Viewing Results
Two programs have been developed by Scott Shaffer at JPL/Caltech for viewing SAR images, interferograms and other imagery on X Window System displays. There are Perl scripts included with ROI_pac (dgx.pl and mdx.pl) that will automatically run DGX and MDX, respectively, with the proper parameters to display the ROI_pac results.
The older program DGX, which only works on certain older computer systems with 8-bit color displays, is available from Open Channel Foundation
The newer program MDX, which works on modern 24-bit displays with the X Window System (a.k.a X11), is available for licensing from JPL. It probably won't be released to Open Channel Foundation.
The new MDX license procedure is to access http://download.jpl.nasa.gov, select "Request Software" and follow the instructions provided. NOTE: You must be a "professor or higher" permanent to complete a successful application -- students or other "individuals" will not be approved for use of this software. The "designated signatory" needs to be either the head of a department or someone from who can legally bind the organization to the terms of the license. It might take several weeks to months to receive a response from JPL to your application. Once the JPL Software Release office has the signed license forms, they can give a user name and password to download MDX. The MDX license, like ROI_pac, is free for non-commercial purposes.
The old procedure was to send an email to softwarerelease@jpl.nasa.gov . You will have to fill out some forms, the license goes through an approval process, and then a license is sent out for signature.
Another option is to convert the ROI_pac files to "flat" binary files and load them into GMT or other visualization software. A rmg2grd.pl script that converts files to GMT is available on the ContribSoftware page.
Some basic mdx commands:
Intro: MDX is ideal for reading the various ROI_PAC file formats. It automatically reads the extension at the end of the file (*.slc, *.unw, *.dem, *.hgt, *.cor, *.msk, *.int) to figure out the file format, and reads the .rsc file for the information on the number of rows and columns. Remember that many of the files follow the Richard M. Goldstein (rmg) format (real*4: including .unw, .hgt, .msk and .cor): each line has twice the number of columns specified. For each line, first there is a column width of "amplitude" values, then a column's width of "phase" values. The other common types of file formats are integer*2 (.dem) and complex*8 (.slc and .int)
Basic features: For all files except .dems there should be two buttons in the lower left: an "amplitude" button and a "phase" button. If you left click on one or the other it should show that component of the file you are looking at. If you'd like to see both phase and amplitude simultaneously, left click on one of the buttons then center click on the other.
If you left click on a given pixel, the COL (column) and ROW value of that pixel will appear immediately above the image as well as the amplitude and phase values of that pixel.
If you'd like to change the stretch on the amplitude or the wrap rate on the phase right click on the "amplitude" or "phase" buttons, and then use the scroll down menus and type in the values that you'd like. For example, we often need to change the wrap rate to 6.28 radians. To do this we right click on "phase", find "WRAP" in the scroll menu then type "6.28" next to the word "Wrap:" Sometimes the amplitude image might appear washed out. It sometimes helps to right click on "amplitude" and select SDEV from the pull down menu. You can also use the "right click" menu to change the color table on the last line of the pop-up window. Common choices are cmy and grey.
Most of the pop-up window settings can be specified from the command line when you summon mdx. To get a full list of the options, just type mdx. For example, I often type mdx.pl filename -le (or -be) to view a file that is little endian or big endian.
There are a series of menus across the top of the viewer that will allow you to zoom in and zoom out, print to a file or perform other commands. You can also execute these commands with key strokes as long as you type the key strokes while the cursor is over the active image area.
Known issues: If you want to view a file with more than 30,000 lines you will first have to zoom out and then zoom in to your region of interest.
There is currently no functionality to flip an image left to right like there was in the old DGX. This was useful for descending images which look backwards (if we consider north to be up in the image).