Automatic peaks extraction from Normalized Digital Surface Model (NDSM) 
S.A.M.HASHEMI 
M.Sc., Remote Sensing Department 
National Geographic Organization of Iran (N.G.O) 
P.O.BOX. 16765/3358 Tehran-Iran 
TEL: (98)-21-8840-1128 FAX (98)-21-8841-2559 
E-mail: Ar_mohammadi_hashemi@yahoo.com 
KEY WORDS: Remote Sensing, DEM ,Peaks, Photogrammetry,NSDM,Morphology 
ABSTRACT: 
Automatically extraction of peaks from 3D Digital models such as Digital Elevation model 
(DEM),Digital surface model (DSM) and Normalized Digital surface model (NDSM) is as 
important as image comprehension in Remote Sensing and Photogrammetry.Especially in urban 
areas, structures are playing a great role and methods have been used for extracting them are very 
useful for the mapping process of urban programming and Geo-spatial information system. So 
extraction of peaks from 3D Digital models in order to automatically extraction of objects is an 
important topic.Considering the importance and usage expansion, this title has been studied in 
Remote Sensing and Photogrammetry during the last few years. Digital models can be acquired by 
automatic image matching algorithms applying stereo high-resolution satellite imagery or can be 
directly captured by airborne laser scanning system.Lately,using Remote Sensing and 
Photogrammetric methods,we have reached a new horizon and modem methods about extraction of 
peaks from digital models in order to obtain different goals such as 3D city models tele 
communication industry, assessment of air pollution in different areas of the city, control analysis, 
navigation and landscape planning,etc.In this article peaks are automatically extracting from NDSM 
by means of a morphological surface reconstruction algorithm. 
1. INTRODUCTION 
NDSM is a type of raster GIS layer which 
represents a regular arrangement of locations 
and each cell has a value corresponding to its 
elevation.The peak point in the 3D Digital 
models is a pixel which have the largest value 
regard to the value of around pixels.For this 
purpose,the morphological reconstruction 
method is used in order to specifying peaks in 
digital elevation models. 
2.Preparing DATA include 
DTM,DSM,NDSM 
The case study is located near of tehran and in 
order to generation of digital terrain model 
(DTM) and digital surface model (DSM), we 
use digital map in 1:500 ratio scale. 
In this map there are two kind of height points, 
one of them is related to earth topography and 
another hight points is belong to artificial 
elevation features such as buildings .According 
to this issue, Preparing DTM is based on height 
points of streets and Preparing DSM is based on 
sum points of streets and building roofs. 
Because the NDSM represented the absolute 
elevation of artificial elevation features regard 
to the earth, for preparing of NDSM the DTM 
should be subtracted from DSM. 
So we have; 
NDSM=DSM-DTM (1) 
Where; 
DTM is Digital Terrain Model 
DSM is Digital Surface Model 
NDSM is Normalized Digital Surface Model 
calculations of interpolation operations in order 
to preparing digital models were performed by 
help of Arcview GIS software that has proper 
capabilities for these operations. 
The method of interpolation to preparing DTM 
and DSM is based on Inverse distance weighted 
interpolation.