Using SVG for online digitizing and editing of geographic data

Abstract for the SVG Open conference, Tokyo, 2004

Andreas Neumann
Institute of Cartography, ETH Zurich
ETH Hoenggerberg, CH-8093 Zurich

Fax: ++41-1-6331153
neumann@karto.baug.ethz.ch

keywords:

digitizing, OpenGIS geometry, spatial databases, PostgreSQL, PostGIS

The presentation will show a prototype for online digitizing of geographic data. A map application was created to efficiently navigate in larger geographic datasets. Various map layers can be displayed as reference layers. Specific layers can be edited. The application allows for digitizing and editing of point, line and area features. The supported feature types correspond to the OpenGIS features "POINT", "MULTIPOINT", "LINESTRING", "MULTILINESTRING", "POLYGON", "MULTIPOLYGON" and can be grouped in "GEOMETRYCOLLECTION"s. Data can be loaded from and to spatial databases. In our first prototype we used Postgis (the spatial extension to PostgreSQL) for that purpose. However, the database backend should be adoptable to other spatial databases as well.

The following operations are supported by the digitizing environment:

Regarding the coordinate system, we use already projected or unprojected "real world coordinates" in map units (f.e. meters or lat/long), with an inverted y-axis. While digitizing and editing data, we store the data in nested ECMAScript arrays. Before sending geometry to the spatial database, we convert it to the OpenGIS feature types.

Applications

The application is currently in use by the Alexandria Digital Library (UC Santa Barbara, California) as part of an image cataloging tool for geomorphologic images. Experts in the geology domain can attach images to point, area and line features. The prototype makes also use of the OGC WMS services available by USGS and Microsoft Terraserver, f.e. for the purpose of loading digital orthoimages or scanned raster maps (DRGs). A screenshot of the project is shown below:

Screensho Image Cataloging Tool

Currently, we work on a second project leveraging the same digitizing technology. The swiss federal railways wants to offer forest engineers online access for aquiring and editing forest data (point features for single trees and area features for contiguous forest areas) along the swiss federal railway tracks. Map data is served by an Intergraph Geomedia webmap server. New and edited features are transfered using the OpenGIS Simple Features for SQL format. This project is carried out in colloboration with Basler & Hofmann, a planning and geoinformation consulting company in Zurich. This work is currently in progress but should be almost finished by the time of the conference.