For each WMS GetMap? request, Mapserver appears to fully resolve all projection
definitions in the .map file, even for layers that aren't involved in the GetMap?
request.
This isn't a huge problem when projections are fully defined within each .map
file layer. But when using "init=EPSG" syntax, Mapserver will go to the Proj
"epsg" file once for each layer.
The issue is speed. My experiments have shown that this slows down GetMap?
responses by a few hundred milliseconds to a few seconds (depending on the
number of layers and the placement of the projection definition within the
"epsg" file.
Possible solutions:
a) only resolve EPSG codes for layers that are involved in the current map request
b) cache the projection definitions, so we don't need to go to the "epsg" file
for every layer
