roipac:overview

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--- roipac:overview [2007/05/07 18:09]
rdubuc
+++ roipac:overview [2010/09/22 20:47] (current)
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 ===== Obtaining SAR data =====
-Next it is time to actually download your different scenes. You will likely
+Next, it is time to actually download your SAR data. You will likely
-need to produce many interferograms in order to fully investigate an area, and for each interferogram you will need two SAR scenes. The program [[EOLISA]] is a great tool that pairs scenes that can
+need to produce many interferograms in order to fully investigate an area, and for each interferogram you will need two SAR scenes.
-be correlated. It allows you to search for various pairs based on their location, date, baseline
+There are various [[sar|online catalogues]] where you can search for interferometric
-(the perpendicular distance between the 2 passes) and other various parameters. You can purchase scene
+pairs based on the location, date, and baseline.  If your institution is a
-data directly through EOLISA, or if your institution is a member of the WInSAR Consortium you can
+member of the
-download data for the western U.S. free of charge from the [[http://winsar.unavco.org|Winsar website]]. Links to detailed explanations: [[EOLISA|EOLISA]]; [[winsar|WInSAR]].
+[[sar#WInSAR|WInSAR Consortium]], you can
+download SAR data for the western U.S. from their website.
+===== Downloading Orbit Files =====
+There exist two sources for obtaining accurate orbits for the ERS satellites. The [[http://www.deos.tudelft.nl/|Delft
+Institute for Space-Oriented Space Research]] (DEOS) provides orbit
+information for both [[http://www.deos.tudelft.nl/ers/precorbs/|ERS and
+ENVISAT]]. An alternative source is the
+[[http://earth1.esrin.esa.it/f/eeo2.400/pgersorbprc|Precise Orbit Product]]
+through the [[http://www.esa.int/|European Space Agency]] (ESA).  Download
+instructions are posted [[orbits|here]].  This step does not have to be repeated once the orbit files are downloaded for a given scene.
 ===== DEM Preparation =====
-In order to use the two pass method, a Digital Elevation Model (DEM) is
+In order to use the two-pass method, a Digital Elevation Model (DEM) is
 necessary to subtract out the topographic contribution from the
 interferogram. Global DEM data can be obtained from the [[http://srtm.usgs.gov/|Shuttle Radar Topography Mission (SRTM)]].
-It can also be obtained directly from SAR scenes. A detailed list of procedures that explain
+It can also be obtained indirectly from the SAR scenes using the three-pass
-how to use an SRTM DEM can be found here: [[srtm|Using SRTM data]]. Details on how to use SAR
+method. A detailed list of procedures that explain
-data can be found here: [[sar_dem|Using SAR data]].
+how to use SRTM data can be found here: [[srtm|Using SRTM data]]. This step does not have to be repeated once the DEM is created.
 ===== ROI_PAC Processing =====
 You are finally ready to use the program ROI_PAC to produce interferograms.
-You will need to be familiar with Unix commands in order to store data and perform tasks.
+You will need to be familiar with [[:links#Unix|Unix commands]] in order to
+navigate through the file system and perform tasks.
-  - After you have downloaded your scene data,
+**1)** After you have downloaded your SAR data and
-you will have to pre-process that data using the [[:roipac:process:makeraw|]] script.
+[[:roipac:process:process#File Management|renamed]] the files
-  - You will then need to create a [[:roipac:process:parameter|parameter file]] that tells ROI_PAC where to obtain the input
+appropriately, you will have to pre-process
-files, the processing parameters, and where to put the output files.
+ that data using the [[:roipac:process:process#make_raw.pl|make_raw.pl]] script.
-  - Finally, in order to process the data you will need to run the script called
-[[:roipac:process:process2pass|process_2pass]].
+**2)** Create a [[:roipac:process:process#Parameter File Setup|parameter file]] that tells ROI_PAC
-''**process_2pass.pl**'' is the primary processing script that will run a long series of programs
+the location of the SAR data
+files, the various processing parameters, and where to place the output files.
+**3)** Finally, start the processing by running the script
+[[:roipac:process:process#process_2pass.pl|process_2pass.pl]].
+This perl script runs a sequence of programs
 that eventually produces your differential interferogram.
-  - Since this process involves many complicated steps, be prepared to encounter various types of
-problems. While you run process_2pass, **Log** files will be produced in the directory in which
-your data is stored. These files record what the program has done and are
-useful for [[:trouble|troubleshooting]] when something goes wrong.
 ===== Viewing Your Results =====
@@ Line 57: / Line 73: @@
 It's now time to interpret your data! ROI_PAC produces a long list of
 intermediate and final [[:output|output files]].  Typically, the final product
-is a geocoded unwrapped interferogram (geo_//date1-date2//.unw).  You can
+is a geocoded unwrapped interferogram (geo_//date1-date2//.unw).  An image
+viewer is not distributed along with
+ROI_PAC.  You can
 use a variety of external programs to view your results (i.e. mdx, dgx,
-Matlab, GMT, ENVI, or other program that is flexible enough to read a binary
+[[:matlab|Matlab]], GMT, ENVI, or other program that is flexible enough to read a binary
-image file).  Note that an image viewer is not distributed along with
+image file).
-ROI_PAC.   After you view your results, you may choose to re-process your data
+After you view your results, you may choose to re-process your data
 with different initial [[:roipac:process:parameter|parameters]] or experiment with
 some [[:advanced|advanced techniques]].