[Geotools-gt2-users] Lots of Features, Small Resolution

[Trevor S. <ts...@ty...>]

Greetings everyone,

Our use of Geotools is in a client-server situation.  We use the
StyledMapPane on the client, which makes requests to a small wrapper
around calls to DataStores.  The client knows its area of interest, and
includes that in the request; the server sends back serialized feature
wrappers (I posted the code to do so on the Wiki some time ago).  There
are two main situations in which we display a StyledMapPane.  When a
user starts our application they see an "overview map" of the whole
county, showing a few layers which make sense at that size, such as
rivers and major roads.  When they zoom in to a certain depth other
layers, such as parcels, will load.  For the other use case, they call
up a specific parcel and see that parcel and a few neighboring ones and
then can maneuver in the map if they desire.

Our architect did some profiling recently and noticed that the memory
usage from loading the overview map was on the order of 20MB (the rest
of the app takes about 6MB on startup), and created well over 100,000
Coordinate objects.  I'm not surprised at this number of coordinates,
since rivers and roads tend to have a lot of points.  However, since the
map is only about 200 pixels square, many of these points are sent
unnecessarily, because they won't get rendered as separate points.  Our
architect asserted that we should be able to filter features that would
be smaller than a pixel (easy) and transform the remaining geometries to
match the desired resolution.  A line with lots of small wiggles when
viewed at high resolution looks straight when viewed from low
resolution, so there's no reason to send all the extra data until the
user zooms in, at which point it would be sampled at a higher
resolution.

What's the best way to do this?  Is there already a Geotools or JTS
method I can call to perform this operation?  If there isn't, and I were
to write it, where in Geotools would it belong?  (I'm assuming this
would be a generally useful method...)  Is there a better way of
accomplishing the same goal (i.e. optimizing geometries for memory
size)?

Thanks,

-- 
Trevor Stone | Software Engineer | tel 800-554-4434 ext 208 | fax 303-271-1930 | email ts...@ty...
Tyler Technologies | Eagle Division | 14142 Denver West Pkwy Suite 155 | Lakewood, CO 80401 | www.tyler-eagle.com