Web Map Service (WMS)

The OpenGIS® Web Map Service Interface Standard (WMS) provides a simple HTTP interface for requesting geo-registered map images from one or more distributed geospatial databases. A WMS request defines the geographic layer(s) and area of interest to be processed. The response to the request is one or more geo-registered map images (returned as JPEG, PNG, etc) that can be displayed in a browser application. The interface also supports the ability to specify whether the returned images should be transparent so that layers from multiple servers can be combined or not.

The standard can be obtained from the Open Geospatial Consortiums homepage.

The following tables provide an overview over the available WMS request parameters for each operation supported by EOxServer.

GetCapabilities

Table: “WMS GetCapabilities Request Parameters” below lists all parameters that are available with Capabilities requests.

WMS GetCapabilities Request Parameters

Parameter

Description / Subparameter

Allowed value(s) / Example

Mandatory (M) / Optional (O)

service

Requested service

WMS

M

request

Type of request

GetCapabilities

M

acceptVersions 1

Prioritized sequence of one or more specification versions accepted by the client, with preferred versions listed first (first supported version will be used) version1[,version2[,…]]

1.3.0, 1.1.0, 1.0.0

O

updateSequence

Date of last issued GetCapabilities request; to receive new document only if it has changed since

“2013-05-08”

O

GetMap

Table: “WMS GetMap Request Parameters” below lists all parameters that are available with GetMap requests.

WMS GetMap Request Parameters

Parameter

Description / Subparameter

Allowed value(s) / Example

Mandatory (M) / Optional (O)

service

Requested service

WMS

M

request

Type of request

GetMap

M

version

Version number

1.3.0, 1.1.0, 1.0.0

M

layers

The layers to render. Must be a comma-separated list of layer names. Exposed layers are listed in the Capabilities document and depend on the contents of the instance.

For each object in the database a base layer with the objects identifier as a name is added. Additionally a number of layers are added with the objects identifier plus a postfix as show in the list below:

  • all:

    • <no-postfix>: the default rendering of the object

    • outlines: the objects footprint as a rendered geometry

    • outlined: the default rendering of the object overlayed with the objects rendered footprint.

  • Collection/Product:

    • <mask-name>: the rendered mask geometries for all products in that collection or that single product.

    • masked_<mask-name>: the default rendering of each product, each individually masked with the mask of the provided mask-name.

    • <browse-type-name>: renders the product(s) according to the browse types instructions (or uses an already existing browse if available.

M

styles

The style for each of the rendered layers to be rendered with. This must be either empty or a comma-separated list of either empty strings or names of valid styles. When left empty (for a single layer or the whole parameter), the default styling is applied.

The available styles depend on the layer type. Outline and mask layers can be rendered in the basic colors. Single band output can be styled using a range of color scales.

The Capabilities document lists the available styles per layer.

M

format

Requested format of the map to be returned, currently:

  • image/tiff

  • image/jpeg

  • image/png

  • image/gif

image/tiff

M

bbox

The bounding box of the output map. Depending on the service version and the coordinate reference system, the axis order might change. The following rules apply:

  • for service version 1.3 the axis order of the used CRS applies. For EPSG:4326, for example, the axis order is lat, lon, resulting in bounding boxes like <min_lat>,<min_lon>,<max_lat>,<max_lon>

12,17,14,17.4

M

crs / srs 1

The CRS the bbox values are expressed in.

EPSG:4326

M

width

The width of the output image in pixels.

512

M

height

The height of the output image in pixels.

512

M

bgcolor

The background color to use in HEX notation: RRGGBB

000000

M

transparent

Defines whether or not to use transparency for non-colored regions of the image. The format must provide an alpha channel (like PNG).

TRUE

M

dim_bands

Selects the given bands as gray, RGB or RGBA channels.

B04,B03,B02

O

dim_wavelengths

This behaves the same as with dim_bands but allows to specify the bands center wavelength instead of the bands name

664.6,559.8,492.4

O

dim_range

Allows to specify a min/max value for each selected band linearly interpolate values.

0 1;0 1;0 5

O

cql

Allows to specify metadata filters. See the Common Query Language (CQL) documentation for usage.

cloudCover < 10

O

sortBy

Allows to sort the images regarding a specific metadata value. Can either be ascending or descending using A or D

cloudCover A

O

1(1,2)

For WMS service version 1.3 the crs parameter must be used, for services versions below 1.3 the parameter name is srs.

Layer Mapping

Various objects in EOxServer generate exposed layers to be requested by clients via WMS.

WMS Layer Mapping

Base Object

Suffix

Description

Style

Advertised [2]

Coverage

Renders the coverage as a map. This is the most basic for of rendering and dim_bands and dim_range will likey need to be used to achieve representative result.

When the coverage only has a single field, or only one is selected via dim_bands, then the name of a color scale can be passed to colorize the otherwise greyscale image.

no

Mosaic

This behaves exactly like with Coverages but applies the rendering to all contained Coverages.

Same as above.

yes

Product

Renders the Products default Browse or using the defaults Browse Type to dynamically render a browse.

no

Coverage/Product

outlines

Renders the footprint of the Coverage/Product as a colorized geometry.

Defines the color of the rendered geometry.

no

Mosaic/Collection

outlines

Renders the footprint of all contained Coverages or Products as a colorized geometry.

Defines the color of the rendered geometry.

yes

Coverage/Product

outlined

Renders the Coverage/Product in its default way (as with no prefix) but overlays it with the footprint geometry (as with outlines suffix)

Defines the color of the rendered geometry.

no

Mosaic/Collection

outlined

Renders the Mosaic/Collection in its default way (as with no prefix) but each included Coverage/Product rendering is overlayed with the footprint geometry (as with the outlines suffix).

Defines the color of the rendered geometry.

yes

Product

<Browse Type Name>

Renders the Products Browse of that Browse Type if available or uses the Browse Type to dynamically render a Browse.

no

Product

<Mask Type Name>

Renders the Mask of the Product of that Mask Type as a rasterized vector layer.

Defines the color of the geometry.

no

Product

masked_<Mask Type Name>

Use the default rendering of the product and apply the Mask of the specified Mask Type.

no

Collection

Renders all Products in the Collection with their default Browse (or dynamically using the default Browse Type).

Collection

<Browse Type Name>

Renders all contained Products using the Browse of that Browse Type or dynamically generated Browse of that Browse Type.

Collection

<Mask Type Name>

Renders all Masks of the contained Products as colorized geometries.

Collection

masked_<Mask Type Name>

Renders all contained Browses using their default Browse or a dynamically generated Browse of the default Browse Type and individually apply the Mask of that Mask Type.

2

Whether or not this layer is by default advertised in GetCapabilities documents. This can be overridden by setting the objects visibility.