Practical Paper
The Nebraska Center-Pivot Inventory: An
Example of Operational Satellite Remote
Sensing on a Long-Term Basis
Donald C. Rundquist
Center for Advanced Land Management Information Technologies, Conservation and Survey Division, Institute of Agriculture
and Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68588-0517
Richard o. Hoffman
Department of Industrial and Management Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0518
Marvin P. Carlson
Conservation and Survey Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, Lincoln,
NE 68588-0517
Allen E. Cook
Center for Advanced Land Management Information Technologies, Conservation and Survey Division, Institute of Agriculture
and Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68588-0517
ABSTRACT: The objective of this paper is to summarize the history, procedures, and results of a long-term program of
inventorying center-pivot irrigation systems in Nebraska. Data concerning the location of pivots have been collected
each year from 1972 to the present, and summarized annually as a map publication. Inventory procedures are simplistic,
consisting of identifying and mapping occurrences of the characteristically circular pivot systems as interpreted from
photographic enlargements of Landsat imagery. A total of 2,665 pivots were recorded in 1972, and the cumulative total
for 1986 was 26,208; nearly a ten-fold increase over 14 years. The temporal periods of greatest increase coincide, as one
would expect, with generally dry conditions in the state. While the method for remote detection of irrigation systems
is ordinary, we believe that the Nebraska center-pivot inventory provides an excellent example of the practical utility
of remote sensing.
INTRODUCTION
Landsat-l in 1972 led to a multitude of attempted applications of satellite remote sensing in both agricultural and non-agricultural disciplines. In the former case,
researchers addressed problems such as rangeland monitoring
(e.g., Rouse et aI., 1974), soil classification (e.g., Parks and Bodenheimer, 1973; Lewis et aI., 1975), cropland classification/agriculturalland use (e.g., Hoffman et aI., 1976; Richardson et aI.,
1977; Westin and Lemme, 1978; Bauer et aI., 1978; Keene and
Conley, 1980), diseased crops (e.g., Gausman et aI., 1975), and
others (Rundquist and Samson, 1982).
One area of research, within the broad context of agricultural
applications of satellite remote sensing, which has attracted a
considerable amount of attention is that of identifying irrigated
cropland (e.g., Draeger, 1976; Heller and Johnson, 1979; Thelin
et aI., 1979; Thiruvengadachari, 1981; Kolm and Case, 1984). Of
course, an important motive for and implication of such work
is the concept of predicting levels of both energy use and water
consumption for agricultural production (e.g., Hoffman et aI.,
1974; Estes et aI., 1978; Thelin and Heimes, 1987). Landsat MSS
data have been utilized for this purpose, but the spectral separation of irrigated and non-irrigated crops can be very difficult.
Researchers have analyzed the spectral data in concert with
ancillary information such as "crop calendars" (Martinko, 1981),
meteorological data (Erb, 1979), and water-requirement information (Loveland and Johnson, 1983).
However, one particular type of irrigation system, the"center
pivot," can be identified on Landsat imagery with relative ease.
This is due both to its distinctive shape and the vegetative biomass under irrigation, as compared to surrounding non-irri-
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HE LAUNCH OF
PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING,
Vol. 55, No.5, May 1989, pp. 587-590.
gated vegetative cover (Hoffman, 1979; Buckwalter and Seevers,
1980) (Figure 1). Center pivots are based, in concept, on a water
well located in the center of an area (usually one-quarter section, or 64.75 hectares) with a linear system of pipes and sprinklers carried on large wheels in a circle around the well (Splinter,
1976; McKnight, 1979). This irrigation innovation has become
widely employed in the United States, especially within the
states of Nebraska, Texas, California, Kansas, and others. Center-pivot systems consume great quantities of both water and
energy; an estimated 496 litres of diesel fuel (or the equivalent)
per hectare-year and over 3,806,511 litres of water per hectareyear (Pape, 1976). Despite having had both a profound impact
upon the rural landscape and having been installed in large
numbers over broad geographic areas, only the state of Nebraska has consistently employed satellite remote sensing to
monitor the diffusion of this innovation over both geographic
space and a relatively long period of time.
BACKGROUND
The program of center-pivot monitoring in Nebraska dates to
1973, when it was proposed under the NASA University Affairs
Program. The statewide survey received support from the NASA
program until 1985, when it was placed (as fully operational)
within the Water-Use Program of the Conservation and Survey
Division, University of Nebraska. Several principal investigators and numerous students have been involved in the project
since its inception in the early 1970s.
PROCEDURES
The methods and procedures have varied somewhat over the
years due to changes in the Landsat technology itself, the var0099-1112/89/5505-587$02.25/0
©1989 American Society for Photogrammetry
and Remote Sensing
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PHOTOCRAMMETRIC ENGINEERI C & REMOTE SE SI G,1989
annual survey since its inception. The database lists each pivot
located in the state by its U.S. Geological Survey state designation number (31 for Nebraska), the county number (numbered sequentially in alphabetical order, 1 to 93), the pivot location
to the nearest y. of Y. section (PLS), the years in which the pivot
was observed, and the Natural Resources District (NRD) in which
the pivot is located. Nebraska is divided into 24 NRDs according
to watershed boundaries.
Landsat Thematic Mapper (TM) images were first used as the
data source for center-pivot inventory in 1985, although the
methods described above have remained virtually unchanged.
The improved spatial resolution of the TM has proven very important in the discrimination of the circular irrigation systems,
and it seems plausible that the overall accuracy of the project
is increased now that the survey is based on TM data. However,
the recent EOSAT decision to no longer provide black-and-white
TM image products to users may threaten, or at least complicate,
procedures regarding future Nebraska center-pivot inventories
(Severson, personal communication, 1988).
RESULTS AND DISCUSSION
FIG. 1. A portion of a Landsat TM Band-3 image (28 July 1987, Scene ID
5124416432) showing center-pivot irrigation systems near Atkinson, Nebraska. The Niobrara River flows east-west at the top of the image. Black
circles are center pivots with healthy, vigorous crops. (Scale approx.
1:364,320.)
iable skill levels of image analysts, and the terminology used to
describe findings summarized on published maps. The basic
methodology consists of identifying and mapping the occurrences of the characteristic circular features as interpreted from
enlargements of Landsat imagery.
The annual inventory of center-pivot systems undertaken for
the years 1972 through 1984 were accomplished using LandsatMSS photographic products. Imagery was obtained in negative
form (1:1,000,000 scale) for the red band (0.63 to 0.69 !J.m). Images were selected each year in the late July-early August time
period with 10 percent or less cloud cover. The negative images
were enlarged and printed on photographic paper at 1:250,000
scale. They were then compatible in scale with existing county
maps which depict roads, rivers, and the Public Land Survey
(PLS) system grid.
The first step was to produce a composite computer plot, on
a per-county basis, of the center pivots mapped for all previous
years. The plot, output on transparent acetate, was used as an
overlay to the Landsat-MSS imagery. Pivots interpreted on the
current-year imagery but not on the previous-year plot were
annotated to the transparency as newly observed systems. Similarly, pivot locations interpreted on the cumulative plot that
were not seen on the current-year imagery were noted as being
not observable for that particular year (and were, most likely,
idle). The transparencies were then overlaid on the county maps
to obtain pivot-location descriptions (PLS) for the newly observed entries.
A computerized database has been an important part of the
After the data were collected for a given year and each centerpivot system was given a locational reference (PLS), a map was
generated (Figure 2). These final products, which are multicolored, were distributed to a variety of users throughout Nebraska, and have generated considerable interest. The current
method of mapping involves identifying the newly observed
and previously observed pivots with separate colors. Associated
with each annual map is a county-by-county tabular summary
of pivot occurrence. It is from evaluations of these statistical
data for each year that some inferences can be drawn about
general statewide trends over time.
For the most part, the general trend associated with centerpivot systems in Nebraska has been one of increasing use (Figure 3). A total of 2,665 pivots was recorded in 1972, and the
cumulative total for 1986 was 26,208; nearly a ten-fold increase
over 14 years. The temporal periods of greatest increase coincide, as one might expect, with generally dry conditions in the
state; e.g., the period 1974 to 1976 (compare Figures 4 and 5).
In 1976, near the end of a particularly dry period, over 3,000
"new" pivots were observed on the satellite imagery (i.e., seen
for the first time). The annual growth of the pivot phenomenon
has diminished somewhat in the 1980s, as compared to the
previous decade (Figure 4).
The long-term project involving monitoring center-pivot development in Nebraska is considered both successful and useful
for at least three reasons. First, it provides a relatively inexpensive method for simple record-keeping of pivot numbers on a
year-by-year basis. Second, the annual multi-colored maps have
achieved considerable importance in the state because they provide a historical, graphic measure of the spatial diffusion of this
irrigation innovation. Third, the resulting georeferenced digital
dataset holds considerable potential for investigating the centerpivot phenomenon within the context of a Geographic Information System (GIS), that is, in relation to other layers of spatial
information such as soils, topography, land-ownership patterns, and ground-water levels (Murray, 1986). While the method
for remote detection of irrigation systems is extremely simplistic, we believe that the Nebraska center-pivot inventory provides an excellent example of the practical utility of remote
sensing.
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THE NEBRASKA CENTER-PIVOT INVENTORY
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FIG. 2. Location of center-pivot irrigation systems in Nebraska as of 31 December 1986. Each dot represents one center-pivot irrigation system.
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FIG. 3. Cumulative total center pivots observed in Nebraska (1972-1986).
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30
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PHOTOGRAMMETRIC E GINEERING & REMOTE SENSING, 1989
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(Received 14 September 1988; accepted 4 November 1988; revised 27
December 1988)
International Training Program in Remote Sensing
"Image Processing of Satellite Data for Natural Resource Applications"
5·30 June 1989
Albuquerque, New Mexico
The Technology Application Center (TAC) of the University of New Mexico is offering a summer international training program in
remote sensing, "Image Processing of Satellite Data for Natural Resource Applications", from 5-30 June 1989. This course is intended
for resource managers and technicians in all natural resource fields, including agriculture, geology, hydrology, soil science, forestry,
and land use planning. It is designed for individuals who already have a fundamental understanding of satellite remote sensing and
who need to develop a practical working knowledge of digital image processing and analytical techniques. [An optional one-week intensive introduction to remote sensing will be provided immediately prior to the course from 29 May-2 June, for an additional $650.]
The four-week course will emphasize a computer image processing system. Enrollment will be limited to ten participants to ensure
maximum hands-on experience. The fee is $2350, which includes instruction costs, training materials and workbook, and a limited
number of field trips. International traveling costs and living expenses are to be met by sponsoring agencies. Normal USAID or
UN/FAO per diem rates are adequate to cover local living expenses. Applications should be received by 1 May.
TAC also offers "The Visiting Scientist Program" designed for long-term training or technical asssistance in remote sensing and/or
access to advanced image processing facilities to carry out remote sensing projects. It provides an ideal format for trainees sponsored
by international development organizations. For more information contact:
Dr. Dario Rodriguez-Bejarano
Technology Application Center
University of New Mexico
Albuquerque, NM 87131
Telephone 505-277-3622
telex 660461 ASBKS UNM ABQ
Fax 505-277-3614