The HGIS Experience of Drawing Sub-county Unit Boundaries in the Jiangnan Region of Late Imperial China - Space-Time Integration in Geography and GIScience - page 177

Indeed, from the early Ming to the late Qing periods, generations of

local gazetteers from the Songjiang prefecture, or the Songjiang fuji

松江府

([Chongzhen] Songjiang fuji ( ) 1991 ; [Jiaqing] Songjiang fuji

志 崇禎 松江府志

( ) 1991 ; [Kangxi] Songjiang fuji ( ) and [Zhengde]

嘉慶 松江府志 康熙 松江府志

Songjiang fuji ( 1990 ), all recorded information about market

towns in category (18) (i.e., market towns) along with their locations in each bao
unit, their coordinates relative to the county seat and their commerce and industry
specialties. When grouping the towns of each bao together, it is clear that usually
more than one town falls into the area of each division. In total, more than 160 towns
with clear bao identities appear in different versions of the Songjiang prefecture's
local gazetteers. In short, these market town points should be located within the
boundaries of the relevant bao so that if the points of the towns in each division
are plotted on our high resolution base map it would be possible to draft the rough
borders of the bao that encircles those points.
The plotting of the Ming-Qing towns onto the base map began by discovering
the modern residential points of towns with the same or very similar names. We
also tried to compare the modern location of the towns against their locations on
the Ming, Qing and high resolution Republican historical maps of the Shanghai
lishi dituji . If any differences in location were found, we plotted both places, but
tried to follow the earlier-period maps to mark the boundaries of the bao .Inthe
due course of searching for the Ming-Qing town locations, we realized that some of
them no longer exist in modern times, and we could only plot them with reference
to the coordinates given by the local gazetteers and the aforementioned historical
maps. The “Market Town” chapter of the Songjiang fuji , therefore, provides the
coordinates of towns in the form of their relative directions and distances measured
in Chinese li

)

正德 松江府志

, equal to 460 m. After putting those towns on the base map, we then
cross-checked their locations with the coordinate data by using the ArcGIS software
measurement function. It is crucial to point out that our plotted points generally
agreed with the coordination data of the local gazetteers.
The next procedure involved drawing the bao boundary lines around the market
town points. In the GIS field, it is desirable to convert point data to polygons
using the Thessian polygon (also known as the Voronoi polygon) method. These
polygons are created from a point layer by drawing boundaries that separate each
point from its neighbors. The boundaries are located such that they are equidistant
to the two points. Each polygon theoretically contains only one point. This method
makes it possible to recreate boundaries that have never been mapped according
to modern standards, such as the township boundaries of the Songjiang region.
Its limitation, however, is very obvious: the polygons are triangulated into a
triangulated irregular network. In his attempt to recreate the 1971 and 1981 English
and Welsh Enumeration District units, Walford ( 2005 ) found Thessian polygons
unsatisfactory due to their unnatural appearance, and that they were not suitable for
spatial analysis due to their inaccuracy. He used the Thessian polygons only when
no other hybrid approaches were appropriate (Gregory and Ell 2007 : 68-70).

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