EXPERIENCES FROM THE 
TRANSFORMATION, CORRECTION, REVISION AND PRODUCTION 
OF TOPOGRAPHIC ORTHOPHOTO MAPS OF THE BALTIC STATES 
USING SPOT DATA 
- THE POTENTIAL OF SEMI-AUTOMATIC DATA ACQUISITION METHODS 
Dan Klang 
The Royal Institute of Technology, Department of Photogrammetry, Stockholm, Sweden 
ISPRS commission - WG IV/2 - International Mapping from Space 
KEY WORDS: SPOT, Orthoimage, Transformation, Revision, Mapping 
ABSTRACT 
After the liberation of the Baltic states the only existing maps were those produced by the old Soviet mapping authorities, except for 
the pre-war map series. The maps were erroneous and old, respectively. A topographic map serie is crucial to have for any society, 
With conventional technology based on aerial photography, the Baltic States would not have been able to obtain this basic 
information for many years. 
During a period of 2-2,5 years a new map serie is produced based on SPOT orthophotos. The maps are produced, specified with a 
new geodetic datum and a projection specific for all three Baltic states. The production procedures established in the Baltic projects, 
representing the most up-to-date technology of mapping, include GPS measurements of ground control points, satellite registrations, 
interpretation, digitizing, data base storage and digital map production. The map and data base project has also been a possibility for 
the National Surveys to restart their production organizations. 
The objective of this paper is to describe production routines and methods using SPOT data combined with other geographical 
sources to create Topographic Base Maps. The satellite data are even presented as image background in the final map product, 
Compared to traditional methods, this technique reduces both costs and production schedules without significant reduction in the 
accuracy of the interpreted features and objects. 
Due to the complexity of the projects and the fact that this paper includes production procedures in three countries, the methods 
describe the proposed solution of the map production. National experiences may result in small modifications of these general 
  
methods to optimize the process and the quality of the final data base and map products. 
1. INTRODUCTION 
During the last decade topographic mapping has experienced 
extensive changes. Digital processing has become more 
frequent and efficient, which, of course, is due to the ability to 
create databases including geographically correct positioned 
information, increased data storage capacity and reduced cost of 
equipment. Digitally stored information allows the user to 
create a flexible and specific map design of the data depending 
on the features extracted from the data base. 
The first contact between the Baltic states and SSC Satellitbild 
was established in the beginning of the 1990s. Investigations 
into how to use satellite data for environmental monitoring and 
natural resource mapping were combined with a search for 
financing possibilities. The investigations showed that the most 
urgent need was for digital topographic base maps on a scale of 
1:50,000. 
The Baltic Base Map project, unique in several ways, relies 
mostly on the use of the most recent technology in several of 
the production procedures. The tight time schedule has 
indirectly determined the layout of the projects. The objective 
was to create a "complete" data base with appurtenant printed 
maps, including a smaller number of features and objects 
compared to traditionally produced topographic maps. 
The production routines can be divided into three main parts, 
briefly described as follows: 
e Production of satellite images, which are the main source 
for the interpretation as well as, naturally, for the 
geographical position. The objective of this technology is to 
provide a radiometrical and geometrical quality that makes 
possible an optimal interpretation result. 
e Interpretation and digitalization, including "intelligent" 
coding to increase the possibility of the utilization of the 
data base. 
e Cartographic map design and printing, using the interpreted 
and digitized information in combination with a satellite 
image background. 
2. PRODUCTION ROUTINES AND METHODS 
2.1 Programming 
To optimize the use of the satellite it is possible to select sensor 
combinations, accepted viewing angles and time periods during 
the registrations over a certain area. 
The final maps include features like forest, agriculture areas, 
water and urban areas. These and other features are more easily 
interpreted from satellite data registered during the vegetation 
period using multispectral sensors than by using panchromatic 
information. In accordance with this period the multispectral 
scenes are chosen from the established archive, or programmed. 
The acquisition period starts at the beginning of May and ends 
in September-October. The registration schedule for 
panchromatic information is extended by approximately two 
months, compared to the multispectral registrations, including 
the whole snow-free season. 
No data included in the project are older than 3 years, an 
important asset when interpreting the infrastructure and the line 
information in the panchromatic scenes. 
By using registration angles less then +10° and a generalized 
DTM it is possible to achieve acceptable accuracy of the 
geometrical corrections. 
2.2 Radiometric correction 
The use of different satellites with different instruments makes 
it necessary to calibrate the information, otherwise problems 
could occur when comparing data. Calibration within the 
individual instruments is also necessary, since the sensors are 
not totally stable in time and some drift could occur in the 
registered information. 
There are small random variations in each detector inside the 
CCD (charge-coupled device) arrays. Since one detector 
registers one column in the image, "pushbroom" technique, it 18 
454 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
  
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