Investigating the accuracy and use of digital ortho-images (DOIS)

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As the field of photogrammetry moves to the digital domain, it is being effectively used for the production of Digital orthoimages (DOIs). DOIs have numerous advantages including its use as an excellent base layer for geographic information systems (GIS). However, a significant segment of the user community is concerned about product accuracy of DOIs. The objectives of this research include investigating the significance of the effect of varying number of Ground Controls Points (GCPs), varying grid intervals of digital elevation model (DEM) and varying scale corresponding to different pixel sizes on the planimetric accuracy of DOIs and the effect of accuracy on use. The main findings of the research revealed that a variation in the number of GCP had significant effect on the planimetric accuracy of the final DOI produced compared with the variation in DEM grid interval and variation in scale. In addition, it was clear that DOIs can be used for the purposes of most small and large scale maps. However they cannot be used at scales beyond the allowable magnification of the source scale. « Keywords: Digital, Accuracy, Analysis, Production, Photogrammetry, Aerial triangulation, Digital Terrain Model, Orthoimages, orthorectification
A Thesis Submitted to the Department of Geomatic Engineering, Kwame Nkrumah University of Science and Technology In partial fulfillment of the requirements for the Degree Master of Science.