Whether by looking at satellite images of landscapes or finding their house on Google Earth, most people in the United States have had some experience with the products of remote sensing. This key geospatial technology, which includes satellite imagery and aerial photography, is used to make, correct, and enhance maps of all kinds. Professional uses range from monitoring the melting of polar ice or the effects of drought in the Farm Belt or outbreaks of infectious diseases to showing the devastation wrought on villages in Darfur by the Janjaweed militia or the development of new missile bases in North Korea, from finding buried pyramids to monitoring the ripening of wine grapes.
Remote Sensing
Remote sensing is the acquisition of information about an object or phenomenon via any sensing device that is not in physical contact with it. By analogy, our eyes, ears, and noses are means of remote sensing, while our tongues and our skin are not (except for our skin’s ability to detect remote sources of irradiated heat, such as a heating lamp). In the geospatial context, remote sensing refers mainly to Earth observation from satellite- and aircraft-based digital cameras. These are “passive” devices, in that they detect radiation emitted or reflected by surfaces — mostly sun light reflected by the bare ground, by bodies of water, or by land cover, such as grass, trees, or buildings. Geospatial remote sensing also includes “active” devices, such as radar, LIDAR (light detection and ranging), and sonar, that first emit energy and then collect it as it is reflected or backscattered by their target. Remote sensing enables the collection of data on dangerous or inaccessible areas without disturbing the areas being surveyed. The main advantage of remote sensing, however, is that it is much cheaper and more efficient than ground surveying for gathering data on large areas. For example, monitoring global climate change and pollution can only be done effectively by remote sensing.
While most data from satellites are in image form, the field of remote sensing does not deal exclusively with image processing. Sophisticated mathematical approaches to signal processing also contribute significantly in extracting information from the remotely sensed waveforms or time series data. In fact, remote sensing is very much an interdisciplinary area of scientific investigation, and relies in large part on knowledge of physics (including optics), electronics engineering, mathematics, chemistry, and geography.
The following brief round-up of recent developments in remote sensing shows the current importance and future promise of this geospatial technology.
New Birds
The widespread availability of satellite imagery, especially through Google Earth, has led to an explosion in public usage. This, together with continued demand for imagery by governments in the United States and worldwide, has fueled an increase in the number of remote sensing satellites — or “birds” as they are called in the jargon of the trade. I expect this positive feedback cycle to continue for the next several years.
- On September 6, GeoEye launched GeoEye-1, which has a resolution of .41 meters — the highest of any commercial imaging system — and a geographic accuracy of about three meters. The satellite makes 15 polar orbits per day and is able to revisit any point on Earth every three days or sooner. In its panchromatic (black and white) mode, every day it collects an area about the size of Texas; in its multispectral mode, every day it collects an area about the size of New Mexico. The National Geospatial-Intelligence Agency (NGA) paid half of the $475 million cost of the satellite.
- On October 22, India launched Chandrayaan-1, a lunar probe aimed at high-resolution remote sensing of the moon in visible, near-infrared, low energy X-rays, and high-energy X-ray regions. The craft is intended to orbit the Moon for two years, send an impactor to the surface, and use remote sensing to produce chemical and topographical maps. The mission is India’s bid to keep up with China, Japan, and South Korea in the new Asian space race. However, for more than 20 years, India has been using space technologies to solve the everyday problems of its people — investing hundreds of millions of dollars in its earth-sciences program with an eye toward helping farmers with their crops, fishermen with their catches, and rescue workers with management of floods and other disasters. Its seven remote sensing satellites have sub-meter resolution and cost about $500 million each, or a tenth of the cost of its Western counterparts.
- On October 24, a Delta 2 rocket launched from Vandenberg Air Force Base in California deployed COSMO-Skymed 3, the third in a series of Italian remote sensing satellites, into a Sun-synchronous orbit. The spacecraft was built by Thales Alenia Space Italia for the Italian Space Agency. A fourth satellite is planned for launch in 2010.
- On November 26, the Operational Land Imager being built by Ball Aerospace & Technologies Corp. for the Landsat Data Continuity Mission, the eighth in the Landsat satellite series, successfully passed the Instrument Critical Design Review, a key milestone toward full operational status. The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey (USGS). For more than 36 years, Landsat satellites have continuously and consistently collected multispectral imagery of Earth, creating a historical archive unmatched in quality, detail, coverage, and length that is widely used for, among other things, agricultural monitoring, natural resource management, and land-use planning.
- On December 1, China launched the Yaogan-4 remote sensing satellite developed by the China Academy of Space Technology, according to which the satellite will be used for scientific research, land resources surveying, crop yield estimate, and disaster prevention and relief. However, the satellite could also be used for a range of military reconnaissance applications.
- In mid-2009, Digital Globe will launch WorldView-2, which will enable the company to offer half-meter panchromatic resolution and 1.8-meter multispectral resolution with an average revisit time of one day and a coverage of up to 975,000 square kilometers (376,000 square miles) per day. According to the company, “Added spectral diversity will provide the ability to perform precise change detection and mapping. WorldView-2 will incorporate the industry standard four multispectral bands (red, blue, green and near-infrared) and will also include four new bands (coastal, yellow, red edge, and near-infrared 2).”
- The Indian Space Research Organization is building a small launcher that costs 40 percent less than existing rockets to hurl into low-Earth orbit remote-sensing satellites weighing less than 500 kilograms.
I should also note, however, one step in the opposite direction: the U.S. Congress recently cancelled the BASIC (Broad Area Space-Based Imagery Collection) program, an effort by the National Reconnaisance Office (NRO) to obtain two Earth-observing remote sensing satellites with a resolution of 1.1 meter at a cost of $1.7 billion.
Conferences and Journals
On October 27 to 31, in Accra, Ghana, the 7th international conference of the African Association of Remote Sensing and the Environment (AARSE) took place to map out strategies for using remote sensing to manage regional environmental resources. The topics covered in the four-day conference included forest monitoring, risk management, and agriculture. The 600 participants included experts in remote sensing from the International Society of Photogrammetry and Remote Sensing (ISPRS), the Institute of Electrical and Electronic Engineers (IEEE), the Geo-science and Remote Sensing Society (GRSS), and the Global Earth Observation System of Systems (GEOSS).
The Institute of Electrical and Electronics Engineers has launched a new publication: the IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing that covers current issues and techniques in applied remote sensing, their integration, and applied modeling and information creation for understanding the Earth, oceans, and atmosphere. Topics include observations, derived information such as forecast data, simulated information, data assimilation and Earth information techniques to address science and engineering issues of the Earth system. The inaugural issue of the journal proposed new ways of dealing with energy, particularly renewable energy, by taking advantage of all the benefits that Earth observations and remote sensing provide.
Novel Applications
Researchers in an ever-expanding number of fields are realizing how remote sensing can help them. Here are two recent examples:
- Professor Margaret Kalacska of McGill University in Quebec, Canada, has been examining how remote sensing can help identify clandestine burials. By studying the spectral profile of mass animal graves she is learning to use changes in soil chemistry that resulted from decomposition to differentiate between empty graves and graves full of carcasses. Once perfected, this technique will be immensely valuable to forensic archaeologists looking for mass graves in areas that are, or have been, the site of massacres, such as in Cambodia, Rwanda, Sudan, and the former Yugoslavia.
- By applying algorithms they developed to optimize hi-resolution infrared and multispectral images from the Quickbird satellite, Nicola Masini and Rosa Lasaponara, of Italy’s National Research Council, were recently able to “peel away” layers of mud and rock near Peru’s Cahuachi desert to reveal an ancient adobe pyramid extending over a 9,000-square-meter area.
Earth Cam
The French Space Agency, CNES (Centre National d’Etudes Spatiales), has developed e-CORCE, an innovative satellite remote-sensing system capable of generating a high-resolution picture of Earth on the Web, refreshed every week. In contrast with Google Earth, whose imagery varies greatly in resolution from one area to another and is updated as new imagery becomes available, by 2014 e-CORCE, according to CNES, will be able to photograph all of the continents in color at a 1-meter resolution every week, using a constellation of 13 Earth-orbiting microsatellites at 600 kilometers, imaging everything in their path and down-linking compressed data to processing centers around the world, which will each handle a slice of the data, then make it all accessible over the Internet. If this vision is realized, it will allow everybody with a computer and Internet access to monitor changes on Earth in near-realtime.
A few years ago, I suggested to GeoEye that it devote a small amount of its bandwidth to downloading a continuous image stream from its satellites, for broadcast over the Internet. Unfortunately, they didn’t take me up on my Earth cam idea. However, e-CORCE will be far better.
What’s Next?
Finally, here’s my pick for the next big thing in remote sensing: consumer-grade automated feature extraction software, coupled with the wide availability of free satellite imagery, will enable new businesses. For example, you could easily identify and locate all the swimming pools in the Los Angeles area and sell the data to pool cleaning companies — or set one up yourself and start making the rounds.
By: Matteo Luccio, President, Pale Blue Dot Research, Writing, and Editing, LLC
