# NextGIS Web

NextGIS Web - is a server GIS, which allows to store and edit geodata and to display maps in web browser. Also NextGIS Web can share geodata with other NextGIS software.

NextGIS Web has the following features:

- Display maps in a web browser (different maps with different layers and styles)
- Flexible permissions management
- Load geodata from PostGIS or import from GIS formats (ESRI Shape, GeoJSON or GeoTIFF)
- Load vector geodata in the following formats: GeoJSON, CSV, ESRI Shape
- Import map styles from QGIS project or set them manually
- Act as a server for TMS, WMS, WFS
- Act as a client for WMS
- User can add photos to records, change record attributes via web interface or WFS-T protocol

NextGIS Web - is an open source software (license GPL v2+, see GNU General Public License, version 2).

## Driver

The driver is available since GDAL/OGR >= 2.4. NextGIS Web supports several raster types:

- Raster style
- Vector style
- WMS layer
- WMS Service
- Web map as combination of raster and vector styles

Each NextGIS Web raster layer can have one or more raster styles.
Each NextGIS Web vector or PostGIS layer can have one or more vector style (QGIS qml or MapServer xml).
WMS layer is one or more layers from external WMS service. This layer has no styles.
WMS Service is usual WMS protocol implementation.

Now NGW driver supports only raster and vector styles and WMS layers. You can get raster data as tiles or image (only tiles are supported now).

The driver supports read-only operations on rasters.

## Dataset name syntax

The minimal syntax to open a NGW datasource is: NGW:[NextGIS Web URL][/resource/][resource identifier]

- NextGIS Web URL may be an url to nextgis.com cloud service (for example, https://demo.nextgis.com), or some other url including port and additional path (for example, http://192.168.1.1:8000/test).
- resource is mandatory keyword dividing resource identifier from the rest of URL.
- resource identifier this is positive number from 0 and above. This may be a resource group, vector, PostGIS or raster layer, style.

If identifier is resource group, all vector layers, PostGIS, raster layers, styles will be listed as child resources. In other case this will be a separate raster.

## Configuration options

The following configuration options are available:

- NGW_USERPWD: User name and password separated with colon. Optional and can be set using open options.
- NGW_CACHE_EXPIRES: Time in seconds cached files will stay valid. If cached file expires it is deleted when maximum size of cache is reached. Also expired file can be overwritten by the new one from web. Defaults to 604800 (7 days).
- NGW_CACHE_MAX_SIZE: The cache maximum size in bytes. If cache reached maximum size, expired cached files will be deleted. Defaults to 67108864 (64Mb).

## Authentication

Any operations (read, write, get metadata, change properties, etc.) may require an authenticated access. Authenticated access is obtained by specifying user name and password in open, create or configuration options.

## Open options

The following open options are available:

- USERPWD - Username and password, separated by colon.
- CACHE_EXPIRES=604800 - Time in seconds cached files will stay valid. If cached file expires it is deleted when maximum size of cache is reached. Also expired file can be overwritten by the new one from web. Defaults to 604800 (7 days).
- CACHE_MAX_SIZE=67108864 - The cache maximum size in bytes. If cache reached maximum size, expired cached files will be deleted. Defaults to 67108864 (64Mb).

## Metadata

NextGIS Web metadata are supported in datasource, vector, PostGIS, raster layers and styles. Metadata are stored at specific domain "NGW". NextGIS Web supported metadata are strings and numbers. Metadata keys with decimal numbers will have suffix .d and for real numbers - .f. To create new metadata item, add new key=value pair in NGW domain use the SetMetadataItem function and appropriate suffix. During transferring to NextGIS Web, suffix will be omitted. You must ensure that numbers correctly transform from string to number.

Resource description and key map to appropriate description and keyname metadata items in default domain. Changing those metadata items will cause an update of resource properties.

Resource creation date map to read-only metadata item creation_date in default domain.

Vector layer field properties (alias, identifier, label field, grid visibility) map to layer metadata the following way:

- field alias -> FIELD_{field number}_ALIAS (for example FIELD_0_ALIAS)
- identifier -> FIELD_{field number}_ID (for example FIELD_0_ID)
- label field -> FIELD_{field number}_LABEL_FIELD (for example FIELD_0_LABEL_FIELD)
- grid visibility -> FIELD_{field number}_GRID_VISIBILITY (for example FIELD_0_GRID_VISIBILITY)

## Examples

Read datasource contensts:

        gdalinfo NGW:https://demo.nextgis.com/resource/1730

Read raster details:

        gdalinfo NGW:https://demo.nextgis.com/resource/1734

### See also:

- NextGIS Web documentation
- NextGIS Web for developers