Remote Sensing Data Access – A review of online resources for hyperspectral imagery

Hyperspectral CubeIn our previous post – Remote Sensing Data Archives – we explored some of the many general online data discovery tools for obtaining remote sensing imagery. We now sharpen our focus to the field of hyperspectral remote sensing, aka imaging spectrometry, and delve into resources for accessing this particularly versatile type of imagery.

Hyperspectral imaging emerged on the remote sensing scene in the 1980s, originating at the Jet Propulsion Laboratory (JPL) with the development and deployment of the Airborne Imaging Spectrometer (AIS), followed soon thereafter by the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). Since then hyperspectral imaging has evolved into a robust remote sensing discipline, with satellite and airborne sensors contributing to numerous applications in Earth observation, and other similarly sophisticated sensors being used for missions to the moon and Mars.

The premise behind hyperspectral imaging is that these sensors measure numerous, relatively narrow, contiguous portions of the electromagnetic spectrum, thereby providing detailed spectral information on how electromagnetic energy is reflected (or emitted) from a surface. To give this some perspective and provide an example, this can equate to measuring the visible portion of the spectrum using 50 or more narrow bands as opposed to three broad bands (i.e., red, green and blue) that we typically see with cameras and our eyes. Because objects (plants, soil, water, buildings, roads, etc…) reflect light differently as a function of their composition and structure, this enhanced spectral resolution offers more information with which to identify and map features on the Earth’s surface.

For those interested in hyperspectral remote sensing, and curious to see what can be achieved using this type of data, let’s look at some of the archives that are available:

  • Hyperion – The Hyperion sensor (220 bands; 400-2500nm; 30m resolution) is located on NASA’s EO-1 satellite, and although deployed in 2000 as part of a one-year demonstration mission, the satellite and its onboard sensors have shown remarkable stamina, continuing to collect data today. Archive data from Hyperion are available through both Earth Explorer and GloVis, and new data can be requested through an online Data Acquisition Request (DAR).
  • HICO – The Hyperspectral Imager for Coastal Ocean sensor (128 bands; 350-1080nm; 90m resolution) was installed on the International Space Station (ISS) in 2009 and is uniquely configured for the acquisition of ‘dark’ targets, specifically coastal aquatic areas. The sensor was initially developed and sponsored by the Office of Naval Research, with continuing support now provided through NASA’s ISS Program. Archive data from HICO, as well as requests for new data, are available through the HICO website hosted by Oregon State University; however, interested users must first submit a short proposal to become part of the HICO user community.
  • CHRIS – The Compact High Resolution Imaging Spectrometer (18-62 bands; 410-1020nm; 17-34m resolution) is the main payload on ESA’s Proba-1 satellite, which was launched in 2001. As with the EO-1 satellite, Proba-1 was only intended to serve as a short-lived technology demonstrator, but has managed to continue collecting valuable science data for more than a decade. Data from CHRIS are available to registered users, obtained via submittal and acceptance of a project proposal, through ESA’s Third Party Missions portfolio on Earthnet Online.
  • AVIRIS – The Airborne Visible Infrared Imaging Spectrometer (224 bands; 400-2500nm, 4-20m resolution) has been supporting hyperspectral projects for more than two decades, and can be credited as a true pioneer in the field. AVIRIS is most commonly flown onboard a Twin Otter turboprop or ER-2 jet, but has also been configured to operate from several other airborne platforms. Images from 2006-2011 are available through the AVIRIS Flight Data Locator, with plans to soon expand this archive to include additional imagery from 1992-2005 (currently available through request from JPL).
  • NEON – The National Ecological Observatory Network is a continental-scale network of 60 observation sites located across the United States, where a standardized set of field and airborne data are being collected to support ecological research. Remote sensing data are being acquired via the Airborne Observation Platform, which includes a high-resolution digital camera, waveform LiDAR, and imaging spectrometer. The NEON project is adapting an open data policy, but data acquisition and distribution tools are currently still in development. Thus, initial “prototype” data, which includes a sampling of hyperspectral imagery, are being made available through the NEON Prototype Data Sharing (PDS) system.
  • TERN – The Terrestrial Ecosystem Research Network is an Australian equivalent of NEON, providing a distributed network of observation facilities, datasets, map products and analysis tools to support Australian ecosystem science. Within this larger project is the AusCover facility, which leads the remote sensing image acquisition and field validation efforts for TERN. Current hyperspectral datasets available through AusCover include both airborne data and a comprehensive collection of Hyperion imagery. Data are accessible through the TERN Data Discovery Portal and the AusCover Visualization Portal.

These aren’t the only hyperspectral instruments in operation. There are new instruments, such as the Next Generation AVIRIS (AVIRIS-NG), Hyperspectral Thermal Emission Spectrometer (HyTES) and Portable Remote Imaging Spectrometer (PRISM), which all recently conducted their first science missions in 2012. There are a growing number of hyperspectral programs and instruments operated by government agencies and universities, such as the NASA Ames Research Center and the Carnegie Airborne Observatory (CAO). There are various airborne sensors operated or produced by commercial organizations, such as the Galileo Group, SpecTIR, HyVista and ITRES. And there are also a number of new satellite-based sensors on the horizon, including HyspIRI (NASA), EnMAP (Germany), PRISMA (Italy) and HISUI (Japan).

It’s an exciting field, with substantial growth in both sensor technology and analysis methods continuing to emerge. As the data becomes more and more available, so too does the potential for more researchers to get involved and new applications to be developed.

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Remote Sensing Data Archives – Getting your hands on all that imagery

Remote Sensing DataThere are now vast collections of remote sensing imagery available, much of it readily available for you to download, but it’s not always obvious where and how to access these archives. Below we explore some of the many publically available resources where users can search for and download remote sensing data for their own projects.

As you would expect, government agencies support some of the largest remote sensing data resources, most notably NASA in the U.S. and the ESA in Europe. These agencies provide robust web-clients that can be easily used to discover and download extensive collections of Earth observing data:

  • For NASA, the centralized go-to data repository can be found on the Earthdata website, which itself provides an integrated portal for accessing a wealth of information related to NASA’s Earth Observing System Data and Information System (EOSDIS). Within the Earthdata website you will find links to Reverb, the “Next Generation Earth Science Discovery Tool”, which allows users to search and explore more than 3200 different datasets distributed throughout NASA’s 12 EOSDIS Data Centers.
  • For the ESA, which represents an international consortium of more than 20 European Member States, Earth observing data is primarily hosted through Earthnet Online. This website offers users access to data from the full collection of different ESA Earth Observing Missions, Third Party Missions, ESA Campaigns, and GMES Space Component data.

For other entry points to U.S. data archives, you can also visit the USGS Global Visualization Viewer (GloVis) or USGS EarthExplorer (EarthExplorer) to access data from particular sets of sensors. Alternatively, one can directly visit the various EOSDIS Data Centers, which each provide their own unique data discovery tools, such as the NSDIC Data Search tool at the National Snow & Ice Data Center (NSDIC) Distributed Active Archive Center (DAAC) and the Mercury tool at the Oak Ridge National Laboratory (ORNL) DAAC for Biogeochemical Dynamics. For projects with time dependency constraints, such as natural disaster monitoring, there is also the option to download near real-time data from certain sensors using the Land Atmosphere Near Real-Time Capability for EOS (LANCE) tool. And for data from NOAA’s archives, the Office of Satellite and Product Operations (OSPO) provides links to a number of different data discovery tools, including NOAA’s Comprehensive Large Array-Data Stewardship System (CLASS). In the end, there is usually more than one way to reach the same data; it’s really a question of what tools you find easiest to use and which are most relevant to your intended application.

Searchable archives are also similarly available amongst various space agencies in other countries. For example, the Japan Aerospace Exploration Agency (JAXA) hosts the Earth Observation Research Center (EORC) Data Distribution Service (DDC), and the Indian Space Research Organisation (ISRO) offers Bhuvan, the geoportal for the National Remote Sensing Centre (NRSC) Open EO Data Archive (NOEDA).

And there are also commercial archives, such as the DigitalGlobe ImageFinder, which include high resolution satellite and aerial imagery from around the globe. While images from these archives do have a price tag, given the high spatial resolution and global coverage, such imagery can be an excellent resource for many different applications.

The above compilation is but a subset of what is ultimately available for users to access. The full extent of imagery that can be obtained, particularly when considering the many secondary data resources available from individual entities and researchers, is truly astounding. Additionally, as more and more Earth observing satellites are launched, and as airborne imagery becomes more cost efficient and easier to collect, the scope and number of both government and commercial archives will continue to expand.

What will remain a challenge is for these archives to maintain robust data discovery tools that can be used access the growing volume of data, that can adapt to new sensors and new image formats, and that can integrate data across different archives. As evident above, great progress has been made in this domain, and developers continue to explore and implement new tools for managing this valuable global resource.

So get out there and put these data discovery tools to work for your project.

Black and Blue All Over – The imagery behind NASA’s marbles

NASA is well known for its astronaut program, space exploration, rockets, satellites, remote sensing, and numerous other scientific endeavors, but are you familiar with their marbles? They now come in two flavors, a blue marble and a black marble, both depicting stunning visual displays of our planet.

The blue marble portrays a daytime view of our planet as viewed from space, and the recently released black marble reveals a novel nighttime view. Both are global composites of images collected from orbiting satellites, which have been seamlessly stitched together into cohesive representations of the entire surface of the planet.  The marbles are available for you to view and download through the NASA website, either as static individual images or as rotating animations.

Blue Marble: Next GenerationBlue Marble: The original “blue marble” was a photo acquired by astronauts onboard Apollo 17 as they departed Earth on their way to the moon, 40 years ago today, on December 7, 1972. The now iconic photo of Earth has since inspired a host of similar images, acquired from both astronauts and satellites alike, as well as motivation to generate integrated image composites of the entire planet. NASA released the first of these global composites in 2002. This version of the Blue Marble was created using imagery from the MODIS sensor onboard NASA’s Terra satellite. MODIS (Moderate Resolution Imaging Spectroradiometer) is a multispectral instrument collecting measurements in 36 spectral bands (visible to long-wave infrared). But only those bands in the visible portion of the spectrum were used for the Blue Marble in order to generate a true-color likeness of the planet. An updated version of this composite, the Blue Marble: Next Generation, was released in 2005. Although similar to the previous version, and also based on imagery from the MODIS sensor, this new version has no clouds and twice the level of detail (500m pixels versus 1km pixels).

Black MarbleBlack Marble: Most recently, on December 5, 2012, NASA released its first nighttime composite of the planet, appropriately named the Black Marble. Imagery for this version was obtained from the multispectral VIIRS instrument onboard the Suomi NPP (National Polar-orbiting Partnership) satellite, launched just over a year ago in 2011. VIIRS (Visible Infrared Imaging Radiometer Suite) measures 22 spectral bands in the visible to long-wave infrared, including a panchromatic day/night band. This day/night band is particularly capable of recording images in low-light conditions, and is the source of imagery utilized for generating the Black Marble composite.

As would be expected, the imagery used to create the marbles represents the foundation for many different scientific studies. While the science behind the marbles is indeed important, their visual beauty alone is inspiring and a meaningful reminder of the interconnected nature of our planet.

For more details on NASA’s Blue Marble: http://earthobservatory.nasa.gov/Features/BlueMarble/

For more details on NASA’s Black Marble: http://www.nasa.gov/mission_pages/NPP/news/earth-at-night.html

Google Maps Goes Underwater – A fish eye view of coral reefs

Maps have come a long way in recent years, thanks in part to efforts at places like Google and Microsoft as well as the ready availability of high resolution commercial satellite imagery from companies like GeoEye and DigitalGlobe. Combine this with on-the-ground photography and the result is an amazing ability to visualize our planet in ever increasing detail.

Google has recently taken the popular ‘Street View’ functionality into the underwater realm, offering 360° panoramas of reef locations in Australia, Hawaii and the Philippines. See examples of this imagery at maps.google.com/ocean. With a viewpoint normally reserved for sea creatures and those fortunate enough to scuba dive in such locations, this imagery now provides a window into the natural wonders of the underwater realm for anyone with access to Google Maps.Google Street View - Coral Reef

The underwater imagery for this project is being acquired in a partnership between Google and the Catlin Seaview Survey, who are using an innovative underwater panoramic camera to capture these unique images. The Catlin Seaview Survey is acquiring photographic records of reef and other marine locations around the world, providing a permanent snapshot of environmental and habitat conditions at the time the photos were recorded. Thus, the imagery you see isn’t just remarkable to look at, but it also serves a valuable scientific purpose.

Underwater locations haven’t been the only stops along the way for Google’s Street View technology. As part of the Google World Wonders Project, other locations include world heritage sites around the globe, such as Stonehenge, Yosemite National Park and the Hiroshima Peace Memorial, to name a few. The Street View technology offers an interactive 360° panorama that allows users take a virtual stroll through each location as if they were there.

As imagery such as this becomes more commonplace, and accessing satellite views of our neighborhood streets grows routine, don’t let the ease of these applications fool you. There is an amazing amount of technology behind acquiring this imagery and creating these maps. There are the satellites and cameras used to acquire the data, the algorithms used to assemble the images into seamless mosaics, the web software used to deliver the imagery to the user, and the people and companies who put it all together. It’s a complex process with many years of research needed to make it a reality. It will be exciting to see what comes next.

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Images Courtesy NASA