[gdal-dev] Shapefiles2tiles

Jorge Arévalo jorge.arevalo at deimos-space.com
Tue Nov 2 14:53:27 EDT 2010

Hi everybody, I'd like to ask you how to improve a process

Context: Show vectorial data in Google Maps, applying given colors to the data

Input data: A bunch of shapefiles, MIF format.
Output result: tiles to overlay on google maps
Process: One field of the shapefiles tells us the color of each
polygon. We create empty GeoTiff files, burn the MIF files into them,
applying the needed colors, and execute gdal2tiles over the GeoTiff
files, creating small PNG tiles to overlay on Google Maps (zoom levels
4 - 14)

Problem: The MIF files are about 200 - 250 MB average. Resulting
GeoTiff files are about 7 - 8 GB (size about 30000 - 50000 pixels).
The process is really slow. More than 24h to generate GeoTiff files,
burn vectors into them and generate the tiles.

Summarizing: MIF files (~200-250MB) ---> GeoTiff files (~ 7 - 8 GB)
---> Google Maps tiles

First step performed by gdal_rasterize and some additional python code
(to create empty raster). Second step with gdal2tiles, "near"
resampling method

Question: is there a faster way to overlay vector data on Google Maps,
applying colors? Without installing Geoserver, Mapserver. Only a web
server (apache). Or at least, improve the entire process of
rasterizing - creating tiles. If there's a problem during gdal2tiles
execution, you need to start again creating all the tiles.

BTW, the result here:

Many thanks in advance, and best regards
Jorge Arévalo
Internet & Mobilty Division, DEIMOS
jorge.arevalo at deimos-space.com

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