.. _searching:
Searching
=========
The main interface for searching is provided by `OpenSearch
`_ using various extensions including the `Geo and Time
Extensions `_, the
`Extension for Earth Observation
`_ as well as the
`CEOS OpenSearch Best Practice Document
`_.
The OpenSearch URL endpoints are:
* ``/opensearch``: Main service description
* ``/opensearch/``: Search for collections in a specific format
* ``/opensearch/collections/``: Collection specific description
* ``/opensearch/collections//``: Search for products in
a collection in that format
Responses
---------
The description related endpoints provide an OpenSearch Description Document
(OSDD). This XML based file format describes general service metadata and
various access URL templates.
These URL objects provide templates that can be filled with parameters to submit
actual metadata queries. Depending on the used URL, the search result is
returned in one of the following formats:
* ``atom``: Atom syndication format
* ``rss``: RSS
* ``html``: HTML
* ``kml``: Keyhole Markup Language
* ``json``: GeoJSON
The resulting items in that result document can be paged. Specific pages can be
retrieved using the ``offset`` and ``count`` parameters. Additionally, the
response contains links to the first, last, next, and previous pages of the
result set.
The results of the search depend on the type of object being searched. For the
collection search, the result items are collection descriptions of all matched
collections encoded in the selected format. Each description contains a link to
its own specific OSDD document.
In product searches, the result document items are descriptions of products,
containing links to thumbnails, browses, and product specific services such as
WMS or WCS. Additionally it contains the products acquisition footprint and
time stamp.
Filters
-------
The URL templates for both the collection and the record search allow to pass
parameters that control the query and shape of the search. The following table
shows all parameters available for both collection and product searches:
=============== ================================================================
Parameter Description
=============== ================================================================
``startIndex`` The index offset of the items. Used to get subsets of a result
set
``count`` The number of records for each page
``start`` The start time stamp for the time range
``end`` The end time stamp for the time range
``timerel`` The semantic of the time range. Either ``intersects``,
``contains``, ``disjoint``, or ``equals``
``bbox`` The geographic bounding box expressed as ``min-lon``,
``min-lat``, ``max-lon``, ``max-lat`` in WGS84 coordinates
``geom`` A WKT encoded geometry for a geographic search
``lon`` The longitude component of point/radius searches
``lat`` The latitude component of point/radius searches
``r`` The radious in metres of point/radius searches
``georel`` The semantic of the geometry filter. One of ``intersects``,
``contains``, or ``disjoint``
=============== ================================================================
The following parameters are only available in product searches in
addition to the general search parameters:
=============== ================================================================
Parameter Description
=============== ================================================================
``uid`` Filter on identifier
``cloudCover`` Cloud cover filter. Either a specific value or an interval of
values. Values between 0-100
=============== ================================================================
The available parameters depend on the configuration made by the operator.
Samples responses for each of the four URL endpoints are provided in the
:ref:`samples_searching` section of the :ref:`sample_requests` chapter.
Continue reading about the provided :ref:`downloading` services.