Check Data Compatibility

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Lesson 1 of 1

Check Data Compatibility

In this quick guide, you will:

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Learn the input data requirements for each SAR Essentials tool. * •

Open and display two Umbra Single Look Complex (SLC) images in ENVI. * •

Run the SAR Compatibility Check tool to determine if the Umbra images are suitable for Coherent Change Detection (CCD). * •

Rerun the SAR Compatibility Check tool to determine if the Umbra images can be used with other SAR Essentials tools.

Sample Data

The exercises in this quick guide use two overlapping Umbra SLC images for demonstration. Download the ZIP file below, and extract the contents to a dedicated directory on your computer.

[SAREssentials_CheckDataCompatibility.zip

251.5 MB

DownloadArrow down with horizontal line beneath it](assets/SAREssentials_CheckDataCompatibility.zip)

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File names: Raster files are named Umbra_Wenchang1_slc and Umbra_Wenchang2_slc. Also included are ENVI header files (.hdr) and ENVI SARscape metadata files (.sml). * •

Acquisition dates/times: Both images were acquired on 27 May 2023. One was acquired at 14:14:11 UTC, and the other was acquired at 14:15:48 UTC. * •

Processing notes: The source datasets were Sensor Independent Complex Data (SICD) files in National Transmission Imagery Format (NITF), which require the ENVI NITF/NSIF Module to read. Since not all users have the ENVI NITF/NSIF Module, we used the "Imported data" option in the SAR Basic Data Processing tool to create SLC images that are in SARscape format instead of SICD. * •

Source: Umbra Space(opens in a new tab). The source IDs are 2023-05-27-14-14-11_UMBRA-05_SICD and 2023-05-27-14-15-48_UMBRA-05_SICD.

Background

Each SAR Essentials tool has specific requirements for input data format and viewing geometry. A recommended first step before using any SAR Essentials tool is to check whether your input data meet these requirements. You can use the SAR Compatibility Check tool for this purpose.

If you provide a list of SAR input files, the SAR Compatibility Check tool will test all combinations of the files for acceptable use with tools that require two input files. See the table below for tools that require two files.

Some tools such as SAR Coherent Change Detection have strict requirements for viewing geometries. The SAR Coherent Change Detection help topic lists these requirements. Rather than review image metadata (provided as JSON files) to determine suitability for Coherent Change Detection (CCD), you can run the SAR Compatibility Check tool. The Report panel lists all image properties, geometry requirements, and whether or not the images can be used for CCD. Thus, SAR Compatibility Check is a great tool for reviewing image properties--such as incidence angles, orbital directions, and footprint areas--if you are unfamiliar with your images.

The following table lists the number of files and geometry types that each tool supports. Every tool accepts original SAR data formats (NITF, HDF5, JSON, etc.) in addition to SARscape-imported formats (_slc.sml, pwr.sml, _gr.sml).

SAR Essentials Tool	Required Number of Input Files	Accepted Viewing Geometries
SAR Basic Data Processing	Any	Single Look Complex (SLC) Power images in slant-range or ground-range geometry
SAR Radar Cross Section	1	SLC Power images in slant-range or ground-range geometry
SAR Height Estimation	1	SLC Power images in slant-range or ground-range geometry
SAR 3D Point Height Estimation	2	SLC Power images in slant-range or ground-range geometry
SAR Amplitude Difference	2	SLC Power images in slant-range or ground-range geometry
SAR Amplitude Change Detection	2	SLC Power images in slant-range or ground-range geometry
SAR Coherent Change Detection	2	SLC
SAR Coherent and Amplitude Change Detection	2	SLC
SAR Interferometric DSM	2	SLC
SAR Stereo-Radargrammetry DSM	2	SLC Power images in slant-range or ground-range geometry
SAR Moving Target Detection	1	SLC
SAR Dynamic Moving Target Detection	1	SLC
SAR Velocity Estimation	1	SLC Power images in slant-range or ground-range geometry Geocoded data
SAR Inverse-SAR Refocusing	1	SLC
SAR Ship Detection	1	SLC Power images in slant-range or ground-range geometry Geocoded data

Let's look at an example of using the SAR Compatibility Check tool in a CCD scenario.

Exercise: Check Data Suitability for CCD

In this exercise, you will determine if a pair of Umbra images is suitable for the SAR Coherent Change Detection tool.

Open and Display SLC Images

1

Start ENVI. - 2

Select File > Open from the Menu bar. An Open dialog appears. - 3

Go to the location where you saved the sample data for this quick guide. - 4

Use the Ctrl key on your keyboard to multi-select the files Umbra_Wenchang1_slc and Umbra_Wenchang2_slc. - 5

Click Open. The images are added to the Layer Manager and displayed in the Image window. - 6

Click the Zoom to Full Extent button in the Toolbar to view the full extent of the images.

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Zoom to the launch tower, which is the brightest object in the scene. - 8

In the Layer Manager, uncheck and check the first layer (Umbra_Wenchang2_slc) to compare it with the second layer (Umbra_Wenchang1_slc). The images were acquired one minute apart.

Neither image is georeferenced to a standard map projection, but ENVI applies "pseudo" (approximate) georeferencing to both images so that they geographically line up in the same view. You can see slight differences in acquisition geometry between the images, as objects and shadows shift directions.

Suppose your objective is to monitor subtle changes to the landscape from vehicle or foot movement. Coherent Change Detection (CCD) is ideal for this scenario since the temporal difference between the images is small (one minute) and the images have significant overlap. You can use the SAR Compatibility Check tool to see if they are indeed suitable for CCD.

Run the SAR Compatibility Check Tool

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In the Toolbox, expand the SAR Essentials folder and double-click SAR Compatibility Check. The SAR Compatibility Check dialog appears. - 2

Cick the green Add File(s) button. A file selection dialog appears. - 3

Use the Ctrl key to multi-select Umbra_Wenchang1_slc.sml and Umbra_Wenchang2_slc.sml. - 4

Click Open. The images are added to the Input File List section. - 5

Click the Check type drop-down list and select Coherent Change Detection.

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Click the Next button.

When processing is complete, the Report panel appears. The "Summary" section shows whether or not the individual images and image pairs are suitable for CCD. In this case, the report shows that they are not suitable for use with CCD.

Why are they incompatible? The remainder of the Report panel provides some clues. Watch the following video to learn how to interpret the information in the Result panel.

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This is a modal window.

While the SAR Compatibility Check tool is still open, you can check if the Umbra image pair is suitable for other SAR Essentials tools.

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Click the Back button to return to the first step. - 8

Click the Check type drop-down list and select All Processing. - 9

Click the Next button. After a few seconds, the Report panel appears. - 10

Review the "Summary" section at the top of the report. What SAR Essentials tools show "Compatibile images: (1) (2)"? This means that either Umbra image will work with those tools.

You can scroll down further to review details of the Umbra images and why they are not compatible with some tools.

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Click the Finish button to close the SAR Compatibility Check tool.

This concludes the quick guide.

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