Hello,

I've come across some behavior from GeoServer that I would consider a bug,
but wanted to post it to this list for feedback before posting to JIRA.

I have been using GeoServer's WMS to produce maps in EPSG:2163 based on
Natural Earth country and province boundaries that are stored in PostGIS in
EPSG:4326.

I noticed that GeoServer is simplifying the geometries when it fetches them
from the database, using ST_Simplify. Simplifying with any tolerance causes
removal of vertices along parallels and meridians. Removal of these
vertices before reprojection causes severe misalignment between country and
province layers in the resulting map. An example (US-Canada border) is
shown below:

[image: image.png]

To avoid this, it seems like GeoServer should either:

a) use PostGIS to perform the transformation, before doing on-the-fly
simplification ( SELECT ST_Simplify(ST_Transform(geom, 4326, 2163),
0.123456) )
b) or, avoid doing on-the-fly simplification when data is being fetched
from a CRS with a data store

I am able to work around the problem by disabling on-the-fly simplification
for the data store, but this is not desirable because most requests do not
involve a transformation and thus benefit from simplification.

Dan
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