[OSGeo-Discuss] Simple Topology File Format Specification
Basques, Bob (CI-StPaul)
bob.basques at ci.stpaul.mn.us
Thu Jun 21 07:40:20 PDT 2012
Before you get too far gone. :c). I would like to encourage you to rethink the idea of using a DB. PostGIS would be great for what you have described, and with some CGI programming, you could pop out SHP file from the database as needed.
We went through all this same type of work some years back specifically for our sewer system. Started out in Oracle, and used AutoCAD topobase for a while, and now run our Web side via a PostGIS sync to the Oracle/Postgis side. Originally, we did the same as you've described, two files (tables) one for nodes, and one for segments. These two tables are enough to capture everything needed to rebuild the structures dynamically for a 3D representation of the sewer system.
From: discuss-bounces at lists.osgeo.org [mailto:discuss-bounces at lists.osgeo.org] On Behalf Of Landon Blake
Sent: Wednesday, June 20, 2012 11:28 PM
To: OSGeo Discussions
Subject: [OSGeo-Discuss] Simple Topology File Format Specification
As part of my recent work for setting up a GIS for a small sanitary sewer district, I've been working on a simple way to share network topology information between GIS systems. The current method for storing and sharing network topology uses two delimited text files.
The first delimited text file stores information about nodes in the network, and relates these nodes to simple features. The second delimited text file stores information about connectors (or edges) between the nodes and relates these connectors to simple features. The two files can be used together to represent network topology. In the future, the method will also store network topology rules.
I'll start work soon on a set of open source plug-ins for OpenJUMP that uses these files to perform network topology analysis and operations on simple features. This includes tasks like simple network route tracing. I would like to split out the low-level code used by the set of network topology plug-ins into a GeoTools module so it can be used by other Java programs.
At this point, some of you are probably asking "why don't you just put all of this in a database?".
There are two reasons:
1) I've got to work with ESRI Shapefiles. I can use OpenJUMP for the project at my day job, but only if my core data files are interoperable with ESRI. (This is horrible, I know, but it is the reality I'm currently dealing with.) I'm not using a geodatabase, and I'm not storing my simple feature data in a database. I need my simple features in Shapefiles and my topology data in stand-alone text files.
2) Databases are hard to share. :]
If there is interest among other OSGeo members, I'd like to write and publish a specification for my topology data files under a Creative Commons License. (I wouldn't claim any intellectual property over the method or file structures either, if that was a concern.) I'd be willing to maintain and update the specification over time.
I looked at CityGML for network topology, but it was way too complex.
I don't want anything resembling XML. :]
Perhaps my use case is too limited to benefit others, but I wanted to shoot something over the bow. I think it would be great to have a way to share network topology between program's like QGIS, UDig, and OpenJUMP.
If there is interest in my work, I'll move this discussion to the OSGeo Standards Mailing List.
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