Abstract

The correct representation of the topography of terrain is an important requirement to generate photogrammetric products such as orthoimages and maps from high-resolution (HR) or very high-resolution (VHR) satellite datasets. The refining of the digital elevation model (DEM) for the generation of an orthoimage is a vital step with a direct effect on the final accuracy achieved in the orthoimages. The refined DEM has potential applications in various domains of earth sciences such as geomorphological analysis, flood inundation mapping, hydrological analysis, large-scale mapping in an urban environment, etc., impacting the resulting output accuracy. Manual editing is done in the presented study for the automatically generated DEM from IKONOS data consequent to the satellite triangulation with a root mean square error (RMSE) of 0.46, using the rational function model (RFM) and an optimal number of ground control points (GCPs). The RFM includes the rational polynomial coefficients (RPCs) to build the relation between image space and ground space. The automatically generated DEM initially represents the digital surface model (DSM), which is used to generate a digital terrain model (DTM) in this study for improving orthoimages for an area of approximately 100 km2. DSM frequently has errors due to mass points in hanging (floating) or digging, which need correction while generating DTM. The DTM assists in the removal of the geometric effects (errors) of ground relief present in the DEM (i.e., DSM here) while generating the orthoimages and thus improves the quality of orthoimages, especially in areas such as Dehradun that have highly undulating terrain with a large number of natural drainages. The difference image of reference, i.e., edited IKONOS DEM (now representing DTM) and automatically generated IKONOS DEM, i.e., DSM, has a mean difference of 1.421 m. The difference DEM (dDEM) for the reference IKONOS DEM and generated Cartosat-1 DEM at a 10 m posting interval (referred to as Carto10 DEM) results in a mean difference of 8.74 m.

Highlights

  • Digital Elevation Model (DEM) is the digital geometrical representation of elevation at a place, either in raster or vector form with regular or irregularly distributed points

  • The editing of a digital elevation model is an important step in the production of an accurate topography for a region

  • The present study aims to demonstrate the problems and quality assessment of the automatically generated DEMs, which are digital surface model (DSM) generated as the primary product from the initial photogrammetric solutions

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Summary

Introduction

Digital Elevation Model (DEM) is the digital geometrical representation of elevation at a place (terrain), either in raster or vector form with regular or irregularly distributed points. DEM is often used as a generic term for elevation at a pixel and can refer to DSM and DTM as per the context or application [1]–[4]. The editing of a digital elevation model is an important step in the production of an accurate topography for a region. Several automatic procedures have been developed over time, they are not able to match the manually corrected DEMs. The disadvantage of manual corrections on the other hand includes the requirement of the trained work-force, cost, and high-end photogrammetric systems besides time. For important tasks and study areas, still, the manual corrections are the best option for achieving an accurate topography using Photogrammetric techniques, which have the potential to affect the required application positively and improve results

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