|Figure 1: Parks table, first ten records ordered by "gid" column.|
|Figure 2: Parcels table, first ten records ordered by "gid" column.|
The second module of Advanced Topics in GIS built upon the introduction to entity relationship diagrams (ERDs) last week to include a physical model, the next step after the logical model. The ERD of the physical model is similar to the logical model, but it includes the datatypes of each attribute. This gets us closer to a database model that can be directly implemented as tables in a database.
The bulk of the time spent on this module's exercises, however, focused on using PostgreSQL and PostGIS to create, import and query spatial and non-spatial data. This was a good introduction for me, and a welcome addition to skills learned previously from ArcGIS and Oracle products. The figures above show sample data from two tables populated by data imported from shapefiles using the PostGIS Shapefile Import/Export Manager utility. After connecting to the desired PostgreSQL database, the user must input the SRID number defining the spatial coordinate system of the data. The method used for this module was to utilize the online conversion tool located at http://www.prj2epsg.org. Once the SRID number is defined in the PostGIS utility, the shapefile is imported as a PostgreSQL table.
This module was just the beginning of the integration of GIS and database skills covered in previous courses in the UWF program. I look forward to seeing how far we can go this semester.