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February 22, 2007

EPSG and WGS and SRIDs, Oh My!

After some pain, sweat, and tears I have learned a lot about projections. For future reference, WGS84 is the projection commonly used for latitude & longitude, which is the same as EPSG:4326. The SRID of which is the same number, whereas the Historic points shape file uses SRID 2253 and NOT 26990 (long story). Fortunately we can use the ArcGIS Toolbox to reproject the data to WGS84 which will save us the headache of identifying each shapefile's SRID. We can now get out shape files to map to the proper projection, and then query across the data points using a bounding box (provided by the map explorer).

It appears that I am going to do some Perl script writting, however, to get all the data into the same place (actually three, but anyway...). As it is, our importer spits out way too much data. To compensate I need to write a Perl script (my kingdom for BASH) to extract the weat from the chaff. Because some of our shapefiles have point data (historic points), others line data (roads), and still others polygons (parcels) we need to store the data in three database tables and query them seperately. I can then take all the results and compile them together. I can make the import data script detect which one it is and select the appropriate table from there.

While you can currently see a version of the map explorer that shows the WKT polygon geometry to query the database against, the live machine has no database to query against. As concequence I set up a Dreamweaver site that uses the XAMPP tool to run a temporary webserver on the Novell machine. This way the php script has access to the database that stores our data for me to run tests against. - The small problem with this is that you need to be logged in as Jen to make it work.

All in all, progress is being made. My next task is working with the temp webserver to see if I can get the php script to effectively query the database.

Posted by shawse at February 22, 2007 12:07 PM


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