complicated socio-economic objects are scarce, the relief is 
mostly homogeneous and vegetation cover is negligible. The 
noticeable lack of reliable knowledge on environmental high- 
latitudinal processes and their impact on Arctic archipelagoes 
requires, from the very beginning, complex regional monitoring, 
comprising both the entire unity of terrestrial features and wide 
terrestrial coverage. 
Limited possibilities of modern satellite remote sensing usually 
do not allow for the investigation of submarine and subterranean 
objects, and the main object of complex satellite monitoring is 
related with a particular locality, i.e. ground surface with all its 
visible natural and man-made features accessible for direct 
remote observations. Moreover, spaceborne surveying does not 
immediately allow for a comprehensive analysis of functional 
interdependencies in the high Arctic environment. One barrier to 
such investigations is the manyfold increase in the number of 
thematic studies requiring field research in situ which can be 
very problematic if it has to be carried out under severe Arctic 
conditions. The study of spatial relationships rather than 
functional interrelations between terrestrial objects falls in the 
category of topography, and in order to exactly determine the 
subject and methodology of the present studies the term 
topographic monitoring has been suggested (Sharov 1997, b). 
2.2 Topographic aspects of monitoring 
Topographic monitoring is defined here as a systematic 
topographic-geodetic survey of a concrete place, locality, region 
or separate topographic objects aimed at the detection, analysis 
and forecast of actual and potential topographic changes. The 
main tasks of topographic monitoring are accordingly formulated 
as follows: 
e determining areas and modes of topographic changes; 
e identifying topographic features that do not change or have 
remained almost unchanged throughout the period of 
observation and can serve as a tiepoint for the measurement 
of terrestrial changes; 
e forecasting future topographic changes and documentary 
representation of results. 
A flow chart explaining the logical sequence and contents of the 
principal stages of topographic monitoring is given in Figure 1. 
The ultimate aim of topographic monitoring is to provide new 
(not obligingly cartographic) reliable information on 
- the current state of a particular locality; 
- values, rates, and acceleration of topographic changes; 
- regions or separate objects undergoing extreme (maximal, 
minimal) changes; 
- topographic change forecast. 
In any remote region characterized by rather poor topographic 
knowledge, the reliable and representative results of satellite 
topographic monitoring would provide a good basis for deciding 
on the revision of available standard map series and for 
determining the required scales and intervals of topographic- 
geodetic surveys. Representative information on topographic 
changes is also important for taking administrative measures that 
may become necessary to prevent negative consequences of 
current changes. 
In general, the complement of topographic objects under 
observation depends on the working scale of monitoring and can 
be defined by analogy with the information requirements for 
topographic maps at a particular scale. In practice, dynamic and 
labile features such as glacial landforms, shorelines, 
hydrographic networks, some elements of original relief 
(stonefalls, nunataks, bars etc) and areas of pioneer vegetation 
are of special interest for satellite topographic monitoring in high 
Arctic areas. Both quantitative geometric alterations and 
qualitative changes, e.g. changes in the category of a topographic 
object or the type of natural borders, may be investigated by 
topographic monitoring. 
If typical rates V of topographic changes in Arctic region are 
supposed to be known, then principal requirements for the 
contents of topographic monitoring, such as interval, 
detailedness (spatial resolution) and accuracy can be defined 
depending on the working scale M. If remote sensing imagery is 
used directly as a base for monitoring, the linear equation 
relating a monitoring scale number M to the required image 
ground resolution A given in meters can be presented in the 
following form 
M =5000-4 . (1) 
On the other hand, spatial resolution of spaceborne image data 
must be sufficient for the detection of typical topographic 
changes in the investigated region. Hence, the following relation 
holds 
ASV-AT, (2) 
where AT denotes the time interval between observations. 
Then, the required interval can be determined as follows: 
A se A 2 (3) 
V. 5000.V 
where coefficient c = 3 + 5 depends on the task, object type and 
image data, and shows that for reliable detection, measurement 
and visual representation the size of spatial changes must not be 
smaller than several elements of the image resolution. If typical 
rates of change v=V/M are given at /:M scale and expressed in 
mm/a, then relation (3) can be transformed into the following 
expression 
AT =0.2:c/v. (4) 
Hypothetical parameters of topographic monitoring, obtained on 
the supposition that V = 10 +50 m/a, are given in Table 1. 
  
  
  
Multitemporal spatial data 
collection (surveys) 
  
  
  
Data preprocessing (calibration, 
correction, coregistration) 
  
Semantic analysis of images 
(topographic interpretation, 
identification) 
  
  
  
f 7 
y 
  
  
  
Change forecast 
  
  
Change detection, measurement, 
  
Topographic and topological 
  
  
  
  
  
  
  
  
  
  
classification modelling 
à 
Y od 
Representation of results Controlling operations 
(cartographic outputs, (ground control, quality control) 
conclusions, commands etc) Fig 1. 
  
  
  
  
  
  
Principal flow chart of topographic monitoring 
202 Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998