A design of contour generation for topographic maps with adaptive DEM smoothing

Abstract

Due to digitalization and rapid development of collection techniques for elevation data, the emphasis of users' needs for elevation contours has moved from needs of accurate elevation assessment towards needs of perception of landforms. This article introduces a design approach that considers the changed need, and a solution for accordingly generating contours for topographic maps from digital elevation models (DEMs). The solution builds upon comprehensively modifying and blending complete DEMs in order to make the generation procedure understandable for the map readers and to facilitate the readers' reliable interpretation of contours throughout the depicted terrain. The core of the solution is blending lightly and strongly smoothed DEMs according to the Topographic Position Index (TPI) that measures local deviation from surrounding variations of elevations. The solution is built to continuously consider the requirements for different levels of smoothing in areas of uniformly varying and locally deviating relief. An initial case study for typical and challenging Finnish terrains is described and success of the solution is qualitatively evaluated based on the resulting contours. Eventually, limitations of the solution as well as further evaluation and refinement needs are outlined with an intention to prepare the presented contour generation procedure for production. RÉSUMÉEn raison de la numérisation et du développement rapide des techniques de collecte de données d'élévation, la priorité des besoins utilisateurs en matière de courbes de niveaux a évolué d'un besoin en vérification de la précision de l'altitude vers le fait de pouvoir percevoir les formes du terrain. Ce papier présente une approche conceptuelle qui considère ce changement de besoin ainsi qu'une solution pour générer des courbes de niveaux pour des cartes topographiques à partir de modèles numériques de terrain (MNT). La solution est construite sur une modification complète et une fusion de MNTs afin de rendre la procédure compréhensible pour le lecteur de carte pour faciliter l'interprétation fiable des courbes de niveau par le lecteur sur tout ARTICLE HISTORY

Contour Lines Generation in Karstic Plateaus for Topographic Maps

“…The consistency with water bodies, rivers or lakes is also a key issue for relief rendering (Gaffuri, 2007), and the algorithm developed at the US Geological Survey detected the areas where contour lines needed to be consistent with water bodies (Tyler & Greenlee, 2012). Regarding the transformation of the DTM, two main methods were proposed: an elastic deformation (Jaara et al, 2011) and smoothing (Rosenkranz et al 2012;Kettunen et al, 2017). Sometimes, the contour lines are also refined after processing the DTM and deriving the contours (Rosenkranz et al 2012;Tyler & Greenlee, 2012).…”

“…In order to draw readable contour lines, the original DTM needs to be smoothed. That for we used the method described by Kettunen et al (2017). The method derives two gaussian smoothings on the initial DTM (DTM1 with a light smoothing, and DTM2 with a strong smoothing).…”

“…Past research on mountain cartography proposed automated processes to draw contour lines as close as possible to the ones drawn by cartographers (e.g. Jaara et al, 2011;Kettunen et al, 2017). However, these automated processes do not perform well on very specific terrain morphologies, for instance karstic plateaus full of small sinkholes ( Figure 1).…”

“…Following the same paradigm as the most advanced research on contour line derivation, i.e. adapting the process to the terrain morphology (Kettunen et al, 2017), there is a clear need for a specific process to improve the contour line derivation from a DTM in this specific kind of regions. This proposes such a specific process that was experimented on the karstic plateaus of the Jura Mountains in France.…”

Multirotor UAV-Based Photogrammetric Mapping for Road Design

“…The other factor is weather conditions and land ownership issue during conducting the land survey. The long road alignment might cause a lot of errors and it might have problem to merge the data at the end [4]. The other method used to capture topography information is Light Detection and Ranging (LiDAR).…”