Assessment of elevation measuring techniques for national mapping

Abstract

This study assessed the vertical accuracy of measurement using different types of survey techniques namely LiDAR, Aerial Photogrammetry and Topographic Maps against the Ground Truth collected by RTK GPS. The study used the same geographical area for each of the land surveying techniques and was compared to elevations readings taken by RTK GPS. Measurements were taken over different types of land cover including open terrain, tall weeds and crops, brush lands and low trees, forested areas fully covered by trees, residential areas as well as land surfaces of different gradients Applying the regulations stipulated by the National Mapping Standards of United States of America and Australia, LiDAR was found to be more accurate than Aerial Photogrammetry for remapping the national maps of Trinidad and Tobago. This is because in Trinidad and Tobago, the national maps have contour lines generated at 25ft intervals and LiDAR has met the accuracy within the study area for generating contour lines at intervals up to 10ft in accordance to the American Society for Photogrammetry and Remote Sensing (ASPRS). Apart from meeting the accuracy standards required by international bodies, LiDAR would be recommended because of the very dense point cloud captured of the earth’s terrain. The datasets can be easily automated requiring a low level of manual labour. This is in contrast to Aerial Photogrammetry which requires spot heights to be manually extracted and tend to be very time consuming depend on training of the photogrammetrist.

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Garrett Seepersad
Navigation Engineer

In pursuit of knowledge to enable high precision positioning at a significantly lower cost.