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Posts Tagged ‘remote sensing’

Accessing Landsat 8 Data through DevelopmentSeed’s Libra Portal

Libra is a very useful browser for open Landsat 8 satellite imagery. You can use it to browse, filter, sort, and download imagery for the entire planet.  Libra was developed by DevelopmentSeed, an engineering team solving complex problems with open software and open data, and AstroDigital, a company focused on providing imagery analyzed in real time and streamed to applications via their API.

Libra’s map interface is one of the most straightforward and useful that I’ve ever seen for imagery as evidenced in the screenshot below.  On the interface, each circle on the map represents the number of available images at that location. Filters at the top of the map can be used to select a date range, cloud cover percentage, and sun azimuth angle. Bundled downloads are available within one week of the image being taken. Individual bands are available for all 2015 scenes.

Once your download is complete, the site organizers recommend Landsat-util for processing the raw image and getting it ready for publication and analysis.  Search results are powered by Landsat 8 Metadata API and images from USGS Earth Explorer. Downloads are provided via Google Earth Engine and Amazon Web Services.

More information and the official announcement about this resource can be found here.   Give it a try and let us know what you think.

Interface for the Libra Development Seed Landsat Site.

Interface for the Libra Development Seed Landsat Site.

New LandViewer Tool for Quickly Finding and Analyzing Satellite Imagery

The LandViewer tool and data portal quickly and painlessly allows you to browse and access satellite imagery for the planet.  The tool, developed by the Earth Observing System Inc.’s Max Polyakov, currently features Landsat 8 and Sentinel 2 imagery with more image sets soon to arrive.  Landsat 8 carries two instruments: The Operational Land Imager (OLI) sensor includes refined heritage bands, along with three new bands: a deep blue band for coastal/aerosol studies, a shortwave infrared band for cirrus detection, and a Quality Assessment band. The Thermal Infrared Sensor (TIRS) provides two thermal bands. Sentinel 2 is an Earth observation mission developed by the ESA as part of the Copernicus Programme to perform terrestrial observations in support of services such as forest monitoring, land cover changes detection, and natural disaster management.

Using the LandViewer tool, you can quickly zoom on an interactive web map to your area of interest.  You can filter on geography and time, including cloudiness, sun angle, and other parameters. At the time of this writing, 18 filters such as Atmospheric Removal, Panchromatic, NDVI, Thermal Infrared, False Color, and more, are available so that you can obtain the band combinations most suitable to your analysis in the areas of agriculture, geology, or other applications. A very helpful image interpretation screen is available to help you choose the combination that are best for your analysis goals.  You can do some contrast stretching in the web tool itself.  Then after signing in to the site, you can download the images in GeoTIF for further analysis using your favorite GIS tools.

The tool was also reviewed on the Geoawesomeness web site, and I wholeheartedly agree with their sentiments expressed–this is one of the most useful and fastest satellite image portals I have used. It is useful for research but also, given its ease of use, can even be used effectively to teach concepts of remote sensing.  Give it a try and let us know in the comments section what you think.

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Landsat scenes with band combinations possible for an area on the southwest side of Costa Rica.

 

Enhancements to Landsat Thematic Bands Web Mapping Application

November 6, 2016 Leave a comment

Last year, we wrote about the Landsat Thematic Bands Web Mapping Application, an easy-to-use but powerful teaching and research tool and data set. It is a web mapping application with global coverage, with mapping services updated daily with new Landsat 8 scenes and access to selected bands that allows the user to visualize agriculture, rock formations, vegetation health, and more.  The Time tool allows for the examination of changes over years, over seasons, or before and after an event.  The identify tool gives a spectral profile about each scene.  I have used this application dozens of times over the past year in remote sensing, geography, GIS, and other courses and workshops, and judging from the thousands of views that this blog has seen, many others have done the same thing.

If that weren’t all, the development team at Esri has recently made the tool even better–one can now save a time sequence or a band combination as a permanent URL that can be shared with others.  The flooding of 20 districts in August and September 2016 in Uttar Pradesh, India, for example, can be easily seen on this link that uses the application, with screenshots below.

Another example is the Fort McMurray summer 2016 wildfire in Alberta, Canada  – the user can change the time to see the region’s vegetation cover before and after fire, and the extent of the smoke during the fire.  Or, you can analyze a different band combination, as is seen here.

To do this, open the application.  Note that the application URL has been updated from the one we wrote about last year.  Move to an area of interest.  Select any one of the available thematic band renderers (such as agriculture, natural color, color infrared, and others available), or create your own band combination using build.  Then, turn on “time” to see your area of interest at different periods using your band combination.  Next, share this image with other people.   Simply click on any one of the social platforms (Facebook or Twitter) in the upper right, which will create a short link that can be shared.  When the person you send this link to opens it, the Landsat app will open in exactly the same state it was in before social platform tool was clicked.  Give it a try!

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Landsat 8 Image for Allahabad India on 31 May 2016.

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Harmonising UAS Regulations and Standards: Article Review

October 23, 2016 Leave a comment

A recent article in GIM International about harmonising UAS (Unmanned Aerial Systems, or UAVs (Unmanned Aerial Vehicles), or “Drone” technologies) regulations and standards is definitely worth reading, providing an excellent summary of this rapidly evolving sector of the geospatial industry.  The article, beginning on page 6, is in a special issue of GIM International dedicated exclusively to UAS, available here.  Peter van Blyenburgh summarizes developments in regulations and standardization in Europe, the USA, Japan, and China, and then provides some down-to-earth advice for companies who are seeing the potential for profits only but may not see the bigger picture about liability, regulations, and safety.  The GIM issue also includes articles about integrating UAS and multibeam echosounder data, multispectral and thermal sensors on UAVs, UAS applications in agriculture, and the article “Airborne laser scanning” provides an excellent introduction to the two main platforms:  fixed-wing and rotorcraft.

If I am reading the “tea leaves” correctly, in the world of education, just about every GIS program offered at a technical college and university will include at least one course in UAS technology and data by this time next year.  And I would expect that a whole host of online MOOCs and other courses will appear from universities, companies, and GIS organizations to help people effectively use these new tools and technologies.  I attended, for example, a multi-hour course at the recent Geo’Ed community college GIS conference on this topic.  This reinforced my opinion that while online courses and programs will be helpful, the face-to-face component, actually working with the software and hardware, is particularly useful when working with UAS:  There is no perfect substitute for rolling up one’s sleeves and working with these devices.

As publishing director Durk Haarsma states in his editorial for this special issue, UASs are disruptive technologies, because they are influencing so many geospatial fields and subfields, such as cadastral surveying, cultural heritage, and precision agriculture, just to name a few.  Because UAS influence how people in an increasing number of professions map and model the world, interpreting the data from those UAS is central to our book and this blog–understanding your data, and how they are obtained, is more critical than ever.

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Launching a fixed wing UAV at the Geo’Ed conference, Louisville Technical College, Kentucky. Photograph by Joseph Kerski.  Video here and analyzing thermal imagery here.

Landsat Thematic Bands Web Mapping Application in ArcGIS Online

December 20, 2015 2 comments

Teaching remote sensing?  Or just want to understand remotely sensed imagery better?  The Landsat Thematic Bands web mapping application can serve as a very useful teaching, learning, and research tool.  It covers the entire planet and the map is updated daily with new Landsat 8 scenes.

You can access many band combinations and indices by hovering over the tools to the left of the map image and selecting among the following:

  • Agriculture: Highlights agriculture in bright green. Bands 6,5,2
  • Natural Color: Sharpened with 25m panchromatic band. Bands 4,3,2+8
  • Color Infrared: Healthy vegetation is bright red. Bands 5,4,3
  • SWIR (Short Wave Infrared): Highlights rock formations. Bands 7,6,4
  • Geology: Highlights geologic features. Bands 7,4,2
  • Bathymetric: Highlights underwater features. Bands 4,3,1
  • Panchromatic: Panchromatic image at 15m. Band 8
  • Vegetation Index: Normalized Difference Vegetation Index (NDVI). (Band5-Band4)/(Band5+Band4)
  • Moisture Index: Normalized Difference Moisture Index (NDMI). (Band5-Band6)/(Band5+Band6)

The Time tool for different indices at larger scales based on a user-selected location enables examination of changes over years or over seasons.  It also provides temporal profiles for NDVI (Normalized Difference Vegetation Index), NDMI (Normalized Difference Moisture Index) and an Urban Index, dating back to 1973.  The Identify tool enables access to information on the date, cloud cover, and a spectral profile about each scene.  The Bookmark tool allows access to interesting locations such as the “Eye of the Sahara” in Mauritania.

The application is written using Web AppBuilder for ArcGIS accessing image services using the ArcGIS API for JavaScript, with access to the following Image Services:

  • Landsat Multispectral on AWS – 8-band multispectral 30m resolution image services and functions that provide different band combinations and indices.
  • Landsat Pan-sharpened on AWS – Panchromatic-sharpened imagery; 4-band (Red, Green, Blue and NIR); 30m resolution.
  • Landsat Panchromatic on AWS – Panchromatic imagery; 15m resolution.

These services can also be accessed through the public Landsat on AWS group on ArcGIS Online.  Because you can add these services as layers to your own maps or are adding to maps made by others, or if you are simply using the above web mapping application as a standalone map, you truly have “the world at your fingertips” with these maps and apps.  But there is a third option: Use the Unlock Earth’s Secrets page, also useful for instruction, with the above application embedded in it, but also with explanatory text and featured places around the planet as they have changed through time.

Think of the above as solid introductory segments to help your students, customers, or stakeholders see the value in remote sensing.  These maps and applications require very little geospatial technology skills to use, but allow you to focus on building remote sensing concepts and principles while exploring some truly engaging content and places.

To dig deeper, delve into the many powerful remote sensing functions available in ArcGIS Desktop.  One source for engaging, hands-on activities, is Kathryn Keranen and Bob Kolvoord’s book Making Spatial Decisions Using GIS and Remote Sensing:  A Workbook.

Give these resources a try!

Landsat web application

Landsat web application in ArcGIS Online.

Landsat 8 Data Now Available on Amazon AWS

April 13, 2015 Leave a comment

Last month Amazon announced the release of Landsat 8 data on its AWS S3 platform. The data are freely available in GeoTiff format and are not subject to any restrictions on use. The imagery is updated on a 16 day cycle and is available on AWS within hours of reception by USGS.

All of the scenes from 2015 are available, along with a selection of scenes from 2013 and 2014. For those interested in downloading the data (no Amazon account required), each scene’s directory includes the following:

  • a .TIF GeoTIFF for each of the scene’s up to 12 bands
  • .TIF.ovr overview file for each .TIF
  • a _MTL.txt metadata file
  • a small rgb preview jpeg, 3 percent of the original size
  • a larger rgb preview jpeg, 15 percent of the original size
  • an index.html file including the RGB preview and links to the GeoTIFFs and metadata files

As a partner in the initiative to provide easier access to the imagery, Esri has created a set of Landsat Web Services that are available through ArcGIS Online. The services provide dynamic access to the entire collection of Landsat 8 data on AWS.  The web services show one Landsat 8 service that has a subset of the Landsat 8 imagery. If you are interested in downloading more, see the “downloading” link  here.

Cambridge Gulf in Australia

Cambridge Gulf in Australia

 

 

 

UAVs Prohibited in National Parks in the USA

November 10, 2014 2 comments

As we state in our book, The GIS Guide to Public Domain Data, oftentimes, technological advancement and adoption proceeds at a faster pace than regulations accompanying it.  A perfect example is what is probably the hottest technology in remote sensing right now, and that is UAVs, or Unmanned Aerial Vehicles.  The Internet is becoming rapidly filled with stories and videos of footage from UAVs deployed by aerial survey companies, but even more commonly, operated by the general public.  For example, this storymap contains footage of UAV imagery flown over a rocket launch, a cruise ship, and more.

While I as a geographer are fascinated by these images and videos, I am at the same time sensitive to the myriad of privacy and safety issues raised by the operation of UAVs.  We are beginning to see laws passed to regulate the operation of UAVs on certain lands, such as the recent policy directive against flying these in national parks in the USA.

Jonathan Jarvis, director of the National Park Service, said that “We embrace many activities in national parks because they enhance visitor experiences with the iconic natural, historic and cultural landscapes in our care.  However, we have serious concerns about the negative impact that flying unmanned aircraft is having in parks, so we are prohibiting their use until we can determine the most appropriate policy that will protect park resources and provide all visitors with a rich experience.”  Some parks had already initiated bans after noise and nuisance complaints from park visitors, an incident in which park wildlife were harassed, and park visitor safety concerns.  For example, earlier this year, visitors at Grand Canyon National Park gathered for a quiet sunset were interrupted by a loud unmanned aircraft flying back and forth and eventually crashing in the canyon. Volunteers at Zion National Park witnessed an unmanned aircraft disturb a herd of bighorn sheep, reportedly separating adults from young animals.

The policy memorandum directs park superintendents to take a number of steps to exclude unmanned aircraft from national parks. The steps include drafting a written justification for the action, ensuring compliance with applicable laws, and providing public notice of the action.  The memorandum does not affect the primary jurisdiction of the Federal Aviation Administration over the National Airspace System.

The policy memorandum is a temporary measure, and it seems like a wise move. Jarvis said the next step will be to propose a Servicewide regulation regarding unmanned aircraft. That process can take considerable time, depending on the complexity of the rule, and includes public notice of the proposed regulation and opportunity for public comment.  The National Park Service may use unmanned aircraft for administrative purposes such as search and rescue, fire operations and scientific study. These uses must also be approved by the associate director for Visitor and Resource Protection.

Near the Esri office in Colorado a month ago, I witnessed my first UAV flight where I did not know who was operating the vehicle.  I’m sure we will look back in years to come and realize that we in 2014 were at the dawn of a technology that will no doubt transform GIS and our everyday lives.   I anticipate sensors soon capable of capturing imagery in a wide variety of wavelengths, as well as atmospheric and other types of sensors that will further hasten the era of big data.  I am hopeful that we will chart a prudent course through the advent of UAVs, taking advantage of the innumerable benefits that UAVs can offer the GIS industry and also society as a whole.