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20-43. Fusing Synthetic Aperture Radar and lidar with optical imagery to improve our ability to detect and interpret change on Earth’s surface


Closing Date: January 6, 2022

This Research Opportunity will be filled depending on the availability of funds. All application materials must be submitted through USAJobs by 11:59 pm, US Eastern Standard Time, on the closing date.



Orbital assets now image Earth’s surface at sub-daily to weekly time steps, at ever finer resolution (< 1 m to several 10’s of meters). This massive quantity of data now outpaces our ability to interpret it, with even more data and imagery arriving soon. With this opportunity, U.S. Geological Survey (USGS) seeks applications for a full-time Mendenhall Post-Doctoral Research Fellow who will explore how to assess landscape change from in lidar, synthetic aperture radar (SAR) and optical data. Our intent is to explore how changes in lidar and InSAR (e.g., decorrelation) can be rapidly interpreted for applications including natural hazards, forestry, hydrology, and urban and/or resource development. 

The selected Fellow will be able to access current and upcoming satellite radar, lidar and optical mission data (e.g., NASA-ISRO SAR (NISAR), Capella, Landsat / Sentinel and/or Planet, Maxar) to explore relationships between radar or lidar and optical imagery over time, space and dimension. The Fellow will be based in the National Geospatial Program, with the duty station to be determined, and will work directly with the National Land Imaging (NLI) Program and the Innovation Center. This position will be enabled by access to the variety of imagery, lidar and radar resources available to the USGS and partner Federal Agencies and provide the Fellow with an opportunity to pursue their own scientific interests within the described framework.

The mission of the National Geospatial Program is to provide National topographic information to advance science, support government, enlighten citizens, and enable decision making. The NGP provides a foundation of digital geospatial data representing the topography, natural landscape, and engineered environment of the United States. As part of this mission, the 3D Elevation Program has been partnering to complete acquisition of high-resolution elevation data in the form of Nationwide lidar (IfSAR in Alaska) and is nearing completion of a once-over baseline collection and is beginning to look to the future. The 3D National Topographic Model is combining information from the 3D Elevation Program with the National Hydrography Program to update and improve the mapping of the hydrography across the nation. Knowing where areas have changed significantly enough to warrant updated mapping is key to the Program’s success. Targeting and prioritizing areas for recollection will likely be focused on a change-based model using a tipping and queuing approach, where once a certain area as undergone enough change, it would be targeted for higher-resolution type acquisitions. This not only applies to structural change, but hydrologic changes as well. What technologies could be used and what defines ‘enough’ change are important research questions the NGP would like the selected Fellow to attempt to answer. Imagery, both global optical and radar, managed by the National Land Imaging (NLI) Program are ideal source data streams to accomplish this detection task.

A fundamental goal of the NLI Program is to provide the Federal Government and the public with a primary source of high-quality, well-calibrated remotely sensed data to measure Earth’s surface. NLI Program mission objectives also include evaluating new Earth observation technologies and systems toward science research and operational use goals, improving understanding of national and international remote sensing user needs, and developing new Earth science remote sensing capabilities, data algorithms, tools, and techniques. The NLI ensures the continuous availability of moderate-resolution satellite imagery and other remotely sensed and geospatial data. A key responsibility of the NLI Program is providing worldwide access to data acquired since 1972 by the USGS flag ship Landsat satellite series.  NLI Program contributes nationally and internationally to the advancement of land remote sensing technologies and applications. To complete these goals, the NLI Program relies on partnerships with the National Aeronautics and Space Administration (NASA) and other Federal agencies and continually grows cooperative relationships with industry, foreign space programs, and international consortia. The NLI Program also supports development of national and international policy on Earth observations and land imaging.

The Mendenhall Fellow will work with a team of NGP and NLI scientists to advance the understanding Earth surface change fusing spaceborne and airborne optical, radar, lidar and other relevant data. Experience with Landsat, Sentinel-2, Planet and other high-resolution commercial imagery sources, radar, lidar and airborne data are needed. Potential research topics include:

  • Techniques for extracting Earth surface composition, change and other characteristics from imagery and radar data
  • Interferometric synthetic aperture radar (InSAR) applications for above-ground or hydrologic features, especially backscatter and InSAR uses of commercial X-Band satellite systems (e.g., Capella and or ICEYE) for characterizing land cover and vertical motion
  • Discriminating high-frequency processes (such as seasonal plant responses and hydrologic changes) from abrupt or longer-term trends (such as from climate change)
  • Artificial Intelligence or Machine Learning approaches to identifying changes in optical imagery and/or radar sources in combination
  • Data mining of time series data from Landsat, Sentinel-2, Planet and other data streams
  • Techniques for understanding the uncertainty inherent in both spectral and three-dimensional values from optical, radar and/or lidar systems.
  • Correlating land-use/land-cover changes with land level changes.  Does a change in a particular class of land cover foreshadow subsidence (or vice-versa)?  Are areas undergoing active land level change also undergoing Land Use/Land Cover transition?
  • Quantifying hydrologic system change, for example in snow or ice depth, surface composition, glacial thickness, and/or lake volume and measuring change over time

A successful applicant must show evidence of the following: 

  • Demonstrated record of peer-reviewed publications related to science and applications for 2D or 3D remote sensing and time series changes
  • Demonstrated research record using radar data for understanding 3D structure 
  • Strong computer programming, image and data processing skills
  • Excellent oral (including public speaking) and written communication skills. 
  • Experience building and/or working in collaborative, diverse and inclusive team environments 
  • Strong interpersonal and communication skills 

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.

Proposed Duty Station: Fort Collins, Colorado; Reston, Virginia; or other USGS office in the U.S.

Areas of PhD: Remote sensing and GIS, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet the qualifications for one of the following:  Research Cartographer, Research Computer Scientist, Research Geographer, Research Geologist, or Research Physical Scientist.

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Human Resources Office Contact: Audrey Tsujita, 916-278-9395,