notes from last night

[Antti.Roppola at brs.gov.au]

Hi all,

Mapserver can keep raster spatial as a geo-referenced TIFF (GeoTIFF)
or any other GDAL supported format. Vectors can be kept as ESRI Shape
files, in Oracle Spatial, ArcSDE, PostGIS or any OGR supported format.

The map file was originally how you glued them all together as
an entity. But now that you can manipulate a map as an object,
I am only using it to set an initial state. For example, you could
add a layer to a map object that is the result of a complex
query to a PostGIS database:
	"show a 100m radius around wireless nodes within 150m of Barry Drive".

You tell Mapserver what view you would like of the the data in a
map object (which layers, over which extent, in what order etc.)
and it will render a view to the defined output. In most cases, this
will be a PNG to put in a web page. You can also output to PDF,
SVG and other things (I haven't explored this much, just dumping
a higher-res version of the image into a PDF).

Rendering down a 600 x 600 pixel image from a 4000 x 4000 image of
Australia (or 16,000 x 16,000 for LandSat TM!) each time each user
requests a view would be ugly. Fortunately Mapserver does pyramid
layers and tiling so you can usually avoid this. It'll also do spatial
indexing for vector data types, though I'd rather let an RDBMs do
the filtering.

You can do intelligent client side stuff with Mapserver, but the
propritary solutions probably do it better (for now). I really like
being able to support just about every browser and connection. Mapserver
will stream vector data, so find yourself a WMS client rather than
trying to build a GIS using Javascript. :o)

Cheers,

Antti


-----Original Message-----
Anti Roppola
FreeGIS talk


The map is stored as one huge tiff of .au to 250m scale, the system currently
just pulls that information out, combines it with the GIS data and displays it
in a simple png.

Each page on average is about 20KB (that his system sends out)

        See You
            Steve