Orthorectification module

Name	Caption
Input Scenes	Input 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
Output Background Value	Output background value
DEM Source	DEM tile source
Output Map Units	Output projection
Panchromatic Pixel Output Size	Panchromatic output pixel size
Multispectral Pixel Output Size	Multispectral output pixel size
Resampling Method	Resampling method
Resampling Method Extra Options	Extra options for resampling method
Raster Channels	List of channels
Sampling Interval Range	Range from sampling interval is selected
Alignment Position	Relative alignment position to the first pixel in the orthorectified image
Alignment Extra Options	The stride of alignment grid and reference points

Parameter descriptions

Input Scenes

The path and name of the folder containing raw images that include a valid math-model segment. Images in this folder must have been processed previously with one of the modules in the following table, depending on whether points have been collected.

When	Specify Input Scenes as
No points have been collected	Path and name of the output folder of the Data Ingest module
Only ground control points (GCPs) have been collected	Path and name of the output folder of the GCP Collection module
Only tie points (TP) have been collected	Path and name of the output folder of the Tie-Point Collection and Refinement module
Only GCPs and TPs have been collected	Path and name of the output folder of the Tie-Point Collection and Refinement module

This parameter can be specified by using any of the following:

Path and name of a folder of input images; for example, C:\data
Path and name of a folder containing an OrthoEngine project file; for example, C:\data\data-ingest_RAW_PAN.prj
Path and name of a folder with a wildcard to filter the imagery by file name or type; for example, C:\data\*_PAN.pix
Path and name of a folder path with a wildcard to filter by OrthoEngine project file; for example, C:\data\*_PAN.prj
You can also specify an MFILE as input. An MFILE is a text file with an .mfile file name extension. For more information on this type of file, see About the MFILE format.

Output Folder

The path and name of the folder in which to write the output orthorectified image scenes.

Output images are created using a file name generated automatically that includes the image scene, state, and image type.

Note: When the output folder is on another computer on your network, the orthorectified imagery is created temporarily in a local temporary folder, and then copied to the specified output folder; the local copy is then deleted.

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.

Output Background Value

The background (NoData) value to use for pixels that are not populated.

The specified background value is truncated to the range allowed by the source image data type.

When you specify one value, all channels are set to the same NoData value. If you want to specify different values for various channels, separate the values with commas. For example, to specify -32768 for channel 1 and zero for channel 2 (and any subsequent channels), enter "-32768, 0".

DEM Source

The name of a single digital elevation model (DEM) file or a folder containing one or more DEM tiles.

This parameter can be specified by using any of the following:

Name of a single DEM file; for example, C:\data\DEM\dem.pix
Name of a folder containing one or more DEM tiles and an associated index.txt file; for example, C:\data\DEM
Name of an index file; for example, C:\data\DEM\index.txt

The index.txt file lists the DEM files contained in the specified folder and provides information describing each DEM tile. The information in the DEM index file supersedes other DEM parameters in the module; all other DEM-related parameters are ignored. For more information about the format of the index.txt file and specific requirements for the individual DEM tiles, see Format of the DEM index file.

When the value of DEM Source is the name of an existing folder, the module searches that folder for a file named index.txt, and a set of DEM raster tiles. The index.txt file contains a single vector channel that lists the DEM files contained in the specified folder and provides information describing each DEM tile.

Output Map Units

The projection of the output imagery.

The value of this parameter must be in the PCI Projection String format.

The standard definitions are:

PIXEL: Pixel and line (not for use with DEM extraction)
UTM: Universal Transverse Mercator

The value specified can be the UTM grid zone number and row, and Earth model, as follows:
```
UTM [mm] [r] [Ennn]
```
where:
- [mm] is the two-digit zone number between 1 and 60
- [r] is the zone row: a single letter between N and X for north of the equator and between C and M for south of the equator. Zone rows A, B, Y, and Z are not supported; rows I and O do not exist.
- [Ennn] specifies the Earth model, where the model number is between 0 and 19. If the Earth model is not specified, it is assumed to be E000 (Clarke 1866).
SPCS: State Plane Coordinate System

The SPCS zone number and Earth model can be specified as follows:
```
SPCS [mmmm] [Ennn]
```
where:
- [mmmm] is the four-digit zone number
- [Ennn] specifies the Earth model, where the model number is between 0 and 19. If the Earth model is not specified, it is assumed to be E000 (Clarke 1866).
LONG/LAT: Longitude and latitude

The Earth model can be specified for LONG/LAT (and other units except PIXEL), as follows:
```
LONG/LAT [Ennn]
```
If the Earth model is not specified, it is assumed to be E000 (Clarke 1866).
EPSG: European Petroleum Survey Group code

You can specify the projection by entering an EPSG code defined by the Open Geospatial Consortium (OGC). For information on the code definitions, visit epsg.org and spatialreference.org.

The EPSG code is specified using the EPSG keyword followed by an integer and separated by a colon; for example:
```
EPSG:4326
```
Most common EPSG codes are supported.
METER: Image along-row and along-column meters
FEET: Image along-row and along-column feet
You can also specify the label of a projection you define, if the projection exists in the userproj.txt file; otherwise, you must enter the projection-parameter information as a string separated by the vertical bar (|). The projection-parameter string defines 18 parameters delimited by spaces, including the following:
- Dearth
- RefLong
- RefLat
- StdParallel1
- StdParallel2
- FalseEasting
- FalseNorthing
- Scale
- Height
- Long1
- Lat1
- Long2
- Lat2
- Azimuth
- LandsatNum
- LandsatPath
- UnitsCode
For example, the projection named 'France93' can be specified, as follows:
```
LCC D350 | 0 0 3.0 46.5 44.0 49.0 700000 6600000 0 0 0 0 0 0 0 0 0 -1
```

If you do not specify a value for Output Map Units, the map unit of the input image is used for the output image. If the input data is a variety of map units, the map unit of each output image is that of its corresponding input image. In such a case, it is recommended that you specify the output map units.

You can also specify the label of a projection defined in the userproj.txt file.

Panchromatic Pixel Output Size

The output spatial resolution for the panchromatic imagery to be orthorectified.

The units for the pixel size must match the units selected for the Map Units parameter; for example, if the map units are specified as UTM, the panchromatic pixel output size is in meters.

If no value is specified for this parameter, the pixel output size is based on the input math model associated with each scene in the input-scenes folder.

Note: If the input files have been pansharpened previously, specify the output pixel size in the Multispectral Pixel Output Size parameter.

Multispectral Pixel Output Size

The output spatial resolution for the multispectral imagery to be orthorectified.

Note: When the input images have been pansharpened previously, use this parameter to specify the output resolution.

The units for the pixel size must match the units specified for the Map Units parameter; for example, if the value of Map Units is specified as UTM, the multispectral pixel output size is in meters.

If no value for this parameter is specified, the pixel output size is based on the input math model associated with each scene in the input-scenes folder.

Resampling Method

The resampling method to use during processing.

Available resampling options are:

Cubic: cubic convolution. This method determines the gray level from the weighted average of the 16 pixels closest to the specified input coordinates and assigns that value to the output coordinates. The resulting image is slightly sharper than one produced by bilinear interpolation, and it does not have the disjointed appearance produced by nearest-neighbor interpolation. This is the default value.
Nearest Neighbor: nearest-neighbor interpolation. This method identifies the gray level of the pixel closest to the specified input coordinates and assigns that value to the output coordinates. Although this method is the most efficient in computation time, it introduces small offsets in the output image. The output image may be offset spatially by up to half a pixel, which may cause the image to have a jagged appearance.
Bilinear: bilinear interpolation. This method determines the gray level from the weighted average of the four closest pixels to the specified input coordinates and assigns that value to the output coordinates. An image with a smoother appearance than nearest-neighbor interpolation is created, but the gray-level values are altered in the process, resulting in blurring or degraded image resolution.
Lagrange-4: four-point Lagrange interpolation
Lagrange-8: eight-point Lagrange interpolation
Sinc-8: eight-point sin(x)/x
Sinc-16: 16-point sin(x)/x
Average: Average resampler for creating downsampled products
Gaussian: Gaussian resampler
Median: Median resampler for creating downsampled products

Resampling Method Extra Options

When you specify a value for the Resampling Method parameter, you can use the Resampling Method Extra Options parameter to specify additional options. The available options are specific to the following resampling methods:

Sin(x)/x with an 8 x 8 window
Sin(x)/x with a 16 x 16 window
SHAPINGWINDOW=[sw],BETA=[beta]

where:

SHAPINGWINDOW specifies a window to attenuate the SINC coefficients to reduce resampling artifacts. The value can be KAISER, HAMMING, HANN, LANCZOS, PARABOLA, or NONE. SHAPINGWINDOW is optional; the default value is KAISER. BETA is applicable only when SHAPINGWINDOW is KAISER. SHAPINGWINDOW determines the shape of the KAISER window; a larger BETA value produces greater attenuation of the SINC coefficients. Its value can be between 1.0 and 10.0. BETA is optional.

Average
NUMCOLS=[nc],NUMROWS=[nr]
Median
NUMCOLS=[nc],NUMROWS=[nr]

where:

NUMCOLS and NUMROWS can be any value between 1 and 11.
Gaussian
DSFACTORCOL=[dc],DSFACTORROW=[dr]

where:

DSFACTORCOL is the fraction downsampling factor in col (>=1). If not specified, a default factor is computed automatically based on the output and input pixel sizes. DSFACTORROW is the fraction downsampling factor in row (>=1). If not specified, default to the value of DSFACTORCOL.

Note: With each resampling method, the parameters MIN=[min], MAX=[max], and FILL=[NN or BGD] can be appended as a comma-delimited list. MIN and MAX define the clamp range for output pixels. This is useful when you want to keep pixel values within a certain range; for example, 1 to 2047 if 11-bit data is stored in a 16-bit file. FILL defines the behavior when the resampling window contains NoData pixels: NN instructs the resampler to use the Nearest Neighbor method, while BGD indicates that the output pixel is set to the background value. By default, NN is used for FILL.

Raster Channels

A comma-delimited list of channels; for example, 1,2,5.

This parameter is optional. If you do not specify a value, all of the channels in the input files is used.

Sampling Interval Range

The range from which the sampling interval is selected. The range consists of two values: a minimum and maximum sampling interval. When you specify a range, the sampling interval is calculated based on the ratio of the resolution of the digital elevation model (DEM) and that of the output orthorectification.

When you specify only a single value, the value is used as the sampling interval and not calculated.

Example 1:

Sampling Interval Range = 1, 4
DEM resolution     = 10m
Ortho resolution   =  5m
Ratio = 2
Sampling Interval = 2

Example 2:

Sampling Interval Range = 2, 6
DEM resolution     = 1m, 1m
Ortho resolution   = 0.1m, 0.2m
Ratio = 10, 5
Sampling Interval = floor((0.1+0.2) / 2) = 7.5
Final Sampling Interval = 6 (because maximum in range forces to 6)

Example 3:

Sampling Interval Range = 2, 4
DEM resolution     = 1m, 1m
Ortho resolution   = 5m, 5m
Ratio = 1/5, 1/5
Sampling Interval = floor((1/5+1/5) / 2) = 0
Final Sampling Interval = 4 (because minimum in range forces to 4)

The sampling interval is the pixel spacing at which the math model is evaluated to determine the source raster location of the orthorectified pixel. A value of 1 performs a rigorous calculation on each output pixel.

With sampling intervals of 2 or greater, the intermediate pixels are the projection from the image to the Earth surface and is approximated by linearly interpolating it from the nearest locations at which the full orthorectification operation was performed.

A value of 1 is suitable in most situations. With math models that are more computationally intensive, a higher value can improve performance, but is at the expense of accuracy. The amount of loss of accuracy depends on the viewing geometry, resolution of the digital elevation model (DEM), and roughness of the DEM. When the area of interest features rugged areas, a higher value may degrade the detail of the terrain correction.

Alignment Position

By specifying an adjustment you can generate orthorectified images that fall on a specific raster grid.

Select the keyword indicates the relative positioning of the values:

CORNER: indicates that the values are relative to the upper-left corner of the first pixel in the output file.
CENTER: indicates that the values are relative to the center of the first pixel in the output file.

Alignment Extra Options

After you select the keyword for Alignment Position parameter, you can enter up to four values, as follows:

Stride_X
Stride_Y
Ref_X
Ref_Y

These values define the position of the corner or center in the raster grid.

Of the four values, only Stride_X is required. If not specified, Stride_Y defaults to the Stride_X value, and Ref_X and Ref_Y default to zero.

In the following example, the upper-left corner of the upper-left pixel of each tile is an even 20-meter multiple from the reference point (432345.000, 5438882.000). Depending on the distance of the tile from that point, its upper-left corner coordinate could be 432345.000, 432045.000, or any other multiple, but is never 432346.000 or 432355.000.

Example:

"CORNER, 20, 20, 432345.000, 5438882.000"

If specified, this parameter is applied in all scenarios, whether the image-corner coordinates come from the input file (MFILE), ULX and ULY, or through automatic computation.

Details

General job details

Preprocessing requirements

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

Math models: The imagery specified for orthorectification must contain a valid math-model segment.
The math-model segment can be:
- The nominal math-model segment, as imported with the raw data using the Data Ingest module
- A refined math-model segment created by the GCP Collection module or the Tie-Point Collection and Refinement module
- A refined math-model segment developed in OrthoEngine and exported to the imagery
Depending on the input imagery, however, not all images will contain a valid math model. For example:
- When a sensor is used in which the MS and PAN images are coregistered directly from the sensor (for example, IKONOS, QuickBird) and the MS and PAN files are present, the Orthorectification module automatically reads the math model in the PAN file, and automatically computes the corresponding rational functions model for the MS scenes. This is because there is a direct and established relationship between the rational-function coefficients for PAN and MS data sets. When the math models are computed, both image types are then orthorectified automatically.
- When the sensor being used does not have a direct relationship mapping the panchromatic rational-function coefficients to the multispectral rational-function coefficients (as with SPOT 5), and both MS and PAN files are present, the Orthorectification module automatically orthorectifies the PAN image first, then performs automated GCP collection routines to coregister the MS image to the PAN image. Finally, the MS image is orthorectified. When a stereo scene has multiple files, such as nadir, backward, or forward, the nadir panchromatic image will be selected for coregistration.
Imagery: The specified input imagery must have been ingested into CATALYST Enterprise with the Data Ingest module. This ensures that the imagery can be read by subsequent CATALYST Enterprise processes, and that the input files adhere to the CATALYST Enterprise file-naming convention.
Digital elevation models: A digital elevation model (DEM) is required to perform orthorectification. The specified DEM must be in a GDB-compatible format and should cover the full extents of the imagery requiring orthorectification. To ensure a highly accurate orthorectified image product, the DEM should be as accurate as possible. The DEM can be supplied as a single file, or a folder of individual DEMs.
File-naming convention: The module reads the input scenes folder for images containing the term "_RAW"; a tag created by the Data Ingest module. If this tag is not present in the file names, the Orthorectification module will not orthorectify the imagery.

Module details

The Orthorectification module automatically orthorectifies and corrects image scenes that contain a valid math-model segment. Orthorectification is an essential process to any photogrammetric project because, after it is performed, you can relate features in the image to their actual locations on Earth. Orthorectification also provides you with a means to take measurements and make accurate decisions.

If you want to produce an image mosaic, you must have orthorectified image products. You can also create pansharpened imagery with the Orthorectification module. While in some cases it is possible to produce pansharpened imagery from raw satellite scenes, in most cases the multispectral and panchromatic image bands must be orthorectified; the Orthorectification module module makes this workflow possible.

The Orthorectification module supports processing using a graphics-processing unit (GPU) and multicore processors.

Job results

The results produced by the Orthorectification module vary, depending on the input data types; however, all output files generally contain "_ORTHO" in the output file name.

The output file-name format is:

<SCENE ID>_ORTHO_<DATA TYPE>.<extension>

where:

SCENE_ID: The scene ID of the image to be orthorectified
ORTHO: Indicates that the image is orthorectified
DATA_TYPE: Indicates the output data type (PAN, MS, PSH, or RGB)

The output files are orthorectified images, written to the specified output folder. If an input scene includes bitmap layers, and the output file type is PCIDSK, the first bitmap will be orthorectified and written to the output file.

Orthorectification module

Description

Parameters

Parameter descriptions

Details