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Archive for May, 2007

Characterization of Satellite Remote Sensing Systems

Thursday, May 31st, 2007

The most common characterization of different remote sensing (RS) satellite imaging systems results from the systems diverse spatial, temporal and spectral resolutions.

Spatial Resolution

The spatial resolution specifies the pixel size of satellite images covering the earth surface.

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High spatial resolution: 0.6 – 4 m
Medium spatial resolution: 4 – 30 m
Low spatial resolution: 30 – > 1000 m

Temporal Resolution

The temporal resolution specifies the revisiting frequency of a satellite sensor for a specific location.

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IKONOS Satellite Temporal Resolution

High temporal resolution: < 24 hours – 3 days
Medium temporal resolution: 4 – 16 days
Low temporal resolution: > 16 days

Spectral Resolution

In the first instance, a sensor’s spectral resolution specifies the number of spectral bands in which the sensor can collect reflected radiance. But the number of bands is not the only important aspect of spectral resolution. The position of bands in the electromagnetic spectrum is important, too.

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Electromagnetic Spectrum

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Spectral Resolution for Landsat TM7 and ASTER Satellite Sensors

High spectral resolution: – 220 bands
Medium spectral resolution: 3 – 15 bands
Low spectral resolution: – 3 bands
Resolution Trade-Off

The different spatial, temporal and spectral resolutions are the limiting factor for the utilization of the RS data for different applications.

Unfortunately, because of technical constraints, satellite RS systems can only offer the following relationship between spatial and spectral resolution: a high spatial resolution is associated with a low spectral resolution and vice versa.

That means that a system with a high spectral resolution can only offer a medium or low spatial resolution.

Therefore, it is either necessary to find compromises between the different resolutions according to the individual application or to utilize alternative methods of data acquisition.

The trade-off may result in two different solutions:

  • To lay emphasis upon the most important resolution, in direct dependency to the application, with the acceptance of low attendant resolutions at the same time, or
  • To lay no emphasis on one specific resolution and at the same time the acceptance of a medium spectral, temporal and spatial resolution.

In most cases of the planning task, functions need regular local or regular regional data with a high spectral resolution as well as a medium or high spatial for planning functions, the resolution problem, i.e. a high spectral and ideally a high spatial resolution, is evident.

According to the above mentioned solutions for the resolution problem, the following sensors are recommended for the acquisition of RS data:

EO-1 (Hyperion) offers the highest quality data in 220 spectral bands

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QuickBird – offers satellite image data in 5 bands (Red -Green-Blue-Pan-NIR)

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SPOT-5 neither spatial nor spectral resolution has to be as high as possible is the first of the high resolution satellites to truly balance large scene sizes with highly detailed imagery and a relatively high spatial resolution, with coverage of vast territories: scenes of 60 x 60 or 60 x 120 km.

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Resources:

Satellite Imaging Corporation – Providers of high resolution satellite images, aerial photos, GIS mapping and DEMs for industry mapping applications.

Satellite Image Captures F5 Tornado Damage in Greensburg, Kansas

Tuesday, May 29th, 2007

Satellite image captured the tornado damage and devastation in Greensburg, Kansas – Population of 1,398 was hit by an F5 Tornado on May 4th, 2007 at 9:45 pm killing 7 people. The most powerful tornado to hit the US in eight years demolished every business, church and home in site. The neighborhoods were left unrecognizable. The F5 tornado was recorded to have had winds of 200 mph and carved a track of about 1.7 miles wide and traveled a distance of 22 miles non-stop for 30 minutes.

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IKONOS – Greensburg, Kansas

F5 Tornado Damage and Tornado Track

May 5, 2007

Copyright © 2007 Geoeye. All Rights Reserved.

Satellite remote sensing from high resolution satellite sensors such as QuickBird (0.6m) and IKONOS (0.8m) can provide accurate and detailed information on the damage occurred in order to access the damage and determine the recovery from natural disaster.

Satellite images can provide and represent significant changes in the land cover resulting from damaged vegetation and large debris fields from multispectral satellite image data from satellite sensors such as Landsat and Aster which reveal tracks the tornado damage in the aftermath of the destruction in order to access the damage and costs of recovery.

Satellite Images are the most powerful and important tools used by meteorologists, emergency management and government agencies. These images reassure forecaster to the behavior of the atmosphere as it gives clear and accurate information on the location of the storms. Satellite images aid in showing what cannot be measured or seen by the naked eye.

Resources:

Satellite Imaging Corporation – Provider of high resolution satellite imagery, aerial photography, GIS mapping and DEMs for various industries.

Geoeye – IKONOS satellite data provider

Satellite Imagery for 2007 Hurricane Season

Thursday, May 24th, 2007

US Government issued a storm warning for the year 2007 hurricane season and claimed that 13 to 17 named storms, seven or 10 of which are expected to become hurricanes that will hit the Atlantic. Weather forecasters predict that 3 to 5 will be major at a category 3 or higher and putting the Gulf of Mexico at high risk of getting hit by 6 to 7 hurricanes . The hurricane season typically peaks between 1 August and late October.

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Satellite Image of Hurricane Rita

Image Credit: NASA

County planners, coastal managers and local communities can better prepare for the next natural disaster by learning from past experiences. Satellite imagery and GIS mapping enables emergency management and community planners to better prepare for hurricane impacts on their region. Estimates of the particular land cover classes that may be inundated by each category hurricane can enable planners to better assess the region’s vulnerability. With this type of information, planners are better able to prioritize and target mitigation and preparedness activities for their area. Remote sensing gives state and government agencies the ability to view the damage from multiple vantage points. The spatial resolution of an image determines the ability to view individual features such as building’s and bridges. It also effects the ability to monitor and access damage conditions and depends on the nature of the hazard itself – for example: flooding, wind-pressure and storm surges.

Using high resolution satellite images of 1 meter or less from satellite sensors such as QuickBird and IKONOS are necessary to distinguish the damage conditions of individual buildings such as wind damage to roofs and escape routes. Image resolution of 10 meter or smaller can determine the discern presence and location of the buildings and detect and monitor flooding. Satellite imagery from multispectral satellite sensors such as Landsat and ASTER can detect difference in physical materials such as vegetation, construction materials and water by identifying their unique characteristics which is beneficial to separating the constituent materials within an image and for the interpretation of images for pre and post disaster assessment.

Hurricane Katrina Pre and Post Hurricane, New Orleans, USA, September 2005:

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Satellite Photos Copyright © 2007 Geoeye . All Rights Reserved.

Resources :

Satellite Imaging Corporation

Geoeye

NASA

Satellite Image Radar Captures Giant 36 ft. Wave That Hit Reunion Island

Wednesday, May 23rd, 2007

SAR Image – Reunion Island, Indian Ocean

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To view animation of the Giant Wave caught by SAR:

http://www.esa.int/esaEO/SEMAKIV681F_economy_0.htmlA typical SAR satellite images a swath of 400 km, enough to capture complete ‘mesoscale’ phenomena such as tropical storms:

A giant 36ft. wave was caught by a satellite imaging radar when it thrashed the southern port of Saint Pierre, Reunion Island on Saturday evening sending piers crashing down and flooding homes along the coastline. Two fishermen were still reported missing after their boat capsized.

Thought to be only legendary but now a natural ocean phenomenon, not rare, but rarely encountered. Evidence from mariners’ claimed that disappearances and damages to large ocean vessels suggests they have occurred. This evidence was confirmed following measurements of a massive wave at the oil platform in the North Sea in 1995. which caused minor damage was inflicted on the platform, confirming that the reading was valid.

Researchers from the GKSS Research Centre, using data collected by ESA satellites, identified a large number of radar signatures that may be evidence for rogue waves. Further research verifies the method that translated the radar echoes into sea surface elevation.

Freak waves or rogue waves have been cited in the media as a likely source of the sudden unexplainable disappearances of many ocean vessels.

The animated image (above link) was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on October 5, 1994. The image is centered at 21.2 degrees south latitude, 55.6 degrees east longitude. The area shown is approximately 50 km by 80 km (31 miles by 50 miles). North is toward the upper right. Colors are assigned to different frequencies and polarizations of the radar as follows: red is L-band horizontally transmitted, vertically received; green is L-band horizontally transmitted, vertically received; and blue is C-band horizontally transmitted, vertically received. SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA’s Mission to Planet Earth. Envisat is equipped with an advanced version of the SAR instrument, Advanced Synthetic Aperture Radar (ASAR), flown on the ERS-1 and ERS-2 missions. Its wave mode acquires 10 by 5 km small images, or ‘imagettes’, of the sea surface every 100 km along the satellite orbit. These small imagettes, which depict the individual wave heights, are then mathematically transformed into averaged-out breakdowns of wave energy and direction, called ocean-wave spectra, which ESA makes available to scientists and weather centres.

Resources: European Space Agency -http://www.esa.int/esaCP/index.html

NASA

Landsat Satellite Mission Planned by USGS and NASA

Friday, May 18th, 2007

Scientists and engineers from the Department of the Interior’s U.S. Geological Survey (USGS) and NASA are moving forward in planning a successor to the Landsat 7 satellite mission which was successfully launched from Vandenburg Air Force Base on April 15, 1999. With the Landsat Data Continuity Mission (LDCM) satellite expected to launch 2011, the two agencies have announced their roles and responsibilities in mission development, subsystems procurement, and on-orbit operations.

Landsat 7 Satellite

Landsat 7 Satellite

To view new mission details click link below;

http://ldcm.usgs.gov/LDCMHome.php

LANDSAT image data has been used by government, commercial, industrial, civilian and educational communities throughout the world. The data is used to support a wide range of applications in such areas as global change research, agriculture, forestry, geology, resource management, geography, mapping, hydrology and oceanography. The images can be used to map anthropogenic and natural changes on the Earth over periods of several months to two decades. The type of changes that can be identified include agricultural development, deforestation, desertification, natural disasters, urbanization and the development and degradation of water resources. These changes, in turn, influence management and policy decision making.

Satellite image data enable direct observation of the land surface at repetitive intervals and therefore allow mapping of the extent and monitoring and assessment of:

LANDSAT 7 Image of Land Cover and Change Detection;

Agriculture Development

Parana, Brazil

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Satellite Image Data to Monitor Global Warming

Friday, May 11th, 2007

“Global change”, “Greenhouse effect”, “Global warming”. The media are full of statements, concerns, guesses, and speculation about these phenomena, as scientists and policy makers around the world struggle to address recent scientific observations that indicate human activities impact our environment.

ASTER Bhutan-Himalaya

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ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) instrument aboard NASA Terra satellite shows the termini of the glaciers in the Bhutan-Himalaya. Glacial lakes have been rapidly forming on the surface of the debris-covered glaciers in this region during the last few decades.
According to Jeffrey Kargel, a USGS scientist, glaciers in the Himalaya are wasting at alarming and accelerating rates, as indicated by comparisons of satellite and historic data, and as shown by the widespread, rapid growth of lakes on the glacier surfaces. According to a 2001 report by the Intergovernmental Panel on Climate Change, scientists estimate that surface temperatures could rise by 1.4deg Celsius to 5.8deg Celsius by the end of the century. The researchers have found a strong correlation between increasing temperatures and glacier retreat. Credit: Image provided by Jeffrey Kargel, USGS/NASA JPL/AGU.
Over the last century the average temperature has climbed about 1 degree Fahrenheit (0.6 of a degree Celsius) around the world.

The spring ice thaw in the Northern Hemisphere occurs 9 days earlier than it did 150 years ago, and the fall freeze now typically starts 10 days later.

The Arctic Climate Impact Assessment (ACIA) report recently concluded that in Alaska, western Canada, and eastern Russia, average temperatures have increased as much as 4 to 7 degrees Fahrenheit (3 to 4 degrees Celsius) in the past 50 years. The rise is nearly twice the global average. The United Nations’ Intergovernmental Panel on Climate Change (IPCC) projects that global temperatures will rise an additional 3 to10 degrees Fahrenheit (1.6 to 5.5 degrees Celsius) by century’s end.

View an animated video of the cryosphere of Greenland and Canada:

http://www.esa.int/esaEO/SEMRLH12Z0F_planet_0.html

Satellite remote sensing is an evolving technology with the potential for contributing to studies of the human dimensions of global environmental change by making globally comprehensive evaluations of many human actions from multispectral satellite images from satellite sensors such as Landsat(15m) and ASTER(15m) . Satellite sensor data have proven to be useful to the atmospheric and ocean sciences communities. The land sciences community has made extensive use of satellite image data for mapping land cover, estimating geophysical and biophysical characteristics of terrain features, and monitoring changes in land cover. More recently, the scientific community has witnessed a growing demand for high resolution satellite imagery on investigating the human dimensions of global change from sensors such as QuickBird(0.6m) and IKONOS(0.8m) resolution due to the quality and accuracy of detail of our ever changing planet.

Human actions involving biomass fuel consumption, land-use change, and agricultural activities all involve direct interaction with the global land surface. The extent of these interactions has prompted concern about the possible effects on the global physical, chemical, and biological systems. Large-scale changes in land use at rates unprecedented in human history are provoking considerable concern. Land-use change is frequently accompanied by alterations or changes in land cover, which may possibly contribute to subsequent environmental change. Evaluation of the static attributes of land cover (types, amount, and arrangement) and the dynamic attributes (types and rates of change) on satellite image data may allow the types of change to be regionalized and the proximate sources of change to be identified or inferred. This information, combined with results of case studies or surveys, can provide helpful input to informed evaluations of interactions among the various driving forces.

Beginning with the early use of aerial photography, remote sensing has been recognized as a valuable tool for viewing, analyzing, characterizing, and making decisions about our environment. In the past few decades, remote sensing technology has advanced on three fronts:

1) Predominantly military uses to a variety of environmental analysis applications that relate to land, ocean, and atmosphere issues.

2) Photographic systems to sensors that convert energy from many parts of the electromagnetic spectrum to electronic signals.

3) Aircraft to satellite platforms.

Today, we define satellite remote sensing as the use of satellite-borne sensors to observe, measure, and record the electromagnetic radiation reflected or emitted by the Earth and its environment for subsequent analysis and extraction of information.

Resources provided by:

http://rst.gsfc.nasa.gov/Sect16/Sect16_2.html

http://www.ciesin.columbia.edu/TG/RS/RS-home.html