Module for Omeka S that adds data types "geometry" and "geography" to store markers and area highlights on images and maps with wkt
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README.md

Data type Geometry (module for Omeka S)

Data type Geometry is a module for Omeka S that adds two new data types for the properties: geometry and geography. It allows to manage points and areas on images and maps. It uses the WKT format and can use an external database.

It is used by the module Annotate Cartography, that allows to point markers and to highlight images and maps. This module can be used independantly too.

Installation

Libraries

The module uses external libraries, so use the release zip to install it, or use and init the source.

See general end user documentation for installing a module.

  • From the zip

Download the last release DataTypeGeometry.zip from the list of releases (the master does not contain the dependency), and uncompress it in the modules directory.

  • From the source and for development

If the module was installed from the source, rename the name of the folder of the module to DataTypeGeometry, go to the root of the module, and run:

    npm install
    composer install
    gulp

Omeka database or external database [work in progress]

The geometries can be saved in Omeka database or in an external one. It’s useful to share them with other GIS systems. It allows to do advanced search and to browse quicker too.

So the database must support spatial indexing. It must be equal or greater than MariaDB 10.2.2 (2016-09-27) or mySql 5.7.5 (2014-09-25), for the engine InnoDB. Prior database releases can support spatial index too, but only with the engine MyIsam (that does not support referential integrity and is not used by Omeka). The choice between InnoDB and MyIsam is done automatically.

To support searches of geometres, (distance around a point, geometries contained inside another geometry), the version of should be minimum mySql 5.6.1 (2011-02) or mariaDB 5.3.3 (2011-12-21). Note that the minimum Omeka version is mySql 5.5.3 (2010-03-24, equivalent to MariaDB 5.5.20 (2012-02-25)), so some releases of mySql are below the minimum requirement of this module. For a precise support of geometry, see the spatial support matrix.

You may prefer to use an external database. To config it, set the parameters in the file config/database-cartography.ini, beside your main config/database.ini. See the file config/database-cartography.ini.dist for more information. The tables are named data_type_geometry and [data_type_geography]. Furthermore, if PostgreSql is used, the config/local.config.php should indicate it in [entity_manager][functions][numeric], by overriding keys of the mysql functions.

The support for MariaDB, mySql and PostgreSql is provided though doctrine2-spatial.

Configuration

Geometry

Geometries are WKT data: POINT (2.294497 48.858252).

The geometries are saved as standard Omeka values and indexed in a specific table with a spatial index for quick search.

Warning: The geometry "Circle" is not managed by WKT or by GeoJSON, but only by the viewer. It is saved as a POINT in the database, without radius.

Only common sql spatial functions are enabled. Other ones can be enabled in the config of the module (via local.config.php).

Geography

Geography is a second data type to manage geographic data. It is the same than the geometry above, but an additional spatial referentiel identifier (srid) is saved, so the geometries are georeferenced. It allows to do precise searches on the Earth, in particular when the distances are longer than some dozen of kilometers.

Most of the time, the srid is 4326, because it’s the Mercator projection used by default in many geographic systems and by OpenStreetMap, the most truely open layer used for the web geolocation and by the module Annotate Cartography. Another value can be set in the main settings, and each value can set a specific one with the ewkt format: SRID=4326; POINT (2.294497 48.858252). It is not recommended to set it when it is the default one.

Warning: The data type Geography doesn’t support complex geometries ( multipoint, multiline and multipolygon). In that case, it’s recommended to use collections.

JSON-LD and GeoJSON

According to the [discussion] on the working group of JSON-LD and GeoJSON, the GeoJson cannot be used in all cases inside a JSON-LD. So the representation uses the data type http://www.opengis.net/ont/geosparql#wktLiteral of the OGC standard. The deprecated datatype http://geovocab.org/geometry#asWKT is no more used.

{
    "@value": "POINT (2.294497 48.858252)",
    "@type": "http://www.opengis.net/ont/geosparql#wktLiteral"
}

TODO

  • Remove doctrine:lexer from composer vendor.
  • Use the sub-types of geometries and use them eventually in a specific table (the database engine can manage the generic geometry or each particular type).
  • Add a js to convert wkt into svg icon (via geojson/d3 or directly).

Warning

Use it at your own risk.

It’s always recommended to backup your files and your databases and to check your archives regularly so you can roll back if needed.

Troubleshooting

See online issues on the module issues page on GitHub.

License

This module is published under the CeCILL v2.1 licence, compatible with GNU/GPL and approved by FSF and OSI.

This software is governed by the CeCILL license under French law and abiding by the rules of distribution of free software. You can use, modify and/ or redistribute the software under the terms of the CeCILL license as circulated by CEA, CNRS and INRIA at the following URL "http://www.cecill.info".

As a counterpart to the access to the source code and rights to copy, modify and redistribute granted by the license, users are provided only with a limited warranty and the software’s author, the holder of the economic rights, and the successive licensors have only limited liability.

In this respect, the user’s attention is drawn to the risks associated with loading, using, modifying and/or developing or reproducing the software by the user in light of its specific status of free software, that may mean that it is complicated to manipulate, and that also therefore means that it is reserved for developers and experienced professionals having in-depth computer knowledge. Users are therefore encouraged to load and test the software’s suitability as regards their requirements in conditions enabling the security of their systems and/or data to be ensured and, more generally, to use and operate it in the same conditions as regards security.

The fact that you are presently reading this means that you have had knowledge of the CeCILL license and that you accept its terms.

Libraries

This module uses many open source leaflet libraries. See asset/vendor for details.

Copyright

  • See asset/vendor/ and vendor/ for the copyright of the libraries.
  • Some portions are adapterd from the modules Numeric data types and Neatline.
  • Copyright Daniel Berthereau, 2018, (see Daniel-KM on GitHub)

This module was built first for the French École des hautes études en sciences sociales EHESS.