Digital imagery can greatly enhance a GIS. Part of the raster data types, imagery is a powerful visual aid and serves as a source of derivative information such as planimetrics and classification schemes to derive such information as land use or vegetation. If your GIS covers a particularly large area, aerial imagery may not be a practical or economical choice. Satellite imagery is often the preferred choice of imagery for larger regions. More and more choices of satellite imagery are becoming available and the cost associated with its purchase is dropping.
Many of the satellite imagery can be purchased directly from the associated agencies. In addition, there are online sites that also specialize in satellite imagery sales. Plangraphics is a reseller of Space Imaging’s IKONOS imagery. EOMOnline sells several imagery such as Landsat 5, IRS Imagery and Landsat 7. Terraserver is also a well-known source of satellite imagery.
Satellite Imagery Terms
Useful for classifying material types on the Earth’s surface – beneficial in agriculture and forestry management, mineral exploration, environmental monitoring and national security activities.
Amount of time that passes before the satellite scans the same point of the globe.
Two or more images taken simultaneously, but each image taken in a different part of the electromagnetic spectrum.
Imagery taken of all wavelengths within the visible spectrum, though not uniformly.
The act of circling the earth. The type of orbit describes the path the satellite takes as it circles the earth.
The amount of ground covered in one pixel of the image. For example an image with one meter resolution means that each pixel in the image represents one square meter on the ground. Click here for examples of imagery at different resolutions.
An orbit that always passes over the earth at the same local sun time.
Amount of ground covered lengthwise in the passing of the satellite.
Flash Earth is an experimental application that loads in various imagery from some of the major online mapping applications. Created by Paul Neave, Flash Earth (as the name suggests) is a Flash-based viewing application for exploring the different satellite imagery available from Google Maps, Microsoft Virtual Earth, Yahoo! Maps, Ask.com, Open Layers and NASA Terra. While the functionality of this application is limited to a basic address search and the typical pan and zoom, it is useful for comparing the different aerial resolutions between these online mapping services.
Moderate-Resolution Satellite Imagery: USGS Open Report
The USGS has issued an Open Report that looks at the uses and users of Moderate-resolution imagery (MRI), particularly Landsat. The report is the result of a survey of U.S. based MRI by social scientists at the USGS Fort Collins Science Center. The study aimed to understand who the users are and what the benefits are of the use of MRI with a focus on Landsat use.
As defined by the report, MRI is imagery that meets four main criteria: covers a relatively large area of landmass (more than 60km), has a spatial resolution between 5 and 120 meters per image pixel, has repetitive coverage, and has measurements from several portions of the electromagnetic spectrum. The USGS supplies a significant amount of MRI through the operation of Landsat 5 and Landsat 7 satellites. Landsat imagery dating back to 1972 is made available through the Earth Resources Observation and Science (EROS) Center. Imagery is available with no user restriction or costs and, as a result, is a popular choice for MRI among users.
Over 2,500 users responded to the survey. Interestingly, more than half were not members of “any type of remote sensing or GIS organization and, during the snowball sampling, almost 35 percent indicated they did not know any other users of MRI.” The survey found that the average Landsat user was “male, white, 47 years old, and highly educated.” Additionally, “[t]hree-quarters of the users were male, more than 90 percent were white, more than 80 percent were between 30 and 59 years old, and two-thirds had masters degrees or above.”
The survey results further dissect what types of organizations use MRI and for what types of applications. There are several sections that break down the how the imagery is used, how that use has changed over time, and a look at the impact of having a no cost data policy.
Read the report:
The Users, Uses, and Value of Landsat and Other Moderate-Resolution Satellite Imagery in the United States—Executive Report (PDF) – U.S. Geological Survey Open-File Report 2011–1031, 42 p.
Authors: Holly M. Miller, Natalie R. Sexton, Lynne Koontz, John Loomis, Stephen R. Koontz, and Caroline Herman
2001 Inventory of Satellite imagery
Listed here are some of the most prominent sources of currently available satellite imagery and future satellite launches based on an inventory performed in 2001. This guide is meant to be a launching point for searching for and acquiring information about available satellite imagery. Individual choice of imagery will depends on many factors such as resolution, image type and cost.
|Launch Date:||24, September, 1999||Country:||USA|
|Intervals||2-4 Days||Resolution:||1 m panchromatic
4 m multispectral
1 m fused*
*one-meter fused panchromatic and multispectral resolution.
|Swath:||5 – 8 km||Orbit:|
|Intervals||~ 3 days||Resolution:||1 meter panchromatic
4 meter multispectral
8/20 meter hyperspectral
|Launch Date:||First Quarter 2001 (initially set for 1999)||Country:||USA|
|Intervals||~3 days||Resolution:||1 & 2 m panchromatic
4 m multispectral
|Launch Date:||August 1997||Country:|
|Intervals||Resolution:||1 km multispectral imagery
eight spectral bands, six in the visible and two in the near-infrared spectrum.
|Launch Date:||December 5, 2000 (initially set for late 1999)EROS A2 – 3rd quarter of year 2001||Country:||Israel|
|Agency:||ImageSat International(formerly West Indian Space)|
|Swath:||12.5 km||Orbit:||Polar, sun-synchronous|
|Satellite:||Imagery: EROS-B||EROS B Series|
|Launch Date:||EROS B1 – 2nd quarter of year 2002
EROS B2 – 4th quarter of year 2002
EROS B3 – 2nd quarter of year 2003
EROS B4 – 4th quarter of year 2003
EROS B5 – 2nd quarter of year 2004
EROS B6 – 4th quarter of year 2004
|Agency:||Israel Aircraft IndustriesCore Software Technologies|
|Satellite:||Advanced Land Observing Satellite (ALOS)||Imagery:||PRISM|
|Launch Date:||August 2002||Country:||Japan|
|Intervals||46 days||Resolution:||2.5 meters panchromatic|
|Agency:||Russian Space Agency (Sovinformsputnik)|
|Intervals||Resolution:||2-3 meters panchromatic|
|Satellite:||IRS-1C & IRS-1D||Imagery:||LISS|
|Agency:||Indian Space Agency|
|Intervals||5 days||Resolution:||5.8 meter panchromatic|
|Launch Date:||October 1994 – Resurs-01-3July 1998 –Resurs-01-4||Country:||Russia|
|Satellite:||Landsat 7||Imagery:||Enhanced Thematic Mapper Plus|
|Launch Date:||April 15, 1999||Country:||USA|
|Agency:||Originally NASA – USGS recently assumed responsibility.|
|Swath:||185 km||Orbit:||Near-polar, sun-synchronous|
|Intervals||16 days||Resolution:||30 meters 8-band multispectral
15 meters 1-band panchromatic
|Satellite:||Landsat 5||Imagery:||Thematic Mapper (TM)|
|Launch Date:||March 1, 1984||Country:|
|Swath:||185 km||Orbit:||Polar, sun-synchronous|
|Intervals||16 days||Resolution:||30 meters (except band 6 (thermal) – 120 meters)|
|Launch Date:||May 14, 1991||Country:||USA|
|Swath:||2399 km||Orbit:||Polar orbit, near circular|
|Intervals||14 times/dayWhere is it right now?||Resolution:||1.1 km|
|Launch Date:||Spot 1 – February 22, 1986
Spot 2 – January 22, 1990
Spot 3 – September 26, 1993
Spot 4 – March 24, 1998
Spot 5 – 2002
|Agency:||Spot||Coverage:||87° N to 87° S (lat.)|
|Swath:||900 km||Orbit:||polar, circular, sun-synchronous|
|Agency:||Canadian Space Agency (CSA) and MacDonald Dettwiler|
|Swath:||20, 100 and 500 km||Orbit:||sun-synchronous circular orbit|
|Intervals||3 days||Resolution:||2, 28 and 300 meters
high-resolution multi-polarized imagery