Mauro Caprioli 
CRITICAL COMPARISON BETWEEN DIGITAL MAP AND LASER SCANNING 
  
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V MAURO CAPRIOLI 
1 POLITECNICO DI BARI ITALY 
d DIPARTIMENTO DI VIE E TRASPORTI 
br Caprioli@dvt005.poliba.it 
es KEY WORDS: AIRBORNE LASER DATA, DTM GENERATION, ACCURACY. 
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1g ABSTRACT 
The regular GRID of Airborne LASER data and the existing maps have been imported into MODELER software 
(by Intergraph) in order to create a DTM. With this software it has been possible to analyse the data. Both the 
at Laser data and the existing cartography representation has been compared from metric point of view in order to 
he carry out the possible differences and individuate the weak point, if any. Two test areas has been selected, 
= taking in account the different characteristics of the territory. 
oF In the future, as software and hardware are going to improve, the use of LASER SCANNING DATA will be 
m more frequent in order to obtain much accuracy and a possible friendly use of this new methodology. 
ot 
hs 1. INTRODUCTION 
of The territory representation with cartographic methodology has been deeply changed in the last years by the 
introduction of new technologies. 
The ancient maps on different scale have been replaced, step by step, with different media type which contain 
he digital files related to the point localization (such as buildings corners, roads, spots heights, etc.), with the 3 
IS spatial co-ordinates and a (feature) code that permits the localization of the objects. 
on In this way the plotting is just one of the many type of the territory representation, with the limits coming out 
a from the map plane reduction. The 3D representation and visualization, eventually from different point of view, 
re of the territory and of the human objects (roads, buildings, etc.) is possible, on the contrary, using various 
T software that now are in common use on the market. 
M With this respect the metric characteristics and information of the Absolute Orientation of the air-photography 
m or of other data source (such as remote sensing, radar, laser, etc.) are given by alternative technologies instead of 
topographic survey which are more and more expensive because realized by specialists. Also for the GPS 
methodology, so helpful for the survey of a topographic net, many specialists are required. 
The Airborne Laser Scanning could be a new methodology to determine the metric information of the air- 
photography, which continue to be the most important data source, because of the not-replaceable 
\B photography quality image interpretation. 
ird On this future perspective, with this article we have analysed the accuracy of the Airborne Laser Scanning 
methodology on a building area in the City of Pavia (Italy), with the comparison of the laser data on an existing 
cartography of the same area. 
We have described all elaboration performed in order to make the data homogeneous, and consequently to 
make the two methodologies compared and to point out the differences. 
^D 2. EXISTING CARTOGRAPHY 
A) - 1:2000 Map scale 
The available cartography on 1:2.000 scale of Pavia town, developed in 1991, has been converted in digital files 
(digitizing) and updated in 1998. We can consider that the planimetric accuracy is around +/- 50 cm, and the 
altimetric one is around +/- 25 cm. 
SS B) - 1:500 Map Scale 
Also this cartography is coming out from existing maps converted on digital files with digitizing methodology; 
the spot height feature has been obtained with direct survey (levelling, etc.) on the ground and the building 
height has been drawn up with Photogrammetric methodology. So we can consider that the planimetric accuracy 
is around +/- 30 cm and the altimetric one is around +/- 15 cm. 
In order to make homogeneous the data coming out from the existing cartography (digital files) with the Laser 
data the following tasks have been performed: 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 133