InSAR On Demand!
Ordering Sentinel-1 InSAR datasets from the Alaska Satellite Facility
Content updated 27 September 2022
Synthetic Aperture Radar
Synthetic Aperture Radar (SAR) has the advantage of being able to image the surface of the Earth at any time, regardless of cloud cover. The Sentinel-1 satellite constellation collects SAR data globally, with the potential to collect repeat data as often as every six days, making it a very powerful dataset for time series analysis, change detection, and flood extent mapping.
The phase component of the SAR dataset allows for the detection of very small changes in elevation on the earth's surface from one acquisition to the next. This makes SAR an excellent tool for monitoring deformation caused by earthquakes, volcanoes, ground water subsidence, and other geologic and anthropogenic processes.
SAR Interferometry (InSAR)
By differencing phase images collected from the same location in space at two different points in time, users can generate an interferogram that indicates the location and magnitude of surface deformation that has occurred during the time interval between acquisitions. This approach is called interferometric SAR, or InSAR.
To generate interferograms, specialized software and workflows are used to process Sentinel-1 SLC datasets. The learning curve for the processing workflow is steep, and processing InSAR also requires significant computing power. It can take many hours to generate one interferogram on a desktop computer.
On Demand Processing
The Alaska Satellite Facility (ASF) offers On-Demand Processing of Sentinel-1 products. This allows you to search for Sentinel-1 scene pairs and submit them for InSAR processing directly in the Vertex Data Search interface. ASF uses cloud computing to efficiently process the data, and InSAR products are generally available for download about an hour after they are submitted for processing.
Credit System
On Demand users are given an allotment of 10,000 credits per month to use for processing jobs, and each type of On Demand job costs a different number of credits, as shown in the Credit Cost Table .
When selecting processing options for output products, Vertex displays the number of credits required for each of the different options. Currently the only InSAR option that impacts credit use is the number of looks, which determines the pixel spacing of the output product.
More information about the credit system is available here . If you have any questions or comments, contact ASF at uso@asf.alaska.edu.
Burst-Based InSAR
For users working with smaller areas of interest, ASF now also offers Burst-Based InSAR On Demand processing. Users can search for and submit individual Sentinel-1 bursts for InSAR processing, rather than using an entire Sentinel-1 SLC scene.
Ordering InSAR On-Demand Products using Vertex
The Baseline tool is most appropriate for selecting specific individual pairs to use for interferometry. This is often useful when generating an interferogram for a discrete event, such as an earthquake. Once you find a good acquisition to use as the reference scene, use the Baseline tool to find appropriate secondary scenes.
The SBAS tool is designed to compile a series of many InSAR pairs that covers a long period of time. This time series approach is often used when monitoring long-term processes such as groundwater subsidence or magma chamber dynamics.
In both cases, you will start with a Geographic Search in Vertex to find a reference scene that you want to use for InSAR. You can then select the Baseline tool to find another scene to pair with it to generate a single interferogram, or the SBAS tool to compile a time series of InSAR pairs that cover the same footprint as the reference scene.
Geographic Search
Scroll through the tutorial below to learn how to find Sentinel-1 scenes in ASF's Vertex Data Search portal
Use the navigation bar at the top of the screen to access the Baseline or SBAS tutorials directly if you're already familiar with the Vertex search interface
Data Search - Vertex
Visit ASF's Data Search - Vertex portal to find Sentinel-1 scenes of interest.
On-Demand processing is currently only available for the Sentinel-1 dataset.
Sign in to Earthdata
Sign in using your Earthdata Login credentials.
If you don't already have credentials, click the Register button to sign up for a free Earthdata account .
Draw Area of Interest
Draw an Area of Interest with your mouse using the Area of Interest and Selection Shape tools in the toolbar.
You can draw a box (default), an irregularly shaped polygon, a line, or a single point.
Alternatively...
Import Area of Interest
Alternatively, expand the Area of Interest section. Click the Import File button, or Drag and Drop a file, to import a shapefile, GeoJSON, or KML file.
Note that a shapefile consists of multiple constituent files with the same base name but different file extensions.
If the shapefile is unprojected (in geographic lat/long coordinates rather than projected coordinates), you can just upload the single file with the .shp extension.
If the shapefile is projected, you will need to zip all the constituent files of the shapefile, and upload the zip file instead.
You can also paste well-known text describing the feature into the WKT field.
Well-Known Text (WKT)
Once you've drawn or uploaded an area of interest, the WKT describing the AOI is displayed and can be copied for future reference.
Set Additional Filters
You can narrow your search results by adding Search Filters including a date range, file type, and other parameters.
The additional filters available are specific to the dataset used for the search.
The SLC file type is required for Sentinel-1 InSAR processing. At this time, only the IW beam mode is accepted for On-Demand InSAR processing.
OPTIONAL: InSAR Filters
Restricting the file type to Single Look Complex (SLC) and the beam mode to IW will reduce the number of search returns, and help ensure that only scenes valid for On-Demand InSAR processing are selected.
There are, however, no browse images generated for SLC products. If you want to see browse images for your search results, you will also need to include the GRD file types in your search, even though you will not be able to submit GRD files for InSAR processing.
View Search Results
The search results are listed in the left panel. If you click on a result in the list, the footprint of the image will be highlighted in red in the map. The scene details are listed in the center panel, and all associated files will be displayed in the right panel.
You can also click on a footprint of interest in the map to highlight one of the acquisitions with that footprint in the results list.
In this example, the search was restricted to SLCs, so only the SLC for the acquisition is listed in the right panel.
OPTIONAL: More Like This
If you find a scene with a footprint that covers your area of interest well, click the More Like This button at the bottom of the Scene Detail section for that scene.
This button applies an additional filter to the search, so only acquisitions with the same path and frame as the reference image are displayed in the search results.
OPTIONAL: Browse Images
If the search results include GRDs or other files with associated browse images, the browse images can be displayed on the map.
These browse images are not fully georeferenced, but can be useful for visualizing the general extent and content of the image.
OPTIONAL: Browse Image Settings
Use the toolbar to adjust the appearance of the browse images.
If more than one browse image is associated with the file, use the Product Browse arrows to scroll through the options. Use the Browse Opacity slider to adjust the transparency of the image in the map.
OPTIONAL: Browse Image Viewer
To take a closer look at a browse image, scroll down in the Scene Detail section (center panel) for the selected scene.
Use the icons in the top left corner of the image display to open the browse image in a larger Image Viewer interface, or to download a copy of the browse image. Note that the downloaded image will not include any geospatial properties.
Baseline Tool
Once you've selected a reference scene using the Geographic Search in Vertex, you'll need a secondary scene to match with it to generate an interferogram. The scenes must be acquired fairly close together in space in order for the phase measurements to be coherent enough for interferometry.
The perpendicular baseline indicates the distance between the imaging platform locations during the two acquisitions. The phase difference measurements will be better if the scenes are acquired from very similar locations in space. The Baseline tool finds and lists other acquisitions that are within a suitable range of perpendicular baseline values, allowing them to be paired with the reference scene for InSAR processing.
Scroll through the tutorial below to learn how to use the Baseline tool to pick InSAR pairs for processing
Select Reference Scene
Use a Geographic Search in Vertex to find a suitable reference image. Consider the acquisition date and the scene extent when choosing a reference scene.
Click on the desired scene in the search results (left panel) to display the Scene Detail (center panel) for that acquisition.
Launch the Baseline Search
Click the Baseline button in the center panel for the selected reference image. This will launch the Baseline Search .
The Baseline search is best when you want to pick specific pairs. To generate a time series of interferograms, refer to the SBAS Tool tutorial.
OPTIONAL: Direct Baseline Search
If you know the file name of your reference scene, you can skip the Geographic Search and simply select Baseline from the Search Type menu.
Type or paste the name of the SLC in the Reference Scene field, then click the search button.
Baseline Display
The Baseline tool displays all acquisitions that are potentially suitable for pairing with the reference scene to generate an interferogram.
The name of the Reference Scene is displayed at the top of the page, and is indicated in the plot by a black dot at the (0, 0) position.
Each of the potential secondary scenes is represented by a grey dot in the plot. This indicates how far from the reference scene each acquisition is in space ( Perpendicular baseline on the y-axis) and time (Temporal baseline on the x-axis).
Click on a dot in the plot to display the scene in the results list (left panel), or click a scene in the results list to highlight the corresponding dot in the plot.
Drag the boundary bar to expand the area available to display the plot and results list.
OPTIONAL: Refine Baseline Results
If desired, click the Baseline Criteria button to set a date range, or adjust baseline tolerances.
Baseline Criteria
When you set start and/or end dates, or set the sliders to adjust the Perpendicular or Temporal baseline tolerances, the search results are updated in both the results list and the plot.
Perpendicular Baseline : Perpendicular distance between sensor locations during acquisitions (in meters)
Temporal Baseline: Time between acquisitions (in days)
Select a Scene Pair
Click on an item in the results list to learn more about the scene.
The perpendicular and temporal baseline differences relative to the reference scene are displayed in the results list for reference.
Click on the Scene Detail tab for additional information about the scene.
The reference scene is also listed in the results, with baseline differences of 0 listed for both the perpendicular and temporal baselines.
Add Pair to On Demand Queue
To add an InSAR pair to your On Demand Queue, click the On Demand icon next to the scene you would like to pair with the reference scene.
Select InSAR GAMMA > Add 1 SLC pair.
OPTIONAL: Add All Results
If you want to queue up pairs for all of the scenes listed in the results, there is a bulk On Demand icon at the top of the list.
This will add a set of pairs to the queue, each including the reference scene along with one of the other scenes in the list.
If you want the secondary scenes to be paired up with each other as well, it may be easier to use the SBAS tool. The SBAS tool is designed to include all combinations rather than pairing to a specific reference scene.
OPTIONAL: Change the Reference Scene
To create pairs using a different scene in the results list, click on that scene in the results list and select the Scene Detail tab.
Click the Baseline button at the bottom of the left panel to re-launch the Baseline search using this new scene as the reference.
SBAS Tool
Time series analysis of InSAR products is often used to monitor landscape or geophysical processes, determine rates of change, gain insight into the characteristics of deformation, and correct for atmospheric impacts or other noise signals. One common method for time series analysis is the Small BAseline Subset (SBAS) approach.
SBAS uses a series of many interferograms generated from SAR images acquired over an extended time period, with each individual InSAR pair having a relatively short time interval between acquisitions. A range of short baselines are used, allowing for pairs to overlap each other, and for each reference scene to be paired with multiple secondary scenes.
The SBAS Tool in Vertex assists users in compiling a list of pairs suitable for use in SBAS analysis.
Scroll through the tutorial below to learn how to use the SBAS tool to find and submit a time series of InSAR pairs for On Demand processing
Select Reference Scene
As with Baseline, use a Geographic Search in Vertex to find a suitable reference image.
Click on the desired scene in the search results (left panel) to display the Scene Detail (center panel) for that acquisition.
Launch the SBAS Search
Click the SBAS button in the center panel for the selected reference image. This will launch the SBAS Search.
The SBAS search is the best option when you want to generate a time series of interferograms over a specific area. To pick pairs relative to a single reference scene, refer to the Baseline Tool tutorial.
Reference Scene
As with Baseline, the Reference Scene used to launch the SBAS search is displayed at the top of the screen.
If you already know the filename of the SLC you would like to use as the reference for your SBAS search, you can select SBAS from the Search Type dropdown and enter the filename in the Reference Scene field to launch the tool.
SBAS Tool
The SBAS Tool will display a list of all of the InSAR pairs that are suitable for use in Small BAseline Subset (SBAS) time series analysis based on the acquisition location of the reference scene selected.
Drag the boundary beneath the map upwards to expand the SBAS plot and results list, and use the Zoom tools to focus on particular areas in the plot if desired.
Explore SBAS Pairs
Each dot in the plot indicates an acquisition, and lines between the plots indicate InSAR pairs.
Click on a line in the plot to highlight the pair in the results panel on the far left. Similarly, clicking on a pair in the results panel will display the corresponding line in the plot in red.
The individual acquisitions included in the selected pair are displayed in the center panel, with details for each. The footprints for each of the two acquisitions in the selected pair are displayed in red on the map.
SBAS Criteria
Note that for the selected pair in this example, the footprints just barely overlap. This pair would produce an interferogram containing very little, if any, usable data.
The SBAS Criteria filters include options to refine your results list, including an overlap threshold that can help reduce the number of low-overlap pairs in your time series.
Click the SBAS Criteria button to set additional filters.
Set Overlap Threshold
Select the 50% Overlap Threshold option under the Latitudinal Overlap section of the SBAS Criteria window to restrict the search to include only pairs that overlap each other by at least half of each constituent image.
In this SBAS search example, applying this option reduces the results list to nearly half the number of pairs originally listed. If you have sufficient redundancy in pairs after applying this filter, the overlap threshold setting can be a quick and easy way to remove low-value pairs from your time series.
In some situations, there may be pairs with less than 50% overlap that do cover your area of interest and would be useful in a time series analysis. If the overlap threshold setting is too restrictive, you may need to click through each pair in your results list and look at the footprints in the map to determine which individual pairs to submit for processing.
Constrain Date Range
The SBAS Criteria filters also allow you to apply Date Filters for your time series.
- The results list will be restricted to those pairs that fall within your specified date range.
- The plot will still display dots for all available acquisitions, but will only display lines for the pairs listed in the filtered results.
Adjust Baseline Tolerances
Use the sliders next to the Perpendicular Baseline and Date (temporal baseline) axes to restrict baselines as desired.
Perpendicular Baseline : Perpendicular distance between sensor locations during acquisitions (in meters)
Date (Temporal Baseline): Time between acquisitions (in days)
OPTIONAL: Seasonal Search
The SBAS Criteria filters also support seasonal searches. Click the Seasonal Search toggle switch and use the sliders in the Season Filters section to set a start and end date for your season of interest. This will restrict the results list to only those pairs that fall within that range of dates in any given year.
- Setting both a Date Filter and a Season Filter will constrain the seasonal search to the overall date range.
- Leaving the Date Filter fields empty when applying a seasonal search will return seasonal results for all available years.
A seasonal search can be particularly useful in regions exhibiting strong seasonality, where comparisons across seasons may not be valid, or the impacts of seasonality can obscure fundamental changes over time.
OPTIONAL: Custom Pairs
There may be times when you want to add a pair to your time series that's not automatically included in your results list.
The Custom Pair toolbar allows you to select two acquisitions that have not already been paired and add the pair to the results list.
This feature is particularly useful for bridging gaps in seasonal searches, or adding more redundancy in areas that have sparse coverage under the baseline or overlap tolerances you've applied.
To walk through the workflow for generating a custom pair, see the slideshow below.
Demo: Add Custom Pair
Click the arrows or swipe to move through the slideshow, which demonstrates the steps involved in working with Custom Pairs
01 / 05
Add Time Series to On Demand Queue
Once you've adjusted your results list so that it includes only the pairs you want to use, you can submit the entire list for On-Demand processing.
Click the On Demand icon at the top of the list, and select the InSAR GAMMA option to add all of the SLC pairs in the time series to the On Demand Queue.
Keep in mind that there is a credit system in place for ordering On Demand products. Each user has 10,000 credits to use for On Demand processing per month, and different job types use different numbers of credits. If your list requires more credits than what you have available, you may need to submit it in batches over subsequent months.
More information on the credit system, including a Credit Cost Table is available here .
Contact ASF at uso@asf.alaska.edu if the credit limit is not sufficient for your project.
OPTIONAL: Add Individual Pairs to On Demand Queue
You can also add individual pairs to the On Demand Queue for processing, rather than submitting the entire list.
Scroll through the results list, and use the On Demand icon next to specific pairs to submit them to the queue.
OPTIONAL: Download CSV File of Results List
Click the Pairs download icon to download a CSV file listing all the pairs in your results list.
This is a very useful feature if you want to use the tool to identify pairs, but plan to process the interferograms yourself.
Submit and Download On-Demand Jobs
Open On Demand Queue
Once you've finished queuing InSAR jobs, click the large On Demand icon and select On Demand Queue from the list of options.
This will open the On Demand Queue window, where you can review your pairs, select processing options, and submit the pairs for processing.
Set InSAR Options
Adjust the Processing Options for the InSAR jobs in the queue. Descriptive tool tips are available; hover over each processing option in Vertex to learn more.
Options: Water Masking
Applying the Water Mask option prevents phase unwrapping over large coastal and inland waterbodies. Water can sometimes exhibit coherence values that allow it to be included in phase unwrapping, which can introduce erroneous deformation signals or phase jumps over land.
ASF's InSAR Water Masking tutorial demonstrates the impact that water masking can have on your phase unwrapping results, and illustrates the change that we made to our water masking approach in September 2022.
Scroll down past the image, or click the button in the top right corner (or the link card below) to launch the tutorial in a separate window.
Options: MintPy
If you are planning to use MintPy software to run SBAS analysis on your output interferogram time series, click the Set MintPy Options button to include the optional products that are required for the MintPy workflow.
This will select the DEM, Look Vectors, and Wrapped Phase (GeoTIFF) for inclusion in the output product package.
Other optional outputs can also be selected in addition to these minimum requirements, but using this button will ensure you have the ancillary files you need for MintPy analysis.
Submit Jobs
You can sort the jobs in your queue, and remove individual jobs you do not want to submit for processing. You can close the queue if you want to add more jobs before submitting; the current contents will remain in the queue.
Once you're ready to submit the jobs for processing, click the Submit Jobs button.
Add Project Name
You have the option to add a Project Name to the batch of jobs you are submitting. This can make it easier to manage your finished products.
You can type in a new name, or select from a list of project names you've used in the past.
Click in the field to display a menu of previously used names. Scroll down to select the desired project name, or start typing to filter the list.
Click the Submit Jobs button to complete the submission process.
Submission Confirmation
Once you submit your jobs, a confirmation message is displayed.
Click on the message to open the On Demand Search, where you can explore and download your On Demand products.
On Demand Search
You can always access your previously submitted On Demand products in the On Demand Search.
To launch this search interface, either select On Demand Products from the Search Type menu, or click the large On Demand icon and select Submitted Products.
Pending Products
Jobs that have been recently submitted will be displayed with a Pending status label. This will change to Running once the jobs are actively being processed.
On Demand Search Filters
You can filter your On Demand products based on the Project Name. Use the drop-down menu in the Project Name field, or start typing to restrict the list.
There are also additional Filters that can be applied to your On Demand search results:
- Date Filters to set a range of dates for source scene acquisition
- Job Status to select Pending, Running, Succeeded or Failed jobs
- Product/Source Scene to search for specific text contained in the product or source scene name.
Completed Products
Once a job is complete, the status label is removed. The filename changes from the source reference scene name to the filename of the finished product package, which has a .zip extension.
Products are available for download for 14 days after processing is complete.
Product Details
Click on a finished product in the left panel to select it. This allows you to:
- View product details in the right panel, including the time remaining until expiry and the processing options that were applied
- Access all download options in the right panel
- View scene details for the two source scenes in the center panel
- Display available browse images on the map or in the image viewer
Use the Product Browse arrows to change the browse image displayed on the map. You can display either the wrapped or unwrapped interferogram.
Use the Browse Opacity slider to change the transparency of the displayed browse image.
Expired Products
Products expire after 14 days. While expired products are no longer available for download, the metadata is retained and remains listed in your On Demand Search results.
You can hide expired products in your search results by clicking the Expired button at the top of the list. Click it again to display expired products.
Resubmitting Expired Jobs
Expired jobs can be resubmitted for processing in two ways:
1. Use the same processing options as the original product
Click the Expired... button next to the product in the left panel, and select Resubmit. You can choose to use a different Project Name, but all other processing parameters will be retained from the original product.
2. Use different processing options than the original product
Click the On Demand icon next to the Expired... label to simply add the source pair to the On Demand Queue. You can then select your desired options, just as you would if the InSAR pairs had been queued from the Baseline or SBAS searches.
Downloading Products
You can download completed products in your browser one at a time by selecting a file in the results list and clicking the download icon in the right panel.
To download multiple products, click the cart icon (either in the results list in the left panel or next to the file information in the right panel) to add a product to the Downloads queue. A message is displayed when products are added to the queue.
Click on the Queue button at the top of your results list to add all of the products listed in the left panel to your Downloads queue.
Download Queue
Click the large Downloads icon to open the Downloads queue.
You can use the icons next to each product to download products individually or remove them from the queue.
To download all the products in the queue using a Python script, click the Data Download button and select Download Python Script. If you have Python installed, you can simply double-click the downloaded .py file. The script will launch, prompt you for Earthdata Login credentials, then start downloading the contents of the queue.
The Copy URLs button copies a list of the download URLs for the products in the queue, which you can use to create your own download script if desired.
InSAR Product Files
The InSAR products are downloaded in zip archives, which include GeoTIFFs of the interferograms, coherence and displacement maps, and a number of ancillary rasters, browse images, and accompanying documentation.
Click on the map below to explore some sample On Demand InSAR output files. This InSAR product captures an earthquake event in Ridgecrest, California in July 2019. The map displays the browse image for the wrapped interferogram and the GeoTIFF of the unwrapped interferogram.
InSAR product processed by ASF DAAC HyP3 2021 using GAMMA software. Contains modified Copernicus Sentinel-1 data 2019, processed by ESA.
If you are new to ASF's On Demand InSAR products, open the README file included in the zip file to find out more information about the files included in the product package. It can be read either as a text file or in a Markdown viewer/editor.
Refer to our Sentinel-1 InSAR Product Guide for additional information on the On Demand InSAR processing workflow and options, files included in the product package, and guidance for usage.
Explore the Data
To learn about the datasets included in the InSAR product package, and to explore techniques for interacting with and interpreting the data, refer to our Exploring Sentinel-1 InSAR Products Story Map .
