GXL-Satellite Mosaic Preparation. Training Guide

Transcription

1 GXL-Satellite Mosaic Preparation Training Guide Version 1.0 June 20, 2016

2 Copyright notice 2011 PCI Geomatics Enterprises, Inc. All rights reserved. Software copyrighted by: PCI Geomatics Enterprises, Inc. 90 Allstate Parkway, Suite 501 Markham, Ontario L3R 6H3 CANADA Telephone number: (905) The Licensed Software contain material that is protected by international Copyright Law and trade secret law, and by international treaty provisions, as well as by the laws of the country in which this software is used All rights not granted to Licensee herein are reserved to Licensor. Licensee may not remove any proprietary notice of Licensor from any copy of the Licensed Software. RESTRICTED RIGHTS Canadian Government Use, duplication, or disclosure is subject to restrictions as set forth in Public Works and Government Services Canada Supplemental General Conditions Licensed Software U.S. Government Use, duplication, or disclosure by the Government is subject to restrictions set forth in subparagraph (b)(3) of the Rights in Technical Data and Computer Software clause of DFARS or subparagraph (c)(1) and (2) of the Commercial Computer Software-Restricted Rights clause at 48 CFR as amended, or any successor regulations thereto. The Government agrees: (a) if the Licensed Software is supplied to the Department of Defense ( DoD ), the Licensed Software is classified as Commercial Computer Software and the Government is acquiring only RESTRICTED RIGHTS in the Software as that term is defined in Clause (c)(1)(ii) of the DFARS (48 CFR ); and (b) if the Licensed Software is supplied to any unit or agency of the United States Government other than DoD, the Government s rights in the Licensed Software will be as defined in Clause (c)(2) of Supplement to the FAR. PCI, PCI Geomatics, PCI and design (logo), Geomatica, Committed to GeoIntelligence Solutions, GeoGateway, FLY!, OrthoEngine, RADARSOFT, EASI/PACE, ImageWorks, GCPWorks, PCI Author, PCI Visual Modeler, and SPANS are registered trademarks of PCI Geomatics Enterprises, Inc. Sentinel is a registered trademark of SafeNet, Inc. Copyright (c) Info-ZIP. All rights reserved. InstallAnywhere is a registered trademark of Macrovision Corporation. All other trademarks and registered trademarks are the property of their respective owners. PCI Geomatics and Geomatica are registered trademarks of PCI Geomatics. The information in this document is subject to change without notice and should not be construed as a commitment by PCI Geomatics. PCI Geomatics assumes no responsibility for any errors that may appear in this document.

3 Contents Copyright notice... ii 1. Introduction Workflow and data flow Preparing images for mosaicking... 3 GXL-Satellite Mosaic Preparation i

4 Acknowledgement PCI Geomatics acknowledges Blackbridge Geomatics for providing the sample data used in this text book. The data used in this training manual remain the property of Blackbridge Geomatics, Inc. The user of this manual is granted a non-transferable right to use the data/imagery contained in the documents in a non-commercial manner. The user may not, and may not permit others to, use, reproduce, or distribute, in whole or in part, the material in the documents. ii GXL-Satellite Mosaic Preparation

5 List of figures Figure 1: The GXL-S workflow... 2 Figure 2 Create Mosaic Preparation Job... 3

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7 Introduction 1. Introduction The PCI GeoImaging Accelerator Satellite (GXL-S) is a powerful and specialized processing system that allows you to efficiently use distributed processing techniques, in combination with modern computer hardware and automated workflows, to produce high-quality image mosaics comprised of satellite imagery from various sensors. The GXL Mosaic Preparation module automatically performs all the necessary pre-mosaicking procedures required to produce a high-quality image mosaic. These procedures include: cutline generation color balancing image normalization scene order specification removal of clouds/haze/exclusion areas 1.1 Workflow and data flow Error! Reference source not found. illustrates the standard workflow for processing satellite imagery with the GXL system. GXL-Satellite Mosaic Preparation 1

8 Introduction Figure 1: The GXL-S workflow 2 GXL-Satellite Mosaic Preparation

9 Preparing images for mosaicking 2. Preparing images for mosaicking To begin a mosaic preparation process, you must first create and submit a GXL Mosaic Preparation job. To create a GXL Mosaic Preparation job: 1. From the JPS Administrator main Navigation Bar, click Create Job. From the list of available jobs to submit, select Mosaic Preparation. The job submission page for the module appears. Figure 2 Create Mosaic Preparation Job The following table briefly describes the workflow parameters for this module. For more detailed information about each parameter, refer to the Module Reference Web Help accessible through the JPS Administrator (Help). Workflow Parameter Mandatory / Description Input Scenes Mandatory Specifies the name of a folder, image file, or text file that contains the data to be used for mosaicking. All source images to be mosaicked must have the same projection, bit depth, and resolution. Output XML File Mandatory Specifies the path and file name of the output XML file that will contain all metadata and information related to the mosaic, including GXL-Satellite Mosaic Preparation 3

10 Preparing images for mosaicking Workflow Parameter Mandatory / Description color balancing coefficients, images to be mosaicked, image order (z-order), and normalization. The module also generates a series of auxiliary XML files that contain information pertinent to each scene included in the mosaic, as well as cutline information. No Data Value Specifies the pixel value to exclude from processing, for all channels. A pixel classified as No Data will not be considered for normalization, color balancing, or cutline generation. Sorting Method Default ly specifies the order in which the images will be sorted and added to the mosaic. Available options are: Sorting Method Extra Options NEARESTCENTER: The image that is the most central of all the input scenes is the first image processed. Subsequent images are processed, in turn, based on which has its center closest to the center of the first image. NONE: the source images are not resorted; they are processed in the order provided. ly defines additional options for the sorting method. For the current GXL implementation, extra options are specific to the NEARESTCENTER sorting method only. For NEARESTSCENTER, extra options parameters are: <starting_image>: if specified in the extra options field, this image will be the first one added to the mosaic. Once added, the algorithm automatically determines the next image to add by identifying the images that have their center closest to the starting_image, then adding them to the mosaic. Normalization Method Default ly specifies the normalization to be performed to each source image before color balancing computation, cutline generation, or mosaicking. Available normalization methods are: None: does not apply any normalization methods to the input images Hot Spot: removes any hot spots from the input images. 4 GXL-Satellite Mosaic Preparation

11 Preparing images for mosaicking Workflow Parameter Normalization Method Extra Options Color Balancing Method Color Balancing Extra Options Mandatory / Description Adaptive: balanced brightness and contrast using a moving window Order: Corrects the gradual change in brightness from one side to the other (recommended primarily for ScanSAR imagery) ly specifies additional normalization options. For the current GXL implementation, the extra options are available for the Adaptive Filter and Order normalization methods. For Adaptive Normalization: <image_percent>: Specifies the percentage value for the filter size. If no value is provided, a default value of 20% is used. For Order Normalization: <power>: Specifies the degree of the polynomial equation used to normalize the imagery. The power value can be 1, 2, or 3. If no value is specified, a default value of 1 is used. ly specifies the color balancing method to be applied to the final mosaic. Available color balancing methods are: None: (default) images are added to the mosaic without changing the greylevel value. Overlap: performs a least-squares analysis in the overlap areas between images in the mosaic. LUT: uses stored Look-Up Table segments from the source images to control the color balancing. Histogram: sequentially matches the input image histograms to the target mosaic image. Reference: matches the histogram of the source image with the reference image. Neighborhood: Determines a set of color balancing coefficients that change each image pixel based on the pixels values of the intersecting (neighboring) images, regardless of z-order. Specifies additional color balancing options that are dependent on the Color Balancing Method. GXL-Satellite Mosaic Preparation 5

12 Preparing images for mosaicking Workflow Parameter Local Color Balance Mask Mandatory / Description ly specifies whether to apply a local mask to exclude specified pixels from any color balancing computation. Available options are: NONE: no pixels are excluded from the color balancing computation; this is the default value. BIT: used when there are bitmap segments in at least some of the source image files that define exclusion regions. VEC: used when there are polygon vector segments in at least some of the source image files that define exclusion regions. Global Color Balance Mask File Global Color Balance Mask Layer ly specifies a file that, in conjunction with the Global Color Balance Mask layer that identifies regions in the source images to omit from any color balancing computation. Identifies the vector or bitmap segement that contains the color balance mask Cutline Method ly specifies the method to use to compute cutlines for the mosaic. Available options are: Minimum Squared Difference: Determines a cutline in each overlapped area with a minimum squared difference in their gray values at the same location. Minimum Difference: Determines a cutline in each overlapped area between two adjacent images with a minimum difference in their grey values at the same location. Minimum Relative Difference: This approach is similar to Minimum Difference but provides better output in cases where similar sections of data appear dissimilar in different images. EDGE: This method provides better output in urban area mosaicking, or in images containing many linear features. The objective of the EDGE method is to avoid placing cutlines across linear features. 6 GXL-Satellite Mosaic Preparation

13 Preparing images for mosaicking Workflow Parameter Cutline Method Extra Options Mandatory / Description Maximum Data: Specifies that cutlines will be on the boundary of the real image pixels, meaning that NoData pixels will be ignored when the image boundary is determined. IMPORT: This method provides the exact same polygons set by the user as the cutline(s) for the image(s). File Extents: This method specifies that the cutline will be the extents of the input images and will not exclude NoData pixels from the cutline generation process. Specifies additional options for the specified Cutline Method. Options used for all cutline methods except for the File Extents method. Cutline Avoidance Masks Specifies the layer(s) that contains cloud, haze, or shade polygons to be used as masks when generating the output mosaic. The cutline does not include features found under the mask(s) Overwrite Results Specifies whether or not results already existing in the output directory should be overwritten. Table 1: GXL Master Pansharpening parameters Define the following parameters for the Thaichote sensor: a. Enter the Input Scenes: \California\Output\Ortho b. Enter the Output XML File:.\California\Output\Mosaic\Mosprep\Cal.xml c. Set the color Balancing Method to: Bundle d. Set the Cutline Method to: Minimum Squared Difference e. Remove the checkmark from the Auto Constrain Thiessen checkbox. f. Click Submit Job. The GXL Mosaic Preparation module begins to search the scene directory for the images to add to the mosaic. The module computes color balancing coefficients and cutlines for each scene. Pixels containing bad data (clouds, haze, shadows, etc.) identified in the Local Cloud Cover Polygons Layer parameter are automatically removed from the image mosaic. The output is stored as an output XML file, along with auxiliary information. Only a master job is created, as the GXL Mosaic Preparation module is not a distributed process. GXL-Satellite Mosaic Preparation 7

14 Preparing images for mosaicking Results After successful execution, the GXL Mosaic Preparation module generates an output XML file and a series of auxiliary output files and directories. Output from the module includes: Output XML file: this is the key output from the GXL Mosaic Preparation module, and is required as input to the GXL Master Mosaic Generation module. The XML file stores information about the images added to the mosaic, the order in which they are added, and other information and parameters related to the mosaic. Cutlines sub-directory: contains a cutline (in PCIDSK format) for each image comprising the image mosaic Lowres sub-directory: contains a low-resolution preview of the image mosaic. You can load this image in the PCI Geomatics Mosaic Tool to view and edit the mosaic before generating the final image. You can also use this image as a color-balancing reference image when running the GXL Mosaic Update Preparation module. Masks sub-directory: contains a PCIDSK file for each image in the mosaic that contains a mask. Masks are used during the color balancing and mosaic generation processes. You can now use the PCI Geomatics Mosaic Tool to view the mosaic preview and modify the mosaic, or proceed to section. 8 GXL-Satellite Mosaic Preparation