2004 
  
CONSTRAINT-BASED GENERALIZATION OF SOIL MAP’ 
GAO Wenxiu, SONG Aihong, GONG Jianya 
National Laboratory of Surveying, Mapping and Remote Sensing, Wuhan University 
129, Luoyu RD. Wuhan, China, 400079 
Email: wxgao@mail.liesmars.wtusm.edu.cn 
Commission VI, WG VI/4 
KEYWORDS: Constraint-based Generalization, Specific constraints, Generic constraints, Soil map generalization, Integration of 
constraints 
ABSTRACT: 
Soil map that shows the geographical distribution regularity of different soil types and the soil resources diversity is an important 
type of categorical maps. And soil map is applied in various professional studies such as vegetation studies, land use and 
environmental studies, and resources management. Therefore, soil map generalization not only follows the generic principles of 
cartographic generalization, but also is supervised by the professional principles of soil distribution. This paper explores the 
professional principles of soil distribution according to the regularity of soil distribution, the characteristics, representation and 
application of soil maps as specific constraints to soil map generalization. The specific constraints are indispensable for the 
comprehensive generalization of soil map. Then associating with the research of Peter and Weibel (1999) on generic constraints to 
generalization of categorical data, the specific constrains and generic constraints are integrated and applied in the different phrases 
of the generalization process to investigate the functionalities. The last component of this paper discusses two special issues of soil 
map generalization to demonstrate the importance and application of specific constraints to soil map generalization. 
1. INTRODUCTION distribution regularity in larger geographic regions from the 
macro view of point (Lu ef al. 2001). One of the functions of 
Soil data is one of the important components to portray the soil map generalization is to derive smaller-scale map from 
natural environment and natural resource in agriculture, Soil larger-scale map. 
map, which includes map of soil parent materials, soil category 
map, map of soil chemical types, map of soil texture and so on, Furthermore, the purpose and application of soil map decide the 
is one of the important types of land resource map and level of detail representation of soil categories in the map, and 
agriculture map. Soil category map represents soil categories, they also decide the representation and completeness of a 
soil geographic distribution regularity and diversified soil feature. For example, the categories of a soil map (called Map 
resources in natural environment. In many literatures, soil A), which is used to discern the adaptability of soil for the 
category map is just called soil map (Pan ef al. 2002; Lu ef al. — plantation of vegetations or the reasonable layout of crop 
2001; Huang et al 1989). In the paper, we use soil map instead ^ plantation, must be more complete than that of a soil map 
of soil category map to discuss the constraints of soil map (called Map B) which is 4as a reference map to partition the 
generalization. agricultural districts (Huang ef a/. 1989, Liao 1991). Map B 
According to the purpose and application of soil map, soil map could be derived from Map A, which could just generalize the 
consists of generic soil map and specific soil map. The former ^ content of the map without any change of the map scale. This is 
one represents the generic characteristics of soil, while the latter the another important function of soil map generalization. 
one focuses on one or more specific characteristics of soil, such 
as the map of soil engineering, the map of forest soil, the map [In brief, soil map generalization could be employed in the two 
of soil erodibility (Huang et al. 1989). Chinese Soil Taxonomy situations: one is to derive middle-scale or small-scale soil maps 
(CST) (revised proposal, 1995) is employed as the base of soil ^ from large-scale soil maps; the other one is to derive soil maps 
mapping, which is a multiple category classification including with generalized contents from soil maps with complete 
six categories, namely soil order, soil suborder, soil group, soil ^ contents. The derived maps in the first situation represent the 
subgroup, soil genus and soil series according to the order from soil distribution regularity in a larger geographic region than 
higher category to lower one. Soil maps at different scale that of the original maps, whereas the derived maps in the 
represent different level of soil category. The soil maps.with the second situation represent the coarser characteristics of soil 
scale 10150000 or more than 1:50000 called large-scale soil distribution in a same geographic region as that of the original 
map describe the soil categories in soil genus level, which ^ maps. Whatever kind of situations, soil map generalization 
represent the detailed soil distribution in small-domain terrain should be implemented based on generalization constraints to 
environments (Lu er al. 2001). The middle-scale soil map, steer generalization operations and derive valid products. 
1:50000~1:500000, and the small-scale soil map, smaller than 
1:500000, could describe the soil categories in the soil group or Our study focuses on the constraints involved in soil map 
soil subgroup (Huang er al. 1989), which represent the soil ^ generalization, especially specific constraints based on the 
  
: Study supported by the Open Research Foundation of the Key Laboratory for Information Engineer in Surveying, Mapping and 
Remote Sensing (LIESMARS) (No. (02)0401) and 973 Program (No. 2003CB415205) 
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