gis

We had this big raster that we needed to chop up into tiles and only extract a portion of for load into PostGIS. raster2pgsql doesn't currently have an option to pull just a portion of a raster and also we don't have the windows raster2pgsql compiled with MrSID support. Luckily GDAL commandline gdal_translate has this switch that allows you to specify a chunk of a raster to grab based on a projected or unprojected box window. We wanted to grab just that portion that is part of boston and chunk it into bite size pieces. What we needed was a grid generator similar to what we described a while back in Map Dicing and other stuff that would chop our neighborhood into bite sized tiles we could then use to generate the relevant gdal_translate command. Instead of using temp tables and all that stuff, we decided to try with the ST_Tile raster function. Creating an empty raster and then tiling it.

In a nutshell, we're using PostGIS raster technology (ST_Tile function introduced in PostGIS 2.1) that we demonstrated in Waiting for PostGIS 2.1 ST_Tile to create a grid because PostGIS geometry doesn't have cool gridding function like SpatiaLite has :). SpatialLite tesselation. Perhaps in PostGIS 2.2 we'll see some of these SpatiaLite niceties. However ST_Tile does the trick fairly nicely and quickly. For this example took under 600 ms to generate 1524 rows of GDAL commands.

Following PostgreSQL's lead, I thought it would be nice to provide PostGIS manual in ePub format. It turned out not to be a lot of work, but probably a lot more to fine tune it. I've changed Debbie (a PostGIS build-bot) to build this format and publish to PostGIS site whenever a change to PostGIS 2.1. You can download from http://postgis.net/documentation. The link next to EPUB.

I would appreciate if people could try it out on their eReader devices. On my Android tablet it looks pretty good, and had the nice feature of when I clicked on the epub link to download it, it added it to my library. I can't figure out how to click on the links (probably because I just use my desktop). and table of contents seems to crash the reader. On my windows firefox ePub viewer, it looks pretty yucky but much easier to navigate. I guess there are a LOT of differences with ePub readers.

As mentioned in prior article we have windows binaries available for upcoming pgRouting. When we get new things, we like to take them for a test drive. So we've put up our first tutorial ever on pgRouting: pgRouting: Loading OpenStreetMap with Osm2Po and route querying. The OSM2PO pgRouting loading content we borrowed from Anita Graser's An osm2po Quickstart, but put a Boston spin to it.

We hope to use this tutorial series as a springboard for testing the radical changes in pgRouting currently going on.