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ASPECTS OF THE DSM PRODUCTION WITH HIGH RESOLUTION IMAGES 
C. Lemaire 
INPHO GmbH, 70174 Stuttgart, Germany - charles.lemaire@inpho.de 
Commission IV, WG IV/9 
KEY WORDS: Photogrammetry, High resolution, DEM/DTM, Production, Matching, Precision 
ABSTRACT: 
This paper deals with the production of digital surface models (DSM) from high resolution images. The paper explains why the 
quality of the dense DSM depends on the quality of input data and data compilation. The INPHO GmbH software MATCH-T DSM 
has been redesigned to produce very dense DSM data. The most important improvement was the introduction of sequential multi 
image matching. The point extraction is no longer based on static models, but on computation units. Each computation unit in 
MATCH-T DSM chooses the best suited image pairs. Each image pair delivers a point cloud, the combined point clouds are filtered 
by a robust analysis. The precision and the completeness of the MATCH-T DSM from high resolution images is analyzed in two 
case studies. 
RESUME: 
Cet article a pour sujet la production de modèles numériques de surface (MNS) à partir d’images aériennes à haute résolution. 
L’article montre pourquoi la qualité du MNS dense dépend fortement de la qualité des données d’entrée et du mode d’acquisition. 
Le logiciel MATCH-T DSM développé par INPHO GmbH a été reconçu pour pouvoir produire des MNS très denses. Pour ce faire, 
une méthode d’autocorrélation séquentielle a été développée. L’extraction n’est plus effectuée par une compilation de modèles 
stéréoscopiques statiques ; pour chaque unité d’extraction, MATCH-T DSM choisit les paires d’images les plus appropriées ; chaque 
paire d’images fournit un nuage de points qui sont ensuite filtrés à l’aide d’une analyse statistique robuste. La précision et la 
complétude du MNS extrait avec MATCH-T DSM sont évaluées dans deux études. 
1. INTRODUCTION 
Matching algorithms are seeing a renaissance. The cause of this 
resurgence is the increasing demand of accurate and low price 
DSMs. The new matching generation can hardly be compared 
to the last one. Because the current technologies offer much 
more computing power and the introduction of digital cameras 
has revolutionized the traditional photogrammetric project scale 
and overlap. This article introduces requirements for the 
production of very dense DSMs from high resolution images. In 
this paper high resolution images are aerial images with a 
resolution higher 20 cm. The article presents changes to the 
matching technologies to achieve high quality results for these 
new challenges, and analyses of the quality of the DSM, 
introduced with the new MATCH-T DSM software. 
INPUT AND DATA COMPILATION 
The quality of a dense DSM depends on the quality of input 
data and data compilation. The input data are images, 
orientations and camera calibration data. Additionally, results 
will be influenced by the stability of the hardware and flight 
planning. Since MATCH-T DSM can correlate with sub-pixel 
accuracy, it is essential to use a digital metric camera with 
Overlap 
The traditional photogrammetric workflow is based on 60% 
forward and 30% side overlap. This standard overlap creates 
occlusion areas and reduces the redundancy of image 
information. Overlaps of 60/60 or 80/30 allow just enough 
redundancy for the DSM extraction as 4 images cover any open 
area. Only very high overlap configurations like 80/60 or 90/70 
reduce significantly the occlusion areas in wooded or city areas. 
Most of the new digital large frame cameras have a non-square 
format, hence the viewing angles along the line of flight and 
across the line of flight differ. The longer side which has the 
larger angle of view exhibits more occlusions than the short 
side. Thus the camera should be mounted in a way that the 
smaller side of the sensor is perpendicular to the flight direction. 
The high overlap allows a higher probability of successful 
matches, as the features are very similar. On the other hand the 
base line is smaller so the height accuracy is lower. That means 
that the extraction needs both: Models with high overlap in 
order to minimise the occlusion areas, and models with large 
base lines to get better height accuracy. Hence the DSM quality 
has two facets height precision and completeness.