Spectral Linear Combination module

Name	Caption
Input Scenes	Input scene folder
Output Folder	Output folder
Output File Type	Output file type
Output File Options	Output file options
Overwrite Results	Overwrite existing results
Send Email	Email notification settings
Source Background Type	Source background type
Source Background Value	Source background pixel value
Input Raster Channels	Input raster channels to process
Coefficients Source	Source of linear-combination coefficients
List	List of linear-combination coefficients
File	Text file of linear-combination coefficients

Parameter descriptions

Input Scenes

The path and name of the folder containing the scenes of orthorectified images to process.

This parameter is mandatory.

Output Folder

The path and name of the folder to which to write the output files.

Output File Type

The format of the output file.

For more information on the supported file formats, see GDB-supported file formats.

Output File Options

The options to apply when creating the output file or files. The available options are specific to the file format; in each case, the default of no options is allowed.

For more information on the options available for the output file type you specify, see GDB-supported file formats.

Overwrite Results

Select this check box to overwrite the existing output files, if any exist. If this check box is left clear, and an output file exists in the relevant folder, the status of the job displays a message informing you of the existence and name of the output file. The message is also written to the event log of the job.

Send Email

If necessary, you can set up CATALYST Enterprise to send an email notification on job start and job completion.

With this check box selected, an email message is sent to each address specified in the Email Addresses box after the job starts and on completion.

You can specify one or more addresses, and each must be separated by a comma or a semi-colon. The email address of the user currently logged in displays by default.

Source Background Type

The method to use to determine which pixels in the source image to process as background (NoData) pixels. In general, if a pixel is considered NoData, the module processes it in a specific manner.

If the Any option or the All option is selected, a value must be specified for the Source Background Value parameter.

Available options are:

File Metadata, else None: reads the NoData value from the input-file metadata. The module first checks for the file-level metadata tag NO_DATA_VALUE in the source raster. If the tag is present, this value is used as a default for all channels in the file. Next, the module checks for channel-level NoData tags; if one is found, the channel-level value overrides the file-level value for that channel.

If there are channel-level NoData tags, but no file-level tag, a pixel is considered as NoData if each of the channels with a NoData tag corresponds to its NoData value. In this case, channels without a NoData tag are ignored when identifying background pixels.

If the file does not contain NoData tags, all pixels in the source image are considered valid.
None: all pixels in the source image are to be considered valid
All: if the pixel value in all channels matches the values provided for the Source Background Value parameter, the pixel is considered background (NoData).
Any: if the pixel value in any channel matches the value provided for the Source Background Value parameter, the pixel is considered background (NoData).

For specific examples, see the Source Background Value parameter description.

Source Background Value

The source background value or values when the Source Background Type parameter is set to:

The source background value is provided as either a single number (applied to all channels) or as a pixel "stack" (a comma-delimited list of values). If a pixel stack is provided, but the number of values does not equal the number of channels, the list is truncated or the last value is repeated as necessary. The background values provided is truncated to the range allowed by the source image data type.

The following examples apply to a 3-channel, 8-bit unsigned image:

Source Background Type set to All and Source Background Value set to 0: a pixel is considered background if all three channels are zero.
Source Background Type set to Any and Source Background Value set to 0: a pixel is considered background if any of the three channels is zero
Source Background Type set to All and Source Background Value set to 128,0,0: a pixel is considered background if its value is exactly 128 for the first channel and zero for the second and third channels
Source Background Type set to All and Source Background Value set to 128,0,0,245: a pixel is considered background if its value is exactly 128 for the first channel and zero for the second and third channels. The value 245 is ignored.
Source Background Type set to Any and Source Background Value set to 128,0: a pixel is considered background if the value in channel 1 is 128 OR if the value in channel 2 or 3 is zero.
Source Background Type set to Any and Source Background Value set to 1032,0: a pixel is considered background if the value in channel 1 is 255 OR if the value in channel 2 or 3 is zero. The first value is truncated to the range allowed for 8U data.

Input Raster Channels

For each orthorectified image scene, the channels to include in the linear combination.

If you do not specify a value, all channels in the scenes are used.

This parameter is optional.

Coefficients Source

The source of the coefficients you specify to apply to the orthorectified image scenes during processing.

You can select from the following:

List: When you select this item, enter the list of coefficients in the List box, below.
File: When you select this item, enter the path and file name in the File box, below.

List

When you select List for Coefficient Source, the linear-combination coefficients to apply to the orthorectified image scenes during processing.

You must provide coefficients for each input raster channel. Separate each coefficient set of an image channel with a semicolon (;). By default, all image raster channels are included.

The format for the list is as follows:

1.0,0.0,0.0,0.0; 0.0,0.91,0.0,0.09; 0.0,0.0,1.0,0.0; 0.0,0.0,0.0,1.0

In the preceding example, a unique set of coefficients for four image channels is specified. The order of the coefficient sets follows the order of the image channels as observed in the input orthorectified image scenes. Typically, the order is as follows:

Blue
Green
Red
Near infrared (NIR)

File

When you select File for Coefficient Source, the path and file name of the linear-combination coefficients to apply to the orthorectified image scenes during processing.

You must specify the coefficients for each input raster channel on a separate line, as shown in the following figure:

In the preceding figure, a text file shows a unique set of coefficients specified for four image channels, each on a separate line. The order of the coefficient sets follows the order of the image channels as observed in the input orthorectified image scenes. Typically, the order is as follows:

Blue
Green
Red
Near infrared (NIR)

Details

General job details

Before running this module, the following requirements must be met to ensure the job processes successfully and produces accurate results:

Input image scenes must be orthorectified, either by running the Orthorectification module or by other means.

Module details

The Spectral Linear Combination module applies linear combination to the raster channels of orthorectified image scenes using the coefficients you specify. The linear-combination procedure mixes spectral information from various raster channels to create a new set of raster channels. The specified coefficients represent the portion of the image channel or channels to add to the new raster channel.

For example, to create a linear combination composed of 91 percent of channel 2 (green) and nine percent of channel 4 (NIR), select List for Coefficients Source, and then in the List box, enter the following:

0.0,0.91,0.0,0.09

The formula used in the calculation is as follows:

Channel 1 (blue) × 0.0 + channel 2 (green) × 0.91 + channel 3 (red) × 0.0 + channel 4 (NIR) × 0.09

Job results

For each valid orthorectified image scene in the input folder, the Spectral Linear Combination module creates a spectral linear combination child job. Each output image contains the newly computed raster channels from the linear-combination process. The names of the output image files are the same as those of the input and written to the specified output folder.

You can open the processed scenes in CATALYST Professional Focus to perform quality assurance (QA).

Spectral Linear Combination module

Description

Parameters

Parameter descriptions

Details