Layer Types
Below is a brief description of the different types of layers and formats that can be used in the Geoportal.
GeoJSON
GeoJSON is an open standard format designed to represent simple geographic elements, along with their non-spatial attributes, based on JavaScript Object Notation. The format is widely used in web-based mapping applications as it allows for quick, lightweight, and straightforward data exchange. The format’s grammar is based on the Open Geospatial Consortium’s WKT standard, with geometries that can be of type point (addresses, locations, points of interest, etc.), lines (routes, roads, borders, etc.), polygons (countries, administrative units, cadastral plots, etc.), and collections of these types. GeoJSON uses a geographic coordinate reference system, WGS84, and units in decimal degrees.
The Geoportal allows loading GeoJSON layers through three different methods: - Directly from a file with GeoJSON format. - A web URL that returns a GeoJSON format. - A WFS service that returns a GeoJSON format.
Database Table
A database is a set of data that belong to the same context and are systematically stored for future use. On the other hand, the database table refers to the type of data modeling where data collected by any database management program is stored. Its general structure resembles the overall view of a table program. Tables can consist of two structures:
- Field: Corresponds to the column name. It must be unique and have an associated data type.
- Record: Corresponds to each row that makes up the table, where data and records appear.
QGIS Project
A file with the extension .QGS and XML notation that contains a project of the QGIS application. The Geoportal allows publishing these types of files directly.
Please refer to the QGIS application page for all available information.
Information
The Geoportal only supports the .QGS format and not the compressed .QGZ version.
WMS (Tiles)
WMS, the abbreviation for Web Map Service, produces dynamically referenced spatial data maps from geographic information. With this service, clients do not obtain the original data itself but a digital image that allows the representation of this data on the screen without the need to download it. This allows maintaining data security, confidentiality, and ownership without depriving its public use and allows remote access by integrating data from different sources.
WMS (Raster)
In this case, it would be similar to the previous one, but instead of having the service in tile format, the nature of the layer is raster.
TMS
TMS, the abbreviation for Tile Map Service, like WMS, provides a digital image from geographic data. However, in this case, it significantly increases the response speed, as it uses collections of pre-generated tiles or image portions at defined scale intervals.
Unlike TMS in Google format, TMS has the origin of the tiles in the lower-left corner.
TMS (Google)
Exactly the same as the TMS format, but with the origin of the tiles in the upper-left corner.
You can check the order of the tiles on this website: Tile Formats
WFS (GeoJSON)
WFS, the abbreviation for Web Feature Service, is a service that allows querying and retrieving vector data and the associated alphanumeric information. It also enables spatial and alphanumeric queries and manipulation of geometries.
The Geoportal allows publishing layers in WFS format as GeoJSON.
Raster Layers
The Geoportal administrator has a utility to generate WMS services from raster images. Any image format supported by GDAL and MapServer can be used, but for optimization purposes, it is recommended to use the TIFF format with the following properties:
- Compression: JPG
- Tiling: Yes
- PHOTOMETRIC format: YCBCR
- Image pyramid
You can create this image format following this guide: Optimizing TIFF