Cheyenne Bottoms -- Ikonos imagery

Ikonos Imagery
Cheyenne Bottoms, Kansas
James S. Aber & Firooza Pavri

Table of Contents
2003 image Panchromatic
Natural color False color
2004 image NDVI image

**Table of Contents**
2003 image	Panchromatic
Natural color	False color
2004 image	NDVI image

2003 image

The Ikonos satellite provides high-resolution imagery in visible and near-infrared portions of the spectrum as indicated in the table below. The commercial satellite was launched in 1999 and acquires imagery as requested by customers for specific locations and conditions. In our case, we ordered an image scene covering 10 km by 10 km (100 km²) centered on the Nature Conservancy portion of Cheyenne Bottoms. We requested a cloud-free image for June 2003. Attempts to acquire a cloud-free image in June were unsuccessful, so we extended the effort into early July. A cloud-free image was acquired on July 11, 2003.

**Ikonos bands and resolution**
Color band	Resolution
Blue visible	4 meters
Green visible	4 meters
Red visible	4 meters
Near-infrared	4 meters
Panchromatic*	1 meter

* Pan = green + red + near-infrared.

In early July, most of the shallow marshy zones had dried up, following early spring flooding. Residual pools of water occupied the deepest basins within the Nature Conservancy marshes. Extensive bare mud flats existed along with large areas of cattail beds that had died during the drought of the previous year.

Panchromatic imagery

Given its 1-meter resolution, the pan band rivals conventional airphotos for detailed imagery. The whole scene was collected at the same time under uniform lighting and ground-cover conditions, and thus is quite superior to patching together multiple airphotos to achieve the same areal coverage. Compare, for example, the following Ikonos images with the DOQ mosaic, which contains confusing differences in the appearances of water bodies.

Whole Ikonos scene, panchromatic band. The Nature Conservancy land occupies the center of the scene. Hoisington appears in the upper left corner, and part of the state wildlife area is visible in lower right corner. Scene acquisition date 11 July, 2003. Click on small image to see larger version.
Detailed image of Nature Conservancy land at Cheyenne Bottoms. The delta of Blood Creek covers the south-central portion and Deception Creek has built a smaller delta in the north-central part of the scene. Between the two is a low-lying, marshy region divided into an upper part, known as Clearwater pool, and a lower portion. Small water bodies occupy deeper basins within Clearwater pool, but the lower marsh has no standing water.
Closeup image of the Clearwater pool and lower marsh area. Artificial drainage channels: A - drain from Clearwater pool to the lower marsh, B - drain from lower marsh. Mottled zones within marshes are cattail beds (C).
Closest view of Clearwater pool, Deception Creek and its delta. Sites A and B are ground locations for SFAP. This level of magnification and detail is not possible with the other multispectral bands. Note cattle trails within the cattail beds and across the mud flats.

Natural-color composite

The primary color (blue, green, red) bands may be combined in a natural-color composite. While this composite is based on visible colors, it does not appear exactly as the human eye would perceive the scene. Active vegetation appears in dark green/olive colors, rather than the bright green and yellow green seen by people on the ground. More apparent on this composite is the reddish brown color of fallow or harvested fields. Bare mud flats appear in gray: dark gray for moist surface and light gray for dry surface. Water bodies (pools and streams) are black.

Whole scene, natural-color (blue, green, red) composite. Scene acquisition date 11 July, 2003. Click on small image to see larger version.
Detailed image of Nature Conservancy land at Cheyenne Bottoms.
Closeup image of the Clearwater pool and lower marsh area.

False-color composite

The false-color composite is based on green, near-infrared, and red bands color coded respectively at blue, green, and red. The near-infrared band is particularly sensitive to photosynthetically active vegetation, which in this composite appears as bright green. Fallow or harvested fields are depicted in pale red to reddish purple colors. Bare mud flats are purple: dark purple for moist surface and light purple for dry surface. Water bodies (pools and streams) are black. This composite is especially useful for distinguishing active vegetation, mud flats, and water bodies.

Whole scene, false-color (green, nir, red) composite. Scene acquisition date 11 July, 2003. Click on small image to see larger version.
Detailed image of Nature Conservancy land at Cheyenne Bottoms.
Closeup image of the Clearwater pool and lower marsh area.

2004 image

A second Ikonos image dataset was acquired on May 24, 2004. This dataset represents the culmination of a drought in which surface water bodies dried up in the study area. Vegetation was much diminished and most cattail beds died. The following natural-color composite images contrast markedly with those from the summer of 2003.

Natural-color composite based on blue, green and red spectral bands. Overview of northwestern portion of Cheyenne Bottoms region, near Hoisington, Kansas. Compare with images above.
Stream channels and marsh pools have no surface water. Light gray indicates dry mud flats, blue-gray shows moist mud flats, and dark gray is dry meadow. Maroon and reddish brown are harvested and fallow fields, olive and dark green represent active vegetation. This image represents the culmination of drought conditions.

NDVI image

In order to evaluate subtle variations in vegetation and soil moisture, a special false-color composite was created based on the normalized difference vegetation index (NDVI). This composite includes the blue band, NDVI, and green band respectively color coded as blue, green and red. In this composition, active vegetation appears in green and yellow-green shades. Bare ground, fallow fields, and other non-vegetated surfaces are depicted in purple and maroon colors.

Whole scene NDVI composite image. Active vegetation is restricted mostly to a few agricultural fields and parts of the state wildlife area (lower right corner).

Detailed view of Nature Conservancy land in northwestern portion of Cheyenne Bottoms. Compare with false-color composite images above.

	Whole Ikonos scene, panchromatic band. The Nature Conservancy land occupies the center of the scene. Hoisington appears in the upper left corner, and part of the state wildlife area is visible in lower right corner. Scene acquisition date 11 July, 2003. Click on small image to see larger version.
	Detailed image of Nature Conservancy land at Cheyenne Bottoms. The delta of Blood Creek covers the south-central portion and Deception Creek has built a smaller delta in the north-central part of the scene. Between the two is a low-lying, marshy region divided into an upper part, known as Clearwater pool, and a lower portion. Small water bodies occupy deeper basins within Clearwater pool, but the lower marsh has no standing water.
	Closeup image of the Clearwater pool and lower marsh area. Artificial drainage channels: A - drain from Clearwater pool to the lower marsh, B - drain from lower marsh. Mottled zones within marshes are cattail beds (C).
	Closest view of Clearwater pool, Deception Creek and its delta. Sites A and B are ground locations for SFAP. This level of magnification and detail is not possible with the other multispectral bands. Note cattle trails within the cattail beds and across the mud flats.

	Natural-color composite based on blue, green and red spectral bands. Overview of northwestern portion of Cheyenne Bottoms region, near Hoisington, Kansas. Compare with images above.
	Stream channels and marsh pools have no surface water. Light gray indicates dry mud flats, blue-gray shows moist mud flats, and dark gray is dry meadow. Maroon and reddish brown are harvested and fallow fields, olive and dark green represent active vegetation. This image represents the culmination of drought conditions.