THE CONTRIBUTION OF INFORMATION THEORY TO DEVELOPMENT OF MAPPING 
THEORY OF DIGITIZED AIRPHOTOS 
( Northwest University, China, Zhang Renlin ) 
KEY WORDS: Photogrammetry, Information theory, Digital mapping, Sampling theorem 
ABSTRACT ; 
Information theory is one of the contemporary scientific theories that 
is of great significance during the photogrammetry, It is exactly due 
to the application of many views from Information theory that promotes 
going deep into research of digital photogrammetric methodology and 
lays a theoretical basis guiding photogrammetry from an engineering 
technology mainly based on the optical and mechanical instruments to 
an information technique using computer as 
the key equipment. There 
are several examples demonstrating the practical application of Infor- 
mation theory in photogrammetry in recent years, including measurement 
of digital image information, data interpolation, data compression and 
communication in digital mapping of airphotos etc. 
1. INTRODUCTION 
Digital image processing is a technology to handle 
the digitized imagery which is widely used in re- 
mote sensing, Because the sensors on satellite 
probe the spectral information of surface features 
by means of the automatic scan, transmit the elec- 
tromagnetic signals through communication channel 
and record them in digital form on the magnetic 
media, it is most suitable for computer manipula- 
tion. Besides, the satellites transit over the 
same area periodically during their orbiting, 
hence the data volume returned to ground from aer- 
ospace is of a huge amount that there are not 
other alternative facilities to treat the volumi- 
nous information in time except for computers. 
The aerial photographs with the perspective geo- 
metry taken by a camera are the primitive infor- 
mation source for photogrammetry at present, On 
the airphotos there are recorded the characteris- 
tics of the spectral intensity between the visual 
and near infrared bands (0.4 -- 1.14) which ground 
objects viewed by the camera reflect at the moment 
of exposure, However, what has been formed on the 
films sensitive to light is the two-dimensional 
images with the continuous variation of tone wi- 
thin a constant frame. It is not possible of com- 
pater processing directly before the conversion 
of airphoto image from analogous data to digital 
ones, lmage processing systems in the early time 
were of bulk and sophisticated equipment with a 
higher cost, Mapping through photogrammetry was 
implemented mostly by the optical and mechanical 
instruments, Recently owing to the emergence of 
the portable devices for digital record and the 
microcomputers with satisfactory performace as 
well as dramatic cutdown of the prices it be- 
comes most prospercus development direction to 
digitize the airphoto imagery for the automatic 
process in computers. 
The aerial imagery plays a role of the geogra- 
rhic information carrier. The manipulation of 
image information includes the procedures from 
the simple visual interpretation to the quanti- 
tative and qualitative analyses using the ari- 
thmetic programs based on the rigorous mathema- 
tic models. It is involved to carry and handle 
the image data in the whole technological pro- 
cens of digital mapping. As Information theory 
is a subject which applies the contemporary 
statistics to research into data communication 
with high efficiency 8nd reliability, it cer- 
tainly has an undoubted significance to guide 
430 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996 
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