TES AM SE 
PROJECT SWISSPHOTO - 
DIGITAL ORTHOPHOTOS FOR THE ENTIRE AREA OF SWITZERLAND 
Thomas Kersten, William O’Sullivan 
swissair Photo+Surveys Ltd. 
Dorfstr. 53, CH - 8105 Regensdorf-Watt, Switzerland 
Phone +41 1 871 22 22, Fax +41 1 871 22 00 
e-mail: [thomas kersten, willi.osullivan]@srpv.ch 
Intercommission Working Group II/III 
KEYWORDS: Acquisition, aerial, digital, DTM, automatic orthophoto generation 
ABSTRACT 
Digital orthophotos are an essential and up-to-date basis for various applications in geographical information systems, 
which can fulfill the significantly increasing need for up-to-date, accurate, fast acquired, reasonable and blanket cover- 
age 3-D data and maps in various scales for environmental planning and monitoring, and resource management. 
In this paper, we introduce the project SWISSPHOTO, which was established in 1995 to provide digital image data, 
Digital Terrain Models (DTMs), and Digital Orthophotos (DOPs) covering the entire area of Switzerland (42,000 km?) 
as standard products for a various number of applications and for many users. The production flow and some technical 
specifications of the project are presented. Advantages and reasons for the increasing significance of orthophotos are 
discussed. The versatility and flexibility of digital orthophotos as an integrated basis of a GIS is shown in this paper with 
many examples for the use of orthophotos in different applications. 
1. INTRODUCTION 
The development in computer technology and graphical 
data processing, and the increasing availability of high 
quality digital data have led to new forms and ways of 
data processing and management in governmental of- 
fices and in the private economic sector. This caused an 
increasing need for digital topographical information, 
which is necessary as the basic data level for spatial 
and thematical digital data processing in geographical 
information systems (GIS). The need for up-to-date, 
accurate, fast acquired, reasonable and blanket cover- 
age 3-D data and maps in various scales for environ- 
mental planning and monitoring, and for management 
of resources is significantly increasing. Spatial data and 
high quality maps are required for various applications 
in planning offices, in many surveying service compa- 
nies, departments of governmental offices (state, can- 
tons, communities), in communication, transport and 
traffic offices, in energy supply companies, and many 
other fields such as research and tourism. Therefore 
digital orthophotos derived from satellite or aerial 
images are an ideal solution to provide topographical 
data for many users and applications. The georeferen- 
cing of the orthophotos guarantees later the common 
use of several different data sets in the GIS. For the 
following reasons the significance of digital orthopho- 
tos is increasing. (Gruen et al., 1994): 
* Using satellite or aerial images blanket coverage 
digital data is easily available. 
186 
* High quality scanners allow the digitisation of ana- 
log images and other data. 
* Digital terrain models (DTMs) as a basis for digital 
orthophoto generation is available in different qua- 
lity levels using various modern data acquisition 
methods, e.g. digital image correlation, laser- 
scanning, etc. 
« Necessary control point information can be acquired 
by GPS in an accurate, fast and reasonable way. 
Computers of high performance and increased disk 
storage capacity are available today at a reasonable 
cost. 
e Commercial software for orthophoto generation is 
available from a variety of vendors. 
» Digital cartography uses increasingly digital ortho- 
photos for map restitution. 
* Swiss official approved surveying uses digital ortho- 
photos for the restitution of ground coverage outside 
urban areas and for the verfication of the large scale 
maps. 
» Digital orthophotos (DOPs) are an important and up- 
to-date information level in GIS. 
» With reasonable visualisation software on PC's, 
digital orthophotos will gain entry into the public 
market. 
The building of a GIS plays more and more an im- 
portant role in various applications. Therefore, the 
individual factors of costs must be correctly estimated 
in the building phase of a GIS. In the era of the high 
performance and low cost computers, the hardware 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996 
cos 
cos 
of 
img 
up- 
dat: 
enti 
var 
Phc 
pro 
As 
in c 
ner: 
tos 
e 
pr Áo ra eh M D^ rM 
For 
date 
pare 
area 
higt 
va/I 
de a 
desk 
proc 
on 
betv 
phot 
suril 
auto 
Hae 
be d 
stere 
as a 
deri: 
acqu 
map 
digit 
(Lin 
gene 
tic g 
relat 
relat 
for e 
metr 
the c 
rity