TerraLook: Free Time Series Satellite Images for Busy People

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Image of urban flash flooding in Arlesey, U.K, 2004. Photo by Malcolm Campbell. http://commons.wikimedia.org/wiki/File:Flash_flood_-_geograph.org.uk_-_657563.jpg

Gary N. Geller

NASA Ecological Forecasting Program

Jet Propulsion Laboratory

California Institute of Technology

Pasadena, CA USA

Figure 1. The Bolavan plateau in the Dong Hua Sao reserved forest of southern Lao PDR. In the top image from 1989 the dark green area is intact forest. The lighter green area outside of the park boundary, and the patches inside the boundary, are agriculture, primarily coffee. In the middle image from 2000 the patches of agriculture have extended across nearly the entire plateau, roughly 100 square km in area. The December, 2008 image shows how the area between the patches has filled in.

Figure 1. The Bolavan plateau in the Dong Hua Sao reserved forest of southern Lao PDR. In the top image from 1989 the dark green area is intact forest. The lighter green area outside of the park boundary, and the patches inside the boundary, are agriculture, primarily coffee. In the middle image from 2000 the patches of agriculture have extended across nearly the entire plateau, roughly 100 square km in area. The December, 2008 image shows how the area between the patches has filled in.

Satellite images can be wonderfully useful for natural resource management and many other applications.åÊ Images taken at different times are particularly useful because they can reveal–and visually document–how the world has changed, facilitating a response as well as providing a useful tool for future planning.åÊ For example, Figure 1 shows agricultural encroachment into a protected forest in southern Laos.åÊ However, although NASA and the US Geological Survey have data archives that contain millions of satellite images, a variety of barriers can make access to these images difficult for many potential users.åÊ These barriers include unfamiliar formats, a large number of confusingly similar products to choose from, and complicated systems for ordering and using the datasets.åÊ Consequently, use has been largely limited to science communities with the necessary tools, expertise, and funding, even though natural resource managers, educators, development planners, students, social and field scientists, policy makers, and the general public are all interested in satellite images of Earth.

Fortunately, these access hurdles may be overcome with data and tools appropriate for these underserved communities.åÊ Google Earth, for example, is a simple and friendly tool that has had a tremendous impact on the availability and usability of satellite imagery.åÊ However, its simplicity and friendliness come with limitations: it does not provide multiple-date imagery and cannot be used for change studies; image processing and analysis capabilities are very limited; and it can be awkward to use where adequate bandwidth is not available.

TerraLook, a joint project between NASA and the US Geological Survey, provides free georeferenced images for multiple dates in a common JPEG format, and bundles them with free, open source desktop software.åÊ Together, these make satellite images and analysis capabilities available to people that lack experience with remote sensing or the resources to buyåÊ images and expensive commercial software.åÊ Although TerraLook evolved from interactions with the conservation community, it is of use to all communities that can benefit from easy access to remote sensing data, particularly when time series analysis is useful.

Some of the primary goals of TerraLook are to

‰Û¢åÊåÊåÊ Provide an easy method to search for and obtain images

‰Û¢åÊåÊåÊ Provide images with natural-looking colors, suitable for untrained users

‰Û¢åÊåÊåÊ Use a common, compressed image format

‰Û¢åÊåÊåÊ Georeference all images

‰Û¢åÊåÊåÊ Work with many existing tools

‰Û¢åÊåÊåÊ Provide optional, open-source software that is simple and intuitive to use

‰Û¢åÊåÊåÊ Support images files, vector files, change analysis, annotation, and common image processing and GIS capabilities

TerraLook Overview

TerraLook has three major components: a website at USGS where users can find and order the images of interest, the image collections that USGS then generates and the user downloads, and the (optional) desktop software that helps the user interact with the images.åÊ The USGS, at its Data Center for Earth Resources for Observations Systems, operates the website and began offering TerraLook products in early 2007.åÊ Their Global Visualization Viewer (GloVis) is used to select the scenes to include in an image collection.åÊ Available image sources currently include all acquired ASTER data–about 1.5 million images and with about 500 new images every day (ASTER is a space-based digital camera that began operations in 2000, with 15m spatial or ground resolution, a 60 km swath width, and a variable repeat cycle).åÊ Historical images are provided by the Landsat orthorectified tri-decadal datasets from c. 1975, 1990, and 2000.åÊ Also known as the “GeoCover” datasets, each of these provides a single layer of high quality images with global coverage (Landsat resolution is about 80m for 1975, and 30m for 1990 and 2000; swath width is 180 km).åÊåÊåÊ After the user selects the scenes the automated system creates a collection of georeferenced JPEG images and makes it available for download.åÊ A collection can contain one, or hundreds of images.åÊ Most users create a collection around a particular theme, such as a country, a watershed, or the parks of a particular area.

The desktop software is a free and open source image processing and GIS tool, which was developed using existing open source image processing software called OpenEV.åÊ Major capabilities include:

‰Û¢åÊåÊåÊ Image enhancement

‰Û¢åÊåÊåÊ Image find, roam, and zoom

‰Û¢åÊåÊåÊ Distance and area measurement

‰Û¢åÊåÊåÊ Display, edit, and create overlays

‰Û¢åÊåÊåÊ Image annotation (adding text, arrows, etc,)

‰Û¢åÊåÊåÊ Image comparison using “flicker”

‰Û¢åÊåÊåÊ Image mosaicking

‰Û¢åÊåÊåÊ Attribute table editing and other basic GIS functions

‰Û¢åÊåÊåÊ 3-D viewing capability (basic)

‰Û¢åÊåÊåÊ Multilingual–English, Spanish (plus French menus but not Help)

The TerraLook website explains how to create a new TerraLook collection using GloVis.åÊ In addition, the site provides several use case examples of how TerraLook can be used and has tutorials that can be downloaded.åÊ A link is provided to SourceForge, an open source repository and website from where the TerraLook software can be downloaded.åÊ There is also a link to the ASTER website containing archived collections for about 30 countries and a variety of other themes.åÊ These archived, downloadable collections, while not global in coverage, provide an easy way to obtain full-country coverage of many countries without having to order the data (Note: good bandwidth is required as the collections are generally quite large).


Satellite images are useful for many types of natural resource management, including planning, development, and sustainable management of forests, grasslands, and agricultural areas.åÊ They are also useful in urban studies, infrastructure development, and other disciplines. Satellite images make wonderful education tools—analyzing change is an excellent method to teach and practice critical thinking, and helps students recognize and appreciate that the world is changing.åÊ All these groups face similar access hurdles and TerraLook can be a great help in overcoming them.

Figure 2. Land use change near the confluence of the Parana and Iguazu Rivers (Argentina, Brazil, Paraguay).

Figure 2. Land use change near the confluence of the Parana and Iguazu Rivers (Argentina, Brazil, Paraguay).

TerraLook has global coverage and users have come from all continents except Antarctica.åÊ Because of its origin in the conservation community most TerraLook users have been engaged in some sort of conservation activity, including detecting, mapping, and managing land use change such as deforestation; classifying vegetation and land use; threat detection and management such as boundary encroachment; mapping burn scars; and simply understanding spatial relationships.åÊ This user base is expanding to other groups that are similarly underserved, especially educators and students, and groups in developing countries such as those doing other types of natural and agricultural resource management, and infrastructure development.

Figure 2 provides another example of how TerraLook can be used.åÊ The area near the confluence of the Parana and Iguazu rivers, near the junction of Argentina, Brazil, and Paraguay, has seen tremendous change between 1973 and 2000.åÊ The Itaipu dam was completed in 1982, resulting in the formation of Lake Itaipu behind it on the Parana River.åÊ Throughout much of the area forest was converted to agriculture, which sometimes was further converted by urban expansion around the twin cities of Foz do Igua̤u in Brazil, and Ciudad del Este in Paraguay.åÊ The protected areas surrounding Iguazu Falls remained forested, and reforestation can be observed on the Brazilian side (center-right of each image).

User Feedback

TerraLook has been an effort driven and guided by the users, including: UNESCO; UNEP-WCMC; IUCN; OAS/Amazon Protected Area Network and their NGO and government partners; Uganda Wildlife Authority; Serengeti National Park; Wildlife Conservation Society; The Nature Conservancy; Mekong River Commission; Malaysian Nature Society; US State Department; US National Park Service; US Fish and Wildlife Service; Central America Regional Monitoring and Visualization System (SERVIR); and Cambodian Mine Action and Victims Assistance Authority.åÊ Additionally, TerraLook was one of three finalists for the 2007 St. Andrews Prize for the Environment.

Some user comments:

“Many thanks‰Û_for providing this invaluable information.åÊ It will prove to be a fantastic tool in the fight to protect the earth’s wild places. It has already proved its value in this particular case.”åÊ —user from a large conservation NGO

“Keep pushing to get the images in the hands of the practitioners.åÊ It’s the greatest contribution NASA could make to protected area managers.” —former superintendent of one of the largest US National Parks

“‰Û_Not even the chiefs of the sanctuaries in the border area get better and newer satellite images‰Û_” —conservation practitioner in Thailand

Next Steps

There is still much to do.åÊ One area with much activity is the development of Version 2 of the software.åÊ This will be a major upgrade, completely overhauling the software’s look, feel, and usability, and requiring a change in the underlying Graphic User Interface management software.åÊ Several additional capabilities will be added, such as the ability to edit collections, and an Identify function.åÊ Release is planned for late 2009.åÊ The other major area of work is outreach, so that the many potential users in “non-traditional” groups are aware of TerraLook and encouraged to use it.åÊ In addition to expansion of the tutorials, regional and local organizations are being engaged as liaisons between TerraLook and end users.åÊ These liaisons, large and small, can act as hubs to disseminate information, distribute collections, assist users, and foster education activities on use of images.åÊ Two such hubs are located in Latin America.åÊ One is the World Bank-sponsored IABIN project, and the other is the NASA/USAID-sponsored SERVIR project.åÊ Hubs can be of any size or focus, and key hub partners are being solicited, mostly at the regional scale (all are welcome).åÊ In-country capacity-building workshops are ongoing, focused on the use of satellite images for conservation and sustainable development.


This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology.åÊ At USGS, this project was made possible with the collaboration and support of the USGS Land Remote Sensing program.åÊ The U.S. space agency, NASA (particularly the ASTER Science Project), and USGS/EROS are the prime agents supporting development.åÊ The Toolkit was developed by Ecollage, a conservation NGO, with funding from the World-Bank-funded IABIN Project and the NASA/USAID funded SERVIR project.åÊ Other sponsors include The Nature Conservancy, IUCN-The World Conservation Union, and the United States Department of State.