A framework for generating high quality digital elevation models in urban areas

2008 ◽  
Author(s):  
Ahmed F. Elaksher
Keyword(s):  
Urban Areas ◽  
Digital Elevation Models ◽  
High Quality ◽  
Digital Elevation

A new approach for dealing with depressions in digital elevation models when calculating flow accumulation values

2010 ◽  
Vol 34 (6) ◽  
pp. 781-809 ◽  
Author(s):  
Neil Arnold
Keyword(s):  
Digital Elevation Models ◽  
Physical Geography ◽  
Main Flow ◽  
High Quality ◽  
Common Procedure ◽  
New Approach ◽  
Flow Accumulation ◽  
Digital Elevation ◽  
Fine Spatial Resolution ◽  
Very High

Calculation of flow accumulation (also known as upstream area) matrices from digital elevation models (DEMs) is a very common procedure in hydrological studies, and also has been used in other disciplines within physical geography, such as glaciology. A problem with such calculations has always been the presence of closed depressions in DEMs; flow is directed towards such areas, but then cannot ‘escape’. In many implementations of flow accumulation algorithms such depressions have been removed from the DEM with some form of pre-processing algorithm which typically transform depressions into flat areas, across which area can then be routed. This approach effectively assumes that all depressions in a DEM are therefore artifacts, and not true features within the landscape. The proliferation of very high quality, high precision, and fine spatial resolution DEMs in recent years means that such an assumption is increasingly difficult to support. In this paper, some of the main flow accumulation algorithms and some existing techniques for dealing with closed depressions in DEMs are reviewed. A new algorithm is presented which assumes that such depressions are real features in the landscape, and which allows them to ‘fill’ and then ‘overflow’ into downstream areas within the DEM. Examples with a synthetic and two real DEMs suggest that, at least in these cases, the assumption that depressions are real is justified. These results also suggest that determining the size distribution for depressions within a DEM could form the basis for identifying whether artifact depressions are a problem in individual DEMs.

scholarly journals Metric Accuracy of Digital Elevation Models from WorldView-3 Stereo-Pairs in Urban Areas

2019 ◽  
Vol 11 (7) ◽  
pp. 878 ◽  
Author(s):  
Emanuele Mandanici ◽  
Valentina A. Girelli ◽  
Luca Poluzzi
Keyword(s):  
Urban Areas ◽  
Digital Elevation Models ◽  
Technical Note ◽  
Aerial Images ◽  
Average Error ◽  
Open Spaces ◽  
Urban Structures ◽  
Digital Elevation ◽  
New Applications ◽  
The City

WorldView-3 satellite is providing images with an unprecedented combination of high spatial and spectral resolution. The stereo capabilities and the very high resolution of the panchromatic band (0.31 m) have been fostering new applications in urban areas, where the complexity of the morphology requires a higher level of detail. The present technical note aims to test the accuracy of digital elevation models that can be obtained by WorldView-3 stereo-pairs in these particular contexts, with an operational state-of-the-art algorithm. Validation is performed using check points and existing models of the area (from LiDAR data and oblique aerial images). The experiments, conducted over the city of Bologna (Italy) with six images, proved that roof surfaces and open spaces can be reconstructed with an average error of 1–2 pixels, but severe discrepancies frequently occur in narrow roads and urban canyons (up to several metres in average). The level of completeness achievable with only one pair is extremely variable (ranging from 50% to 90%), due to the combined effect of the geometry of acquisition and the specific urban texture. Better results can be obtained by using more than one pair. Furthermore, smaller convergence angles can be beneficial for the reconstruction of specific urban structures, such as soaring towers.

scholarly journals BUILT UP CHANGE DETECTION BASED ON STRUCTURAL CLASSIFICATION OF DIGITAL ELEVATION MODELS

2019 ◽  
Vol XLII-4/W18 ◽  
pp. 493-496
Author(s):  
S. Hosseini ◽  
F. Tabib Mahmoudi ◽  
A. Aboutalebi
Keyword(s):  
Change Detection ◽  
Urban Areas ◽  
Digital Elevation Models ◽  
Three Dimensional ◽  
Detection Methods ◽  
Remotely Sensed Data ◽  
Structural Classification ◽  
Digital Elevation ◽  
Multi Temporal

Abstract. Multi temporal changes in built up areas are mainly caused by natural disasters (such as floods and earthquakes) or urban sprawl. Detecting these changes which consist of construction, destruction and renovation of buildings can play an important role in updating three dimensional city models and making the right decisions for urban management. Generally, change detection methods based on multi temporal remotely sensed data can be divided into 2D and 3D categories. Three dimensional change detection methods are suitable for identifying the changes of three dimensional objects such as buildings and their results are more close to reality. The objective of this study is to provide an effective method for 3D change detection of buildings in urban areas based on Digital Elevation Models (DEM). The proposed method in this paper consists of three main steps; 1) generating the normalized DSM for two epochs, 2) performing segmentation and structural classification of image segments in order to generate multi temporal classification maps, 3) producing the change maps. The ability of the proposed algorithm is evaluated in a rapid developing urban area in Tehran, Iran in a 9-years interval. The obtained results represent that the ground and bare soil decrease for about −1.37% and low-rise buildings also decrease for about −9.7%. Moreover, the class of high-rise buildings increases for about +16.4% which conforms making new constructions in addition to renovation of low-rise buildings.

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