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Locating socio-economic activities with GIS in Chines cities
Based on their spatial characteristics, existing referencing methods can be categorized into three types
of location referencing schemes: the name-based scheme, the street-based scheme, and the coordinatebased
scheme. The first two schemes mainly deal with locating socio-economic activities by semantic
expression, and will be examined in detail. Examples of the first two schemes are:
- Name-based (point/polygon): building, place name, large or popular site, street intersection, street,
administrative unit, telecom zone, postcode zone
- Street-based (line): street address, mile-post
The name-based scheme provides direct linkage between activities and base maps, using semantic
names as keywords. The referencing base is a set of geographical entities with which names are
associated. A scoring system can be set up to cope with mismatched cases. In the absence of correct
matching, a remedial process can be started to search possible candidates and to call for human
interacting. The street-based scheme is basically a linear matching method in which the relative
distance from a known origin is needed to determine a location. The scheme is applied on road
networks to locate traffic events and road condition on roads. The main feature of this scheme is that
the process includes linear interpolation to identify a location along a road.
Referencing bases
The conditions of the location referencing bases under the two schemes vary from country to country.
Some of the practiced or possible methods in China are briefly discussed here.
Street name and street intersection Since the street network forms the spatial structure of a city, streets
can be effective in location referencing. The problem with street location lies in its geographical
precision. A shorter street indicates a more precise spatial location than a longer street. When street
addresses are not available, street names could be used as a substitute. In many cases street
intersections are used as referencing points, e.g. in traffic navigation and incident management. The
potential problem with street name and street intersection matching lies in its incomplete or wrong
expression of street names.
Street address. The street address has been the most popular and important means of locating
socioeconomic activities in space in well-developed cities. Street addresses provide geographical
locations. The system has been created and maintained by the sector of public security in China, and
has been widely used in post for address expression. However, the expression of address is not directly
suitable to a standard address matching process. The major difference is that it is very difficult to
extract the road name and the address from a conventional address expression. It is apparent that a
translating program is necessary if the Chinese address is to be applied in the standard address
matching process. Another problem is that the Chinese street numbers are sometimes not assigned in a
systematic way. This is partly due to the indifference or inefficiency of the offices, and partly due to
the fast-growing renovation or reconstruction during economic booming.
Postcode. Postcodes are tightly associated with mail delivery. The formulation of postcode is a
systematic scheme that takes a hierarchical allocation. The accuracy of postcode is reflected in the
spatial units represented by the lowest level of postcodes. Postcodes can also be represented in detail
by point, as is the case of the ZIP+4 address point in the US postal database (Cowen, 1997). The
postcode in China is a national 7-digit system. If used for location reference in a city for such study as
transport modeling, the postcode zones are too big in terms of geographical area. For example, the
built-up area of Wuhan is about 230 Km2, yet it is divided into only 25 postcode zones. Furthermore,
the shapes and sizes of postcode areas are very different from one zone to another.
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