The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
Some basic GIS functions 
Essentially, GIS provides a means of taking many different 
kinds of information, processing it into compatible data sets, 
combining it, querying and displaying the results on a map. 
Some standard GIS capabilities include: 
• Integrating maps based on different scales, map projections, 
or legends; 
• Changing of scale, projections, legend, annotations, etc.; 
• Overlaying different types of maps of a particular area to 
make a new map that combines the attributes of the 
individual maps. For example, a vegetation map could be 
overlaid on a soil map, as shown in the figure above. This 
in turn could be overlaid on a map showing length of 
growing season, thereby producing a land suitability map 
for a given crop; 
• Generating buffer or proximity zones around lines or 
polygons on a map. This technique is used to find areas 
within a given distance from roads, rivers, etc., or from 
certain thematic conditions. These buffer zones can in turn 
be used as another layer in overlay operations; 
• Querying spatial and attribute databases. 
Satellite Remote Sensing 
Satellite imagery in digital format allows for the acquisition of 
environmental data and land occupation patterns and features 
over large areas. Sensors in satellites record multispectral data 
from different wave bands in digital format. Different features 
of the terrain reflect differently in each waveband, allowing for 
their recognition in the images. The digital image is fed into the 
computer, where it is stored. The digital images can then be 
displayed and further processed to extract the desired 
information. They may also be integrated with other types of 
data and information within a GIS. 
The information found within a digital image is contained in a 
grid constructed of spatial units called pixels. Each pixel 
number is related to color intensity and brightness. The main 
limitations of satellite images are cloud cover (Earth Resources 
Satellites pass over the tropical areas early in the morning, a 
period when clouds and mist are most prevalent) and resolution. 
Even with the best resolution available (pixels < 30 m), it is not 
possible to see houses, to adequately classify some types of 
agricultural practice, or to localize some breeding sites. Some of 
these problems may be circumvented using satellite navigation 
receivers. 
By using the data from the different wave bands, it is possible to 
identify and track environmental characteristics. Vegetation, 
land-use patterns, surface waters, quality and humidity of the 
soil, roads, built-up areas, and climatic changes may all be 
monitored by satellite. 
Satellite Navigation System (SNS) 
The satellite navigation system (SNS) was originally designed 
to enable a user to obtain an instantaneous three-dimensional 
position, anywhere on the earth, at any time, under any weather 
condition. Clock information in satellites is emitted by radio 
wave. 
The difference between the time when a message is sent and the 
time when the message is received allows for the calculation of 
the distance between the receiver and the satellites. Since the 
orbits of the satellites are known, exact positions can easily be 
calculated. 
The SNS can be used in a number of ways to calculate absolute 
and relative positions with varying degrees of accuracy. The 
complete system consists of 24 satellites that are distributed in 
such a way that an adequate number of satellites is available for 
positioning at any given time. 
When associated with a GIS, a SNS receiver is a powerful 
mapping tool. It can provide quick and accurate positioning of 
terrain features and dynamic mapping. The data received can be 
transferred to a computer and read by a GIS, where it is 
transformed into map format. 
APPENDIX 2: GIS Applications 
(http://www.geography.wisc.edu/sco/gis/applications.htm 
1) 
Environment 
Infrastructure and Utilities 
Business Marketing and Sales 
Computer Cartography 
Land Information 
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