International Workshop on Historical GIS

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Web Implementation of CHGIS and Spatio-Temporal Searching

Merrick Lex Berman
CHGIS, Harvard Yenching Inst, USA

In addition to the technical difficulties to be dealt with when developing GIS datasets we are also faced with the challenge of creating user-friendly means of access to the data over the Internet. The trend toward providing webmap servers loaded up with some of the data layers is one attempt to address this, however redesigning the webmap interface to enable the various types of searches and analysis we wish to perform often results in overly complex and non-intuitive interfaces. As part of the CHGIS project, we have been working on a two stage model to streamline the search process.

The first stage makes use of relational tables in a MySQL database to sort out the placenames and historical instances of those names. Explicit positions in the administrative hierarchy, as well as dates, are employed to disambiguate places with the same name. The user can then continue searching the database for parent or child relationships, or database records with certain topological values such as adjacency, and overlap, (which have been calculated and stored in advance in the database).

The second stage is to launch a webmap server containing GIS layers of spatial data that correspond to the objects in the database. These can be variously displayed as a group of points, lines or polygons, or as a simple extent (determined by a bounding box).

By conducting preliminary searching and basic spatial analysis in RDBMS, we can eliminate those features from the webmap interface and simplify our webmaps to include only the most rudimentary zoom, pan, and query functions. The search process is handled easily and efficiently in the database, while the webmap server is only employed to display the results.

A preliminary version of the web implementation (for 1990 Chinese Counties) is posted at:

http://chgis.fas.harvard.edu/tools/gb91.html

International Workshop on Historical GIS Fudan University, Shanghai, August 23-25, 2001