dhis2-devs team mailing list archive

[Knut Staring <knutst@xxxxxxxxx>]

An additional thought - with JTS or Geotools, it should be possible to
eliminate the ogr2ogr conversion to GML and rather parse the
(simplified) shapefile directly. However, this is probably not urgent.
Here is a quick presentation of the two libraries:
http://haitaoblog.blogspot.com/2008/01/jts-topology-suite-geotools.html

On Thu, Nov 11, 2010 at 7:32 PM, Knut Staring <knutst@xxxxxxxxx> wrote:
> On Thu, Nov 11, 2010 at 6:05 PM, Jan Henrik Øverland
> <janhenrik.overland@xxxxxxxxx> wrote:
>> Hi,
>> I would like to suggest that we finally remove the map source types
>> "GeoJSON" and "Shapefiles" from the GIS client. They are not able to offer
>> most of the functionality that will be implemented in the future and even
>> maintaining them as they are would hamper the development of new
>> functionality considerably. However, overlays could still be loaded from
>> local geojson files.
>> In other words, I would like to control the geojson input to the thematic
>> widgets completely by letting our own server produce it.
>
> I think this is mostly ok, but I also think it requires us to improve
> the importing and limit it to one polygon layer and one point layer -
> see below
>
>> This geojson may contain data from Geoserver, health surveys etc.
>
> Not quite I understand - you mean we can import data from such
> sources? As far as I know, that is not the case now - we can only
> import from GML.
>
> Recent discussion on the list has revived the need for more support
> for data loading.  I think the hierarchy is a good place to start
> improving. I have come to realize that it is actually a bit stupid to
> import polygons at different levels (nation, province, district,
> subdivision etc), because the higher levels should logically
> correspond to fusion of lower level polygons. Therefore, I suggest the
> following algorithm for starting in a new country:
>
> 1) Start with the lowest level for which you have polygons (e.g.
> shapefiles), and simplify it to an acceptable degree (using e.g.
> Mapshaper)
>
> 2) Create the organizational hierarchy in a standardized .xlsx
> template with a worksheet that has columns like this:
>
> Country, Province, District, Subdistrict, Facility (the number of
> levels and their names will vary - this should probably be specified
> in a front worksheet.
>
> Make sure the names of the level in step 1) correspond exactly to the
> shapefile names.
>
> Also, there will be two columns at the end, immediately after
> facilities, which can be filled with point coordinates if available.
>
> 3) Upload the Excel file to DHIS2, which will run it through an XSL
> transformation that builds the whole hierarchy
>
> 4) Upload the simplified polygon layer. DHIS2 will not only poplulate
> the orgunits for that level as it does currently, but also
> automatically *all levels above".
>
> For step 4, we probably need to use GIS Java capabilities like JTS or
> Geotools (maybe even steal some code from Geoserver, uDig or OpenJump)
> http://lin-ear-th-inking.blogspot.com/2007/11/fast-polygon-merging-in-jts-using.html.
> With such tools in place, we could probably also do the simplification
> in step 1, but it is actually quite good for people to have the
> manually guided visualization that Mapshaper offers instead of
> automated generalization.
>
> Knut
>



-- 
Cheers,
Knut Staring