WHAT YOU TYPE IS WHAT YOU SEE: COMPARING TWO WEB-BASED OPEN SOURCE APPROACHES TO DISPLAY THE RESULTS OF SPATIAL SQL QUERIES
Can you tell what the result of the spatial query 'SELECT ST_Intersection( ST_Buffer( ST_GeometryFromText( 'POINT(40 30)', 4326), 10), ST_Buffer( ST_GeometryFromText( 'POINT(30 40)', 4326), 10 ) )' looks like? Neither can we – but in times of the post web-2.0-era there should be some online tool to test and visualize your PostGIS-query, shouldn't it?
There are at least two recent attempts at solving the outlined problem of visualizing results of spatial SQL: WYTIWYS (a small byproduct of a publication about the OSS-WebGIS-stack by M. Jansen and T. Adams, http://openlayers-buch.de) and postgisonline.org, a webpage by N. Avén (http://postgisonline.org). In the talk we will present the ideas behind the software and the different approaches taken.
We believe that an instant feedback to SQL-queries is very helpful in order to understand and fully embrace the power behind PostGIS. And which feedback to spatial queries is the best – we think it is a visual one. When teaching PostgreSQL/PostGIS the concepts behind (and effects of) operations like merging, dissecting, buffering etc. are far easier to understand, when the result of running a SQL command is a map, something people can easily wrap their minds around.
Both presented projects are young and in an early development stage so that there is plenty of room for the integration of possible feedback and feature wishes of the audience.
Marc Jansen - terrestris GmbH & Co. KG
Nicklas Avén - postgisonline.org