium- and large-scale topographical maps

Abstract

This paper is the result of a part of a comprehensive study on the quality of information which medium- and large-scale maps can provide for a great variety of purposes such as morphometric analyses, rural and urban development, engineering surveys for the planning and construction of large technical projects, etc. It all too often happens in practice that theories are developed or supported, or technical decisions are taken on the basis of information that does not warrant success by its reliability and precision, given the limits of risk. The ever-increasing use of these maps calls for a better insight as to the selection of scales, contour intervals, etc. by means of a critical assessment of the reliability and precision of the features presented in the maps in relation to the purpose of the extracted information. The aspect treated in this paper is concerned with the estimation of the precision of an area enclosed by a contourline applying the concept of the tubular confidence space of contourlines as developed in Richardus (1973), the area concerned having been surveyed by photogrammetric methods. The precision of volume is derived subsequently. A proper estimate has a direct impact on the planning of engineering works, and in many cases on payments to contarctors.