Re: shape files

Hi Chris,

On Monday, May 6, 2002, at 02:47 PM, Chris Mamorella wrote:

> Don,
>
> Are there any shape files available that I can download to substitute
> in place of the current map shape files? I ask this because the
> political boundaries on OpenMap's shape files are not very accurate in
> certain spots.

The dcwpo-browse.shp files were created from browse-level DCW data, so
there are definitely inconsistencies at large scales. You can use the
vmap_area_thin.shp and vmap_edge_thin.shp files (in separate layers) for
more accurate data, but these files have also been thinned from VMAP
level 0 data, and also get more inaccurate at larger scales. You can
download full resolution vmap_edge and vmap_area data, created from VMAP
level 0 political boundary data, from
http://openmap.bbn.com/data/vmap_political_world.tar.gz

If you need more detail, you can download VMAP data from
http://geoengine.nima.mil, and use the
com.bbn.openmap.layer.vpf.VPFLayer to display it. There may be
performance implications for this, as VPF data can be pretty large.

Another solution may be the ScaleFilterLayer, which toggles between
layers depending on the projection scale. You can use the thinned data
at small scales, and switch to better resolution as you zoom in.

> Also, what software do we need to create and view shape files?

To view shape files in OpenMap, you have two options - the
com.bbn.openmap.layer.shape package, which has the ShapeLayer, and the
com.bbn.openmap.plugin.esri package, which has the ESRIPlugIn.

The ShapeLayer doesn't use the dbf file for anything, but creates a
spatial index file so that it only gathers the shape file graphics that
are currently on the map. It's better for larger shape files that serve
as background layers.

The ESRI package has classes to read and write shp, shx and dbf files,
and the plugin palette will display the dbf contents. It also provides
interaction with the dbf and the map graphics. It loads the whole shape
file, though, so larger shape files can use up a lot of memory.

Hope this helps,

Don

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Don Dietrick, BBN Technologies, dietrick@bbn.com
10 Moulton Street, Cambridge, MA 02138
617-873-3031 [fax]-2794
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