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Update "Configuration of Maps" #1162

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111 changes: 17 additions & 94 deletions src/user/configure-the-gis-app.md
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Expand Up @@ -46,38 +46,13 @@ Step 1 - Convert geospatial data to GeoJSON format
Skip this step if your data is already in GeoJSON format using geographic
longitude/latitude.

The recommended tool for geographical format conversions is called
"ogr2ogr". This should be available for most Linux distributions
`sudo apt-get install gdal-bin`. For Windows, go to
<http://fwtools.maptools.org/>and download "FWTools", install it and open
up the FWTools command shell. During the format conversion we also want
to ensure that the output has the correct coordinate projection
(called EPSG:4326 with geographic longitude and latitude). For a more
detailed reference of geographic coordinates, please refer to this
[site](http://www.epsg-registry.org/). If you have already reprojected
the geographic data to the geographic latitude/longitude (EPSG:4326) system,
there is no need to explicitly define the output coordinate system, assuming
that `ogr2ogr` can determine the input spatial reference system. Note that
most GeoJSON files use the EPSG:4326 system. You can determine the
spatial reference system by executing the following command.
Open the files dbf, prj, shp, shx with https://mapshaper.org/

ogrinfo -al -so filename.shp

This command assumes your geospatial data is in ESRI Shapefile (.shp) format,
but [several other formats are supported](https://gdal.org/drivers/vector/).

Assuming that the projection is reported to be EPSG:27700 by `ogrinfo`,
we can transform it to EPSG:4326 by executing the following
command.

ogr2ogr -s_srs EPSG:27700 -t_srs EPSG:4326 -f GeoJSON filename.geojson filename.shp

If the geographic data is already in EPSG:4326, you can simply transform
the shapefile to GeoJSON by executing the following command.

ogr2ogr -f GeoJSON filename.geojson filename.shp

You will find the created GeoJSON file in the same folder as the shapefile.
Click on _Console_ and enter the following command "-prj wgs84", then press
enter. This ensures that the coordinates are in WGS84 format. It could be
the case that the current coordinates are in a format which cannot be processed
by DHIS2, giving you the following error when trying to display a map (the import
will be successful though)

Step 2 - Simplify/generalize your geographical data

Expand All @@ -95,14 +70,12 @@ removing some of the line points. This generalization will
lead to degradation of the polygon. However, after
a bit of experimentation, an optimal level of generalization can be
found, where the accuracy of the polygon is visually acceptable, and the
performance is optimal. Make a backup of your files
before you start. One possible method is the use of
[MapShaper](http://www.mapshaper.org/) which is an online tool which can
be used to generalize geographical data. To use MapShaper, simply upload
your files to the site. Then, click on _Simplify_ in the top menu and
performance is optimal.

In https://mapshaper.org/, click on _Simplify_ in the top menu and
select a simplification method. A slider will show at the top of the screen
that starts at 100%. It is usually acceptable to drag it up to about 30%.
When you are happy with the result, click "Export" in the top right
When you are happy with the result, click _Export_ in the top right
corner. Select the "GeoJSON" file format and click the Export button to
download the file. Move on to the next step with your new simplified
GeoJSON file.
Expand Down Expand Up @@ -166,66 +139,16 @@ has a too small varchar definition. Increase it to 100.
\- Wrongly formatted input GeoJSON, use [GeoJSONLint](https://geojsonlint.com/)
to test the content.

## Importing coordinates in GML format { #gis_creating_setup }

Step 1 - Simplify/generalize your geographical data

The boundaries in geographical data files are usually very accurate, too
much so for the needs of a web-based GIS. This usually does not affect
the performance when using GIS files on a local system, but it is
usually necessary to optimize the geographical data for the web-based
GIS system of DHIS2. All geographical data needs to be downloaded from
the server and rendered in a browser, so if the data is overly complex,
the performance of the DHIS2 Maps will be negatively impacted. This
optimization process can be described as follows:

For polygons, we can make the boundary lines less detailed by
removing some of the line points. This generalization will
lead to degradation of the polygon. However, after
a bit of experimentation, an optimal level of generalization can be
found, where the accuracy of the polygon is visually acceptable, and the
performance is optimal. Make a backup of your shapefiles
before you start. One possible method is the use of
[MapShaper](http://www.mapshaper.org/) which is an online tool which can
be used to generalize geographical data. To use MapShaper, simply upload your files to the site. Then, click on Simplify in the top menu and select a simplification method. A slider will show at the top of the screen that starts at 100%. It is usually acceptable to drag it up to about 30%. When you are happy with the result, click "Export" in the top right corner. Select GeoJSON file format and click the Export button to download the file to your computer.

Step 2 - Convert to GML

The recommended tool for geographical format conversions is called
"ogr2ogr". This should be available for most Linux distributions `sudo apt-get install gdal-bin`. For Windows, go to <http://fwtools.maptools.org/> and download
"FWTools", install it and open up the FWTools command shell. During the
format conversion we also want to ensure that the output has the correct
coordinate projection (called EPSG:4326 with geographic longitude and
latitude). For a more detailed reference of geographic coordinates,
please refer to this [site](http://www.epsg-registry.org/). If you have
already reprojected the geographic data to the geographic
latitude/longitude (EPSG:4326) system, there is no need to explicitly
define the output coordinate system, assuming that `ogr2ogr` can
determine the input spatial reference system. Note that most shapefiles
are using the EPSG:4326 system. You can determine the spatial reference
system by executing the following command.

ogrinfo -al -so filename.json

Assuming that the projection is reported to be EPSG:27700 by `ogrinfo`,
we can transform it to EPSG:4326 by executing the following
command.

ogr2ogr -s_srs EPSG:27700 -t_srs EPSG:4326 -f GML filename.gml filename.json

If the geographic data is already in EPSG:4326, you can simply transform
the shapefile to GML by executing the following command.

ogr2ogr -f GML filename.gml filename.json
Step 4 - Convert to GML format

You will find the created GML file in the same folder as the shapefile.
Go to https://mygeodata.cloud/converter/ and import the GeoJson file.

Step 3 - Prepare the GML file
Select GML as output data and click on “Convert now”.

Unfortunately, the GML file is not ready for importation yet. Open it in
a robust text editor like Geany (Linux) or Notepad++ (Windows). GML is
an XML based format which means that you will recognize the regular XML
tag hierarchy. In the GML file an organisation unit is represented as a
If you haven't added a UID identifier in the GeoJSON file, you can still do it
in the GML file. Open it in a robust text editor like Geany (Linux) or
Notepad++ (Windows). GML is an XML based format which means that you will recognize
the regular XML tag hierarchy. In the GML file an organisation unit is represented as a
\<gml:featureMember\>. Inside the feature members we usually find a lot
of attributes, but we are just going to import their coordinates.

Expand Down