dhis2-devs team mailing list archive

[Jason Pickering <jason.p.pickering@xxxxxxxxx>]

Also as Knut implies the procedure with the latest release is slightly
different than before. I am not sure it has been changed in the GIS
user manual?

There are also some nice examples here if you are using PostGIS directly

http://www.bostongis.com/postgis_simplify.snippet

As you can seen, this algorithm significantly alters the topology of
the geometry. The Douglas-Peucker algorithm may result in invalid
geometries in some cases, but probably will not matter for thematic
maps anyway.


If you use ArcGIS, the "Integrate"  tool can be useful for
simplification of polygons as well.

Regards,
Jason




On Sun, Nov 7, 2010 at 11:13 PM, Knut Staring <knutst@xxxxxxxxx> wrote:
> On Sun, Nov 7, 2010 at 9:36 PM, Friedman, Roger (CDC/CGH/DGHA) (CTR)
> <rdf4@xxxxxxx> wrote:
>> I have followed the steps for converting an ESRI shapefile to the JSON
>> format as stored in the org unit table.  I am having a difficulty because
>> the boundaries have too many points to fit into the field.  Is there a piece
>> of software out there to replace two segments AB-BC with AC in order of area
>> of ABC or length of AC?  Or do we have to change the field type to
>> accommodate the larger length (and is the performance degradation
>> acceptable)?
>
> There are several ways to achieve simplification (aka generalization)
> of shape files.
>
> I recommend using Mapshaper, which allows you to try out different
> degrees of simplification. Usually up to 80-90% will work nicely.
> http://mapshaper.com/test/demo.html
>
> Once you are happy, download the new .shp and .shx files, and then
> make a copy of the original dbf file and name it the same as the
> simlified shp file. Then use ogr2ogr to convert to GML, do the
> renaming (ogr:Name) and import.
>
> Knut
>
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-- 
Jason P. Pickering
email: jason.p.pickering@xxxxxxxxx
tel:+260968395190