Earthshots is an ebook of before-and-after Landsat images (1972-present), showing recent environmental events and introducing remote sensing. Earthshots comes from the U.S. Geological Survey's Center for Earth Resources Observation and Science (EROS), Sioux Falls S.D., the world's largest archive of earth science data and the official National Satellite Land Remote Sensing Data Archive.

In the article below (read first):

• Reading Earthshots
• What the colors mean
• Garden City irrigation

• Remote sensing before Landsat 1
• The Landsat Project
• How images represent Landsat data
• Beyond looking at pictures
• Map legends
• E-mail EROS Customer Services
• About Earthshots

The image on the left shows Garden City, Kansas in 1972. To see the same area 16 years later, click on the "1988" in the caption below the image. Try switching between 1972 and 1988. Try the map. Try zooming in (click inside the yellow brackets) and zooming out (click outside/without the yellow brackets).

Many images and icons have pop-up messages if you point to them. You can also watch your browser's status bar for tips. The navigation help image summarizes where to click:

Zoom in/out: click inside/outside the brackets

Photograph: camera icon

Table of contents: world or "shutter world" icons

E-mail EROS Customer Services: mailbox

Help articles: question mark

Footnotes: ¹ little numbers

As this chart shows, Landsat images show how much energy from the sun (electromagnetic radiation) was reflecting off the Earth's surface when the image was taken. Clear water reflects little radiation, so it looks black. Pavement and bare ground reflect a lot of radiation, so they look bright. Urban areas usually look light blue-gray. Vegetation absorbs visible light but reflects infrared, so it looks red. This is a customary way to show satellite images.

(Some images have black "zero fill" at the corners, because the Landsats do not fly straight north-south. Most images are color-adjusted and reduced-resolution.)

For more details, read the help article on EMR represented by RGB.

Garden City irrigation

These Landsat MSS images center on Finney County, in southwestern Kansas. Garden City is centered in the brackets, with Lake McKinney west of town, and the Arkansas River just south of town flowing eastward. From 1972 to 1990 Garden City's population grew from about 15,000 to about 24,000.¹

Much of the former shortgrass prairie of western Kansas is now irrigated cropland. Common crops in this area are corn, wheat and sorghum. Red areas in the images are healthy vegetation. Light-colored cultivated fields in the images are fallow or recently harvested wheat fields.

These images show center-pivot irrigation systems (the small circles) multiplying between 1972 and 1988. From 1969 to 1987, irrigated acreage in Kansas increased by 62%, from 1.5 million acres to 2.4 million acres. In only the years 1984-1988, Kansas farms with center-pivot irrigation systems increased 19%, from 2,630 farms to 3,122 farms. As of 1987, Finney County led the state in irrigated acreage, with 184,177 acres.²

This area utilizes irrigation water from the Ogallala Aquifer, which underlies an area from Wyoming to Texas. Landsat images are useful for measuring irrigated crop acreage, a key component of modeling aquifer response to changes in water use.

Thanks for reading this article. Now click on the world map below the image (it looks like this: ) to read some other articles. From anywhere in Earthshots you can come back here by clicking on a red question mark ().

Footnotes

1. The population figures are estimated from these data for the town of Garden City: Merriam Webster's New Geographical Dictionary, 1980: 1970c est. 14,790. Encyclopedia Britannica, 15th edition, 1988: 1982 est. 20,082. U.S. Census: 1990 24,097.

2. Rajinder S. Bajwa and others, 1992, Agricultural irrigation and water use: Washington, D.C., USDA Economic Research Service, Agriculture information bulletin no. 638.

Other references

Billard, Jules B., and Blair, James, P., 1970, The revolution in American agriculture: National Geographic Magazine, vol. 137, no. 2, February, p. 147-185.

The Exploratorium. Electromagnetic Spectrum (San Francisco: The Exploratorium, 1991), 85 x 61 cm color chart.

N. M. Short, P. D. Lowman Jr., S. C. Freden and W. A. Finch Jr. Mission to Earth: Landsat Views the World Washington, D.C.: National Aeronautics and Space Administration, NASA SP-360, 1976) 459 pp.

Linda Spizzirri, ed. An Educational Coloring Book of Satellites (Medinah, Illinois: Spizzirri Publishing Co., Inc., 1986), 30 pp.

Thelin, Gail P. and Heimes, Frederick J., 1987, Mapping irrigated cropland from Landsat data for determination of water use from the High Plains Aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological Survey Professional Paper 1400-C.

U. S. Geological Survey. Historical Landsat data comparisons; illustrations of the Earth's changing surface (1995) 45 p.

U. S. Geological Survey. Landsat Data Users Handbook (1979) 207 pp.

U. S. Geological Survey, and National Oceanic and Atmospheric Administration. Landsat 4 Data Users Handbook (1984) 244 pp.

Zwingle, Erla, and Richardson, Jim, 1993, Ogallala aquifer: wellspring of the high plains: National Geographic Magazine, vol. 183, no. 3, March, p. 80-109.

Satellite images

LM1032034007222990 (Landsat 1 MSS, 16 August 1972)

LM5030034008822890 (Landsat 5 MSS, 15 August 1988)

The world mosaic used in Earthshots was compiled at EROS from AVHRR scenes acquired 21-30 June 1992 by the NOAA 11 satellite. The band combination is AVHRR 2 1 1, to approximate the band combination MSS 4 2 1. Antarctica was added to the image later as a plain white mask.

Special Projects Image

A comparison image of the 16 August 1972 and 15 August 1988 Garden City images is available as Special Projects Image E-1847-810CT from USGS EROS Customer Services.

Maps

U.S. Geological Survey, 1984 (compiled in 1961, edition of 1984), State of Kansas: scale 1:500,000.

Mosaicked maps: U.S. Geological Survey, 1975 (1955, revised 1975), Scott City, Kansas: scale 1:250,000. U.S. Geological Survey, 1975 (1955, revised 1975), Dodge City, Kansas: scale 1:250,000.

The maps in Earthshots labeled "commercial maps" are from Digital Wisdom Inc., 1995, Mountain High Maps: Tappahannock, Va., Digital Wisdom. Copyright 1995 Digital Wisdom Inc. (The use of any trade, product, or firm name in this work is for descriptive purposes only and does not imply endorsement by the U.S. Government.)

Photographs

The photographs for this article were taken on 12 March 1998 by Robb Campbell, USGS, with Peter Devincentis, USGS.

This article was first released 14 February 1997, and last revised 14 August 2000.