.. _coverages:

Coverages
=========

With coverages you can define areas where data is available or where data you are interested in is.
MapProxy supports coverages for :doc:`sources <sources>`, :doc:`caches <caches>` and in the :doc:`mapproxy-seed tool <seed>`. Refer to the corresponding section in the documentation.


There are five different ways to describe a coverage:

- a simple rectangular bounding box,
- a text file with one or more (multi)polygons in WKT format,
- a GeoJSON file with (multi)polygons features,
- (multi)polygons from any data source readable with OGR (e.g. Shapefile, GeoJSON, PostGIS),
- a file with webmercator tile coordinates.

.. versionadded:: 1.10

You can also build intersections, unions and differences between multiple coverages.

Requirements
------------

If you want to use polygons to define a coverage, instead of simple bounding boxes, you will also need Shapely and GEOS. For loading polygons from shapefiles you'll also need GDAL/OGR.

MapProxy requires Shapely 1.2.0 or later and GEOS 3.1.0 or later.

On Debian::

  sudo aptitude install libgeos-dev libgdal-dev
  pip install Shapely


Configuration
-------------

All coverages are configured by defining the source of the coverage and the SRS.
The configuration of the coverage depends on the type. The SRS can allways be configured with the ``srs`` option.

.. versionadded:: 1.5.0
    MapProxy can autodetect the type of the coverage. You can now use ``coverage`` instead of the ``bbox``, ``polygons`` or ``ogr_datasource`` option.
    The old options are still supported.

Coverage Types
--------------

Bounding box
""""""""""""

For simple box coverages.

``bbox`` or ``datasource``:
    A simple BBOX as a list of minx, miny, maxx, maxy, e.g: `[4, -30, 10, -28]` or as a string `4,-30,10,-28`.

Polygon file
""""""""""""

Text files with one WKT polygon or multi-polygon per line.
You can create your own files or use `one of the files we provide for every country <http://mapproxy.org/static/polygons/>`_. Read `the index <http://mapproxy.org/static/polygons/0-fips-codes.txt>`_ to find your country.

``datasource``:
 The path to the polygon file. Should be relative to the proxy configuration or absolute.

GeoJSON
"""""""

.. versionadded:: 1.10
  Previous versions required OGR/GDAL for reading GeoJSON.

You can use GeoJSON files with Polygon and MultiPolygons geometries. FeatureCollections and Features of these geometries are suppored as well. MapProxy uses OGR to read GeoJSON files if you define a ``where`` filter.

``datasource``:
 The path to the GeoJSON file. Should be relative to the proxy configuration or absolute.

OGR datasource
""""""""""""""

Any polygon datasource that is supported by OGR (e.g. Shapefile, GeoJSON, PostGIS).


``datasource``:
  The name of the datasource. Refer to the `OGR format page
  <http://www.gdal.org/ogr/ogr_formats.html>`_ for a list of all supported
  datasources. File paths should be relative to the proxy configuration or absolute.

``where``:
  Restrict which polygons should be loaded from the datasource. Either a simple where
  statement (e.g. ``"CNTRY_NAME='Germany'"``) or a full select statement. Refer to the
  `OGR SQL support documentation <http://www.gdal.org/ogr/ogr_sql.html>`_. If this
  option is unset, the first layer from the datasource will be used.


Expire tiles
""""""""""""

.. versionadded:: 1.10

Text file with webmercator tile coordinates. The tiles should be in ``z/x/y`` format (e.g. ``14/1283/6201``),
with one tile coordinate per line. Only tiles in the webmercator grid are supported (origin is always `nw`).

``expire_tiles``:
  File or directory with expire tile files. Directories are loaded recursive.


Union
"""""

.. versionadded:: 1.10

A union coverage contains the combined coverage of one or more sub-coverages. This can be used to combine multiple coverages a single source. Each sub-coverage can be of any supported type and SRS.

``union``:
  A list of multiple coverages.

Difference
""""""""""

.. versionadded:: 1.10

A difference coverage subtracts the coverage of other sub-coverages from the first coverage. This can be used to exclude parts from a coverage. Each sub-coverage can be of any supported type and SRS.

``difference``:
  A list of multiple coverages.


Intersection
""""""""""""

.. versionadded:: 1.10

An intersection coverage contains only areas that are covered by all sub-coverages. This can be used to limit a larger coverage to a smaller area. Each sub-coverage can be of any supported type and SRS.

``difference``:
  A list of multiple coverages.


Clipping
--------
.. versionadded:: 1.10.0

By default MapProxy tries to get and serve full source image even if a coverage only touches it.
Clipping by coverage can be enabled by setting ``clip: true``. If enabled, all areas outside the coverage will be converted to transparent pixels.

The ``clip`` option is only active for source coverages and not for seeding coverages.


Examples
--------

sources
"""""""

Use the ``coverage`` option to define a coverage for a WMS or tile source.

::

  sources:
    mywms:
      type: wms
      req:
        url: http://example.com/service?
        layers: base
      coverage:
        bbox: [5, 50, 10, 55]
        srs: 'EPSG:4326'


Example of an intersection coverage with clipping::

  sources:
    mywms:
      type: wms
      req:
        url: http://example.com/service?
        layers: base
      coverage:
        clip: true
        intersection:
          - bbox: [5, 50, 10, 55]
            srs: 'EPSG:4326'
          - datasource: coverage.geojson
            srs: 'EPSG:4326'


caches
"""""""

Use the ``coverage`` option to define a coverage for any cache.

::

  caches:
    mycache:
      grids: [GLOBAL_GEODETIC]
      sources: []
      cache:
        type: geopackage
        filename: file.gpkg
        table_name: mygeopackage
        coverage:
          bbox: [5, 50, 10, 55]
          srs: 'EPSG:4326'

.. note::

  You may define a ``coverage`` for both a ``source`` and the ``cache`` defined on that source, in this case the ``intersection`` of both ``coverages`` will be used.
  The ``coverage`` of a ``cache`` is meant to be contained in the ``coverage`` of it's ``source``, in other cases where it either intersects or has no intersection, there may be unexpected bahaviour.

  ::

    Example for defining coverages for source and corresponding cache::
      caches:
        mycache:
          grids: [GLOBAL_GEODETIC]
          sources: [mywms]
          cache:
            type: geopackage
            filename: file.gpkg
            table_name: mygeopackage
            coverage:
              bbox: [-10, -10, 10, 10]
              srs: 'EPSG:4326'
      
      sources:
        mywms:
          type: wms
          req:
            url: http://example.com/service?
            layers: base
          coverage:
            bbox: [-50, -50, 50, 50]
            srs: 'EPSG:4326'

mapproxy-seed
"""""""""""""

To define a seed-area in the ``seed.yaml``, add the coverage directly to the view.

::

  coverages:
    germany:
      datasource: 'shps/world_boundaries_m.shp'
      where: CNTRY_NAME = 'Germany'
      srs: 'EPSG:900913'

.. index:: PostGIS, PostgreSQL

Here is the same example with a PostGIS source::

  coverages:
    germany:
      datasource: "PG: dbname='db' host='host' user='user'
    password='password'"
      where: "select * from coverages where country='germany'"
      srs: 'EPSG:900913'


.. index:: GeoJSON

And here is an example with a GeoJSON source::

  coverages:
    germany:
      datasource: 'boundary.geojson'
      srs: 'EPSG:4326'

See `the OGR driver list <http://www.gdal.org/ogr/ogr_formats.html>`_ for all supported formats.
