dhis2-devs team mailing list archive

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

Without going into the inner guts of GML, which can be terribly
complex, let me first elaborate a bit on the use case. In an certain
country I have recently been in, a seperate GIS system will be setup
for supporting the master MoH plan. They will need to calculate for
instance, accessibility of health facilities to the population. While
it may be possible for a given external GIS client (Qgis, ArcGIS,
DivaGiS, etc, etc) to consume GeoJSON, the question then becomes is
the the "right" thing to do. We would prefer not to have two
repositories, of for instance health facilities, and then have to
worry about how to sync them.

I have understood from the beginning of the DHIS2 GIS client, that it
was based on simplicity and speed. I think it has been a great
success, and achieved much more than I really thought possible in such
a short time. I do not think we should complicate things too much and
lose sight of the original intentions of the DHIS2 GIS client.

However, I would like to see that DHIS2 can either 1) serve as a
repository of GIS data, in which case it needs to be able to support
things like GML or projection definitions to serve to external clients
that may need this OR 2) consume data in standard formats from another
repository. Both would be great of course, but we do not want to
rewrite Geoserver. I think there is a blueprint out there that would
allow (when implemented) DHIS to consume data from a WFS, and then
transform this data into its own internal representation (In this
case, GeoJSON).  It is also theoretically possible to use the
Geoserver, with an attribute or view, to present to Geoserver, which
could handle the heavy WFS/WMS lifting if required.

I guess I am sort of favoring implementing some sort of GML support,
as this would pretty much easily allow other clients to take a DXF
file and transform it into something that they could use directly. If
the internal representation of the data is needed in GeoJSON for
performance and simplicity reasons, I think this might be OK for now.
However, I think what is represented in the DXF (or SDMX-HD) file,
which may be used by either DHIS2 systems or other systems, then
representing the point/polygon in GML would be a more standards based
approach. One possible way would be to store the data in native GML
format, and then transform it into GeoJSON (sort of like a data mart)
for presentation to the mapping client.

 Just some ideas...

Regards,
Jason


2010/5/19 Bob Jolliffe <bobjolliffe@xxxxxxxxx>:
> Just took a very quick look at the schema for gmlSimpleFeaturesProfile
> (attached).
>
> It is a limited subset of gml which allows (amongst others) the
> following simple constructs
>
> <!--<Polygon xmlns="http://www.opengis.net/gml";
>    <interior>
>        <LinearRing>
>            <posList>
>                10 10
>                20 20
>                25 32
>                12 45
>                22 45
>            </posList>
>        </LinearRing>
>    </interior>
>    </Polygon>-->
>
> <!--<Point xmlns="http://www.opengis.net/gml";>
>    <pos>10 10</pos>
> </Point>-->
>
> We'll see what Knut provides back and see whether these are
> sufficient, but these do seem to to map against what we have.  There
> are of course additional optional attributes and elements but if we
> don't model them we don't need to produce them.  Not sure if I go for
> all the inner ring stuff but then again what I know about GIS I could
> write on the back of a cigarette box.  Others will know better.
>
> Regards
> Bob
>
> 2010/5/19 Lars Helge Øverland <larshelge@xxxxxxxxx>:
>>
>> Thanks for valuable input. Using GML in one way or the other was part of the
>> plan as it seems the most versatile format among those produced by
>> Geoserver.
>> Before deciding I really need to see some more examples of Shapefiles. The
>> ones for SL are a bit weird as Geoserver produces invalid XML when exporting
>> the facility layer to GML (one reason is that the name column is called
>> "name of fa" and that is attempted translated into an xml element).
>> Does anyone have a couple of "standard" shapefiles? I guess the WHO ones are
>> the closet we get to that. Knut, could you provide some more examples of
>> that (without me having to sign and fax a bunch of forms like last time:-) ?
>> Lars
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-- 
--
Jason P. Pickering
email: jason.p.pickering@xxxxxxxxx
tel:+260968395190