Accuracy Evaluation of Digital Photogrammetric Projects

Abstract

In spite of the development and digital replacement of the conventional techniques, there is a need for evaluating and assessing photogrammetric mapping projects, to see if they conform to specifications. In order to develop infrastructure and improve services and utilities, Khartoum State (Sudan) signed a contract in (2010) to cover the state by large scale topographic maps. Digital photogrammetric methods and techniques were planned to be used in this project. The planned project was divided into two parts; the first part covers the centre of the state by 1:5000 photographic coverage to produce maps at scale 1:1000, while the second part, cover the rural areas of the state by 1:20000 photographic scale coverage to produce maps at scale 1:10000. Technical specifications and criteria of this photogrammetric project were suggested by a high technical committee. The output of this project, including photographic coverage and the maps, were not subject to evaluation and assessment because of the absence of supervision. This research work is oriented to make some sort of technical evaluation and assessment of this project. Camera specifications, flying height, scale of the photography, accuracy of vector mapsproduced and other points were taken into account. Two sets of measurements and tests were carried out, for each part of the project. The laid specifications for the project and samples of the executed project were the refrain data. A number of ground points were observed by Differential Global Positioning System (DGPS),with their coordinates based on Universal Transverse Mercator (UTM) projection, at zone 36 north and the World Geodetic System 1984 (WGS84) datum. The Leica Photogrammetric Set (LPS), included in Erdas Imagine package, was used. The results obtained showed that, the used camera, photographic coverage in centre of the state project, and the produced line maps are all in disagreement with the specifications, but it is satisfied with the specifications of the rural area of the state.