Effect of Digital Elevation Model Mesh Size on Geomorphic Indices: A Case Study of the Ivaí River Watershed - State of Paraná, Brazil

Abstract

Abstract:Geomorphometry is the science of quantitative description of land surface morphology by the mean of geomorphic indices extracted from Digital Elevation Models (DEMs). The analysis of these indices is the first and most common procedure performed in several geoscience-related subjects. This study aims to assess the impact of mesh size degradation on different local and regional geomorphic indices extracted for GDEM and TOPODATA DEMs. Thus, these DEMs, having a mesh size of 30 m, were subsampled to 60, 120 and 240 m and then geomorphic indices were calculated using the full resolution DEM and the subsampled ones. Depending on their behavior, these indices are then classified into stable and unstable. The results show that the most affected indices are slope and hydrographic indices such as Strahler order, stream sinuosity and fractal dimension and watershed perimeter, whereas elevation remains stable. It also shows that the effect depends on the presence of the canopy and geological structures in the studied area.Keywords: Geomorphic indices; Digital Elevation Model; Mesh Size; Scale. Resumo:A geomorfometria é a ciência da descrição quantitativa da morfologia da superfície terrestre por meio de índices geomórficos extraídos de Modelos Digitais de Elevação (MDEs). A análise destes índices é um dos primeiros e mais comuns procedimentos executados em estudos relacionados a

Multicriteria Evaluation of the Potential of P-Band Airborne Radar Dems for 3d Characterisation of Hydrography in Tropical Forests

“…The resampling period, i.e., the scale at which the relief is modelled, has an impact on slope accuracy (Polidori and Simonetto, 2014) and therefore on the respect of hydrographic shapes. Therefore, the hydrographic indicators based on slope are unstable when the scale is changed (Santos et al, 2017).…”

Digital Elevation Model Quality Assessment Methods: A Critical Review

“…This approach is relevant to evaluate the quality of a DEM in terms of shape rendering, for which external quality assessment is less straightforward. Indeed, the comparison of a terrain shape as modelled in the evaluated DEM with regards to a reference dataset is limited by the difficulty of defining a suitable metric, and by the fact that height derivatives (slope, aspect, curvature) and therefore shapes are not stable with regards to scale, while elevation is stable [109][110][111], as discussed below in Section 6. Therefore, the comparison of two DEMs, which may not necessarily have the same native mesh size, may bring some information on elevation accuracy, but probably not on slope accuracy or shape realism.…”

“…In other words, one may have to compare indices in DEMs of different scales, i.e., different resolutions. It should be considered that some indices are unstable when changing scale, while others remain stable [109][110][111]191]. Many studies about the impact of the mesh size on geomorphological and hydrographic indices lead to the expected result that increasing the mesh size has a smoothing effect on the DEM [192][193][194][195][196][197][198].…”

“…The problem is that the area is stable with regard to scale but the perimeter is not [200], so that the Gravelius index is meaningless if the DEM scale (i.e., mesh size in practice) is not specified, whatever the DEM quality. Santos et al [111] proposed a classification in which stable vs unstable hydrographic indicators are identified. If we consider the quality criteria defined in Section 4, these examples suggest that mesh size transformation (like any form of resampling) has more impact on the landform modelling than on elevation values.…”

Avaliação de parâmetros geomorfométricos derivados de modelos altimétricos de diferentes fontes e resoluções: estudo de caso da bacia hidrográfica do córrego Lajeado, Campo Grande, MS

“…Considerando o LA, as bases SRTM e AP superestimaram o perímetro da BH em 13,2% e 20,6%, respectivamente. O mesmo foi detectado por Santos et al (2017) em trabalho realizado na BH do rio Ivaí, no estado do Paraná. O desvio padrão entre os valores das três bases cartográficas analisadas foi de 7,07.…”