Sander Oude Elberink 
  
    
     
  
  
  
  
  
  
  
  
  
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> Fig. 1: Part of FLI-MAP data set; 
left: height image 0.5 meter grid hi, 
© models i € 
ods ii Fig. 2: Part of Optech data set; 
ata nn left: first pulse height image 1 meter grid resolution; center: reflectance image; right: last pulse height image. 
ential to ; 
ets from . 
lata. The system over an other urban area. This system has been mounted in an airplane, the average point density within the 
* > ^ . . . . 2 ; + 
GIS day overlapping part of two laser scanner strips is in the order of 0.7 points / m^. The system has got the advantage that it 
registers the first and the last part of a laser pulse simultaneously. 
The amount of significant classes to be extracted depends mainly on the point density, the range accuracy and the 
quality of the reflectance image. In both the FLI-MAP and the Optech data sets one can recognize objects like 
buildings, sheds and trees in the height image, and roads, grass-lands and agriculture fields in the reflectance image. In 
n of 3D the very dense FLI-MAP data set even small objects like cars, cows and lampposts are visible in the height image. 
Scanner 
kis fan 2 NORMALISED DSM 
>rformed 
from i Airborne laser scanners provide a Digital Surface Model (DSM) that not only represents the terrain surface like Digital 
action of Terrain Models (DTM), but also contains buildings and other objects like trees, which are higher than their 
9 «eim surroundings. To enable the use of thresholding techniques in the extraction of objects above the terrain surface, a 
vailable, 
al source 
lels from pouces 
d on the ius 
Peer A sheds 
Isotropic DEM e: wr 
in loci : dd roads 
erations suse 
| objects 
data will 
jons and 
rk is the DTM 
ata. The 
and also 
; of houses 
% DSM - DTM = 
Lt T Normalised DSM sheds 
1 
ur amd ann NT roads 
the last Fig. 3: Determination of the normalised DSM. 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 679