Administrative units and spatial aggregation schemes

The spatial aggregation schemes used in the coverages differ in their treatment of the urban wards and surrounding counties. In terms of the PRC administrative heirarchy, urban wards (qu) are of the same status as other county-level units. However, the small size of wards makes it impractical to map them at a common scale with the counties, moreover, for many analytical purposes, it is useful to aggregate urban wards. The following provides a description of four generic spatial aggregation schemes referred to in CITAS documentation by their initials:

FD: Fully Differentiated coverages include separate records for every urban qu as well as every county-level unit. Each urban qu has been assigned an official GB Code and these will be used in such a map.

MQ: Merged Qu coverages bring together selected urban qu, mainly central city wards. The MQ scheme distinguishes between central city districts (which are merged) and traditional peri-urban counties which have been designated as urban qu in recent times. For example in a 1990 MQ coverage, Liaoning's Anshan shi will consist of two polygons, one coded 210311 for Anshan: Jiupu qu and another assigned the code of 210351, called Anshan shi CC, consisting of the urban qu's 210302, 210303 and 210304. A list of aggregated units, along with information on the assigned codes and their urban qu components, will be available for any base map that uses this scheme.

SXQ: Shixiaqu coverages bring together all urban qu's that are administered by the city (i.e., belonging to its shixiaqu). This is an officially recognized aggregation scheme, and polygons of the SXQ are assigned the official SXQ GB Code.

MC: A Municipality-Compatible coverage merges together certain tightly drawn municipalities with their surrounding counties. This is done to compensate for arbitrary differences in the administrative geography of municipalities in relation to other county-level units. For example in a 1986 MC coverage, Liaoning's Chaoyang shixiaqu (211301) and Chaoyang xian (211321) will be merged together to form one MC unit, Chaoyang MC, and both assigned the code of 211461. A list of such units, including information on the assigned codes and their city and county components, will be available for any base map that uses this scheme.