Meta Raster Format (MRF) Reader Parameters

  • From File Name(s): Generates one feature type per source filename. If this mode is selected, each raster of the MRF will be read, including individual pyramid levels. For example, an MRF with 5 levels and 7 pyramid levels will output 35 features.
  • From Format Name: Produces only a single feature type containing the format name. If this mode is selected, each raster of the MRF will be read, including individual pyramid levels. For example, an MRF with 5 levels and 7 pyramid levels will output 35 features.
  • From Subdataset Name(s): Generates one feature type per subdataset in the MRF. An MRF will have one subdataset for each Z-Slice and Pyramid level combination. For example, an MRF with 10 Z-Slices and 6 pyramid layers will have 60 subdatasets.
  • From File Name(s) and Subdataset Name(s): FeatureType names match the above but with the prefix [rootFileName]_.

An MRF is composed of an arbitrary number of three-dimensional layers, referred to as Z-Slices, which are additional rasters of the same size and number of bands that are stored in the same data file. Each of these rasters also has its own Pyramid Levels.

Use this parameter to specify which Z-Slices to read. For example, Z0 or YourFile_Z0 means that the reader will read from Z-Slice 0.

  • If Feature Type Name(s) is set to From File Name(s), or From Format Name, the only option is to read the entire MRF dataset.
  • If Feature Type Name(s) is set to Subdataset Name(s), or File Name(s) and Subdataset Name(s)

Use this parameter to specify which pyramid level to read. This pyramid level will be read at each Z-Slice specified in the list (when applicable). Specifying a value of 3 will read pyramid level 3 from all of the Z-Slices specified.

The Pyramid Levels are progressively less resolute versions of the base level. Pyramid Level 0 refers to the original image stored at a given Z-Slice, and does not contribute to the total number of pyramid levels contained in an MRF.

For example, if an MRF has 10 Z-Slices and 5 pyramid levels, the MRF is a datafile that stores 10 x 6 individual rasters.

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).

Advanced

Pyramid Level to Read

This parameter specifies the pyramid level from which to read.

Pyramid level 0 represents the original raster data. Values greater than 0 represent increasingly reduced levels of image resolution.

Each pyramid level has half the number of rows and columns of the previous level.