OGC Web Map Service (WMS) Reader Parameters

WMS Connection

The URL for the WMS server. A typical URL specifying a WMS server looks like

http://www.fmeserver.com/wms

HTTP Authentication

Use Network Authentication

Note  This parameter is always visible in some formats, and visible in other formats only when the dataset is a URL.

Authentication Method

Specify the authentication method to use when accessing a password-protected server.

  • Basic (default) – Basic access authentication is designed to allow a client to provide credentials to a server on the assumption that the connection between them is trusted and secure. Note that any credentials passed from client to server can be easily intercepted through an insecure connection.
  • Digest – Digest authentication is one of the agreed-upon methods a web server can use to negotiate credentials, such as username or password, with a user's web browser.
  • NTLM – A challenge-response protocol that is used to provide compatibility with versions of Windows earlier than the Windows 2000 operating systems.
  • Web Connection – Web connections provide a convenient and secure way to store and reuse previously established connection parameters. See Web Connection below.
  • Single Sign-on – FME will use the credentials of the current user to authenticate the HTTP request. This authentication method currently works only on the Windows operating system.
Note  To access datasets using a proxy server, use the Network tools in FME Options. From the FME Workbench menu, select Tools > FME Options > Network. For more information, see "Network Proxy" in FME Workbench Help.

Web Connection

Using Web Connections

FME Options: Web Connections

Constraints

After you have completely specified the connection, click the Browse button to select layers for import. A connection window appears while the system compiles a table from the database. Once the layer list appears, you can select one or more layers, and then click OK to dismiss the window. The layer name(s) will appear in the layer list field in the Reader Parameters box.

When selected, instructs the WMS reader to split the selected layers into separate HTTP Get Requests. That is, if N layers are selected, then N separate HTTP GetMap requests are performed fetching N images.

Map Options

Sets the background transparency for a map. When this option is selected, and the image format supports transparency (e.g., PNG and GIF), the map server will send an image with transparent background.

Specifies the width in pixels for the image.

Specifies the height in pixels for the image.

Specifies the image output format as a MIME type. The output format must be one of the formats listed in the WMS capabilities document. The directive defaults to “image/png”.

Specifies the desired coordinate system. The default value is “CRS:84” for WMS 1.3.0 and “EPSG:4326” for WMS 1.1.0 and 1.1.1.

Time value or range for map data, expressed using any of the following syntaxes:

Syntax Meaning
value A single value.
value1,value2,value3,... A list of multiple values.
min/max/resolution An interval defined by its lower and upper bounds and its resolution.
min1/max1/res1,min2/max2/res2,... A list of multiple intervals.

Elevation value or range for map data, expressed using any of the following syntaxes:

Syntax Meaning
value A single value.
value1,value2,value3,... A list of multiple values.
min/max/resolution An interval defined by its lower and upper bounds and its resolution.
min1/max1/res1,min2/max2/res2,... A list of multiple intervals.

Additional Attributes to Expose

Use this parameter to expose Format Attributes in FME Workbench when you create a workspace:

  • In a dynamic scenario, it means these attributes can be passed to the output dataset at runtime.
  • In a non-dynamic scenario, this parameter allows you to expose additional attributes on multiple feature types. Click the browse button to view the available format attributes (which are different for each format) for the reader.
 

A search envelope (also known as a bounding box) is a rectangular area that defines a geographic area. In FME, the easiest way to define a search envelope is to use search envelope parameters.

Defining a search envelope is the most efficient method of selecting an area of interest because FME will read only the data that is necessary – it does not have to read an entire dataset. Search Envelope parameters apply to both vector and raster datasets and can be particularly efficient if the source format has a spatial index.

Most FME readers have parameters to define the search envelope of data that is being read:

Screenshot with blank search envelope min and max x and y parameters

The parameters include the x and y coordinates of the bounding box as well as a parameter that defines the coordinate system.

How to Define the Bounding Box

Using the minimum and maximum x and y parameters, define a bounding box that will be used to filter the input features. Only features that intersect with the bounding box are returned. Note that the bounding box intersection is not a full geometry intersection (based on spatial relationships) that would be returned by a transformer like the SpatialFilter.

Note  If all four coordinates of the search envelope are left at 0, the search envelope will be disabled even if this option is checked.

Search Envelope Coordinate System

Specifies the coordinate system of the search envelope if it is different than the coordinate system of the data. The coordinate system associated with the data to be read must always be set if this parameter is set.

If this parameter is set, the minimum and maximum points of the search envelope are reprojected from the Search Envelope Coordinate System to the reader’s coordinate system prior to applying the envelope.

Clip to Search Envelope

The underlying function for Use Search Envelope is an intersection; however, when Clip to Search Envelope is checked, a clipping operation is also performed.

  • When left unchecked (set to No), features that overlap the boundary will be included in their full (unclipped) form.
  • When checked (set to Yes), this option instructs FME to clip features to the exact envelope boundary. FME removes any portions of imported features being read that are outside the search envelope.

Clip to Search Envelope: No

Clip to Search Envelope: Yes

Any features that cross the search envelope boundary will be read, including the portion that lies outside of the boundary.

Any features that cross the search envelope boundary will be clipped at the boundary, and only the portion that lies inside the boundary will be read.

The search envelope includes the bounding box and the extent of the raster.

The search envelope includes only the area within the bounding box.

The raster size will still match the bounding box, but the area without data will be filled with Nodata values to represent the absence of data, if the source raster has them.

Raster Nodata may be a single value across all bands, a single value per band, or a separate alpha or transparency band that indicates the lack of data values (this is more common in images than other types of rasters).