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cover. Land cover mapping is usually performed in the early stages of 
land use planning, where baseline information about natural resources 
and constraints are collected. Map units refer to very broad categories 
of land cover, such as "coniferous forest" or "urban areas". 
Land capability classification identifies those areas with the high-
est potential for a large number of land uses on the basis of their pro-
duction potential. The method is similar to land suitability mapping 
but operates at a more general level. Land suitability mapping is a 
kind of detailed land assessment, i.e. the fitness of land use for a spe-
cific use, e.g. "partly suitable farming with wheat as the best yielding 
crop". 
Normally a soil map serves as a base map to indicate homogenous 
land areas with similar properties (soil type, climate, vegetation). The 
units identified are called land units. It is an area of land which pos-
sesses specific land characteristics and land qualities and which can be 
mapped. 
The starting point for suitability mapping is a mapping of the most 
relevant factors for a given land use. These factors also called land at-
tributes, are divided into 1) land qualities and 2) land characteristics. 
The following "rules of thumb" can be used to identify the land 
qualities which should be part of a land suitability mapping: 
- the land quality must have a substantial effect on performance or 
on cost of production; 
- critical values of the land quality must occur in the planning area; 
- it is realistic to measure or estimate the value of the land quality.
Furthermore, one should beware of variations in values of a given land 
quality during a cropping season and the impact variations have on 
crop yields. Care should be taken to select values from measurements 
representing critical moments in crop growth. 

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