Abstract
Improving the accuracy of digital elevation is essential for reducing hydro-topographic derivation errors pertaining to, e.g., flow direction, basin borders, channel networks, depressions, flood forecasting, and soil drainage. This article demonstrates how a gain in this accuracy is improved through digital elevation model (DEM) fusion, and using LiDAR-derived elevation layers for conformance testing and validation. This demonstration is done for the Province of New Brunswick (NB, Canada), using five province-wide DEM sources (SRTM 90 m; SRTM 30 m; ASTER 30 m; CDED 22 m; NB-DEM 10 m) and a five-stage process that guides the re-projection of these DEMs while minimizing their elevational differences relative to LiDAR-captured bare-earth DEMs, through calibration and validation. This effort decreased the resulting non-LiDAR to LiDAR elevation differences by a factor of two, reduced the minimum distance conformance between the non-LiDAR and LiDAR-derived flow channels to ± 10 m at 8.5 times out of 10, and dropped the non-LiDAR wet-area percentages of false positives from 59% to 49%, and of false negatives from 14% to 7%. While these reductions are modest, they are nevertheless not only consistent with already existing hydrographic data layers informing about stream and wet-area locations, they also extend these data layers across the province by comprehensively locating previously unmapped flow channels and wet areas.
Highlights
This demonstration is done for the Province of New Brunswick (NB, Canada), using five province-wide digital elevation model (DEM) sources (SRTM 90 m; SRTM 30 m; ASTER 30 m; CDED 22 m; New Brunswick DEM (NB-DEM) 10 m) and a five-stage process that guides the re-projection of these DEMs while minimizing their elevational differences relative to Light Detection and Ranging (LiDAR)-captured bareearth DEMs, through calibration and validation
Across the LiDAR-DEM coverages, the differences tend to be largest along forested ridges and valleys, and smallest on open areas
Negative SRTM and ASTER elevation differences relative to the LiDAR-DEM occur along valleys, shores, and forest edges, undoubtedly due to the differences in resolution (1m versus 30 and 90 m)
Summary
DEMs are used for spatial visualization and modeling of topographic, geomorphologic, and hydrological properties (e.g., slopes, soil erosion, basin borders, stream and river networks, and stream discharge) [3] [4] [5] [6] In this regard, DEM elevation accuracies and resolutions vary based on differences in mode of elevation capture, processing, point-to-point interpolations, and timing of capture [7] [8] [9] [10] [11]. In terms of acquisition and availability, DEMs of varying origins are becoming freely accessible [8] [10] [15]-[23] Increasingly available are Light Detection and Ranging (LiDAR) DEMs generated from point-cloud data through air-borne laser-light scanning and pulse return classification [24]
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