[postgis-users] using simplify and snaptogrid for a global coastline plot

[chris hinkle]

Hi gang,

Some background info before I present my questions:

I've been teaching my self PostGIS and GIS in general for that last few
weeks.

My main source of "bootstrapping" education material has been the O'Reilly
book, Web Mapping Illustrated, which introduced me to PostGIS and OGR.

My workflow is this:

1.) Find data on the web
2.) Get it into a shapefile somehow
3.) ogr2ogr the shapefiles into PostGIS
4.) ogr2ogr the postgis data into GML files using sql to refine the data and
edit the geometry for the specific need.

Currently I'm trying to create a single data file which plots out the
coastlines for the entire globe, at a low detail level suitable for quick
plotting and animation (think google earth zoomed out all the way)

My data source is the VMAP0 dataset which used to be the Digital Chart of
the World.

Right now I'm using this sql to create my GML:

SELECT ST_SnapToGrid( ST_Simplify(wkb_geometry, 5), .5, .5 )
FROM europe_north_asia_coastlines
UNION ALL
SELECT ST_SnapToGrid( ST_Simplify(wkb_geometry, 5), .5, .5 )
FROM north_america_coastlines
UNION ALL
SELECT ST_SnapToGrid( ST_Simplify(wkb_geometry, 5), .5, .5 )
FROM south_asia_austrailia_coastlines
UNION ALL
SELECT ST_SnapToGrid( ST_Simplify(wkb_geometry, 5), .5, .5 )
FROM south_america_africa_coastlines

Questions:
1.) What do people think of my workflow
2.) What do people think of my data source choice
3.) Am I doing the geometry editing right?  It seems I'm missing a step,
because I'm simplifying the data, but I'm still working with a bunch of
features, don't I want to combine my features somehow?
4.) Am I on the right track?
5.) Is this the best list for these questions?

Thanks,
Chris



-- 
Chris Hinkle
Brooklyn, NY
lilhinx at gmail.com
646-240-3024
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