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A Guide to the Practical Use of Aerial Color-infrared Photography in Agriculture

Donald C. Rundquist and Scott A. Samson

Educational Circular 8

Conservation and Survey Division Institute of Agriculture and Natural Resources University of Nebraska-Lincoln


Introduction

The use of aerial photography in agriculture might eventually be considered as important a management tool as any other farm tool. Obtaining a general view of cropland from aloft by aerial photography could possibly mean the difference between a successful harvest or a preventable crop failure.

Aerial photography has been used widely in the United States since the 1930s to assist land managers in the evaluation of agricultural resources. Determining the amount of land planted to specific crops has historically been an important activity of the U.S. Department of Agriculture, and aerial photography has long provided that agency with a cost-effective and timely means of obtaining such data.

In Nebraska, aerial photography also has been flown on a regular basis for about fifty years. Extensive collections of historical photographs are held by agencies such as the Conservation and Survey Division at the University of Nebraska-Lincoln and the USDA Agricultural Stabilization and Conservation Service and Soil Conservation Service.

Traditionally, black-and-white (or "panchromatic") aerial photography has been the most common information source. With this type of film, the various colors and patterns of the land surface are depicted as a series of gray tones ranging from white to black. Panchromatic film is still widely used for a multitude of agricultural applications despite the fact that, in some cases, it is difficult to distinguish between different types of vegetation.

Infrared film, available in both black-and-white and color formats, is a relatively recent development. Color-infrared (CIR) film, sometimes referred to as "false-color," is the most common form. It was originally developed by the military for detection of camouflage, a concept based on the ability to distinguish between real vegetation and surfaces that have been merely painted green or covered with freshly cut brush or green netting. With color-infrared photography, painted surfaces and dead or dying vegetation were easily discriminated from live, healthy vegetation, and it was not long before the many agricultural applications of CIR technology became apparent to the civilian community.

In fact, numerous private companies, some operating in Nebraska, have now evolved for the sole purpose of providing low-level aerial infrared photographic services to farmers. However, despite the significant interest in the film today, it seems that many misconceptions persist. A basic understanding of the film's capabilities and limitations should enhance the applications of color-infrared film to general agricultural problems, even for the casual user.

This brief report represents an attempt to provide both potential and current users of infrared film with a concise, relatively non-technical reference on the physical properties and practical applications of CIR aerial photography as it relates to agricultural management. The work treats only color-infrared film because the farming public seems most interested in this particular type of film.