APU's have been developed for Russia, Canada, and the Great Plains 
of the United States and are currently being constructed for other 
countries. For illustrational purposes, this paper will discuss 
the APU's developed for the Great Plains of the United States.* 
The purpose of this paper is to define and illustrate the value of 
an APU concept in the exploitation of multispectral scanner (MSS) 
data. Additionally, it will show the versatility and applicability 
to data processing and analysis techniques. 
II. Development and Evaluation of Agrophysical Units 
A. Development 
Agrophysical units were derived from interpreting and synthesizing 
Landsat imagery, soil maps, and meteorological data. The base map 
for constructing these units was the Operational Navigation Chart 
(ONC) at a 1:1,000,000 scale. All overlay constructions were made 
on transparent acetate registered to the ONC base map. 
Figure 1 is a flow diagram showing the inputs and procedures for 
developing APU's. Landsat full frame, color infrared, imagery of the 
Great Plains (1:1,000,000 scale) were used to identify agricultural 
boundaries discerned by field patterns. These boundaries were 
delineated on an overlay. 
Soil information was derived from Aandahls Soil Map of the Great 
Plains! and available state and county soil reports. An overlay 
was developed showing the suitability of the soils for growing wheat. 
For example, a one indicated that the soil had excellent potential 
for wheat. A soil having a rating of four was poorly suited for 
wheat. Criteria used to rate the Great Plains soils were determined 
from the following soil characteristics: texture, depth, water- 
holding capacity, drainage, salinity, and slope. Details on soil 
suitability ratings are discussed by J. Downs? and F. Westin. 
Climatic data were used to set precipitation and temperature varia- 
tions within an APU. Weather stations with at least ten consecutive 
years of meteorological data were plotted. The mean growing season 
temperature and annual precipitation were printed next to each sta- 
tion location. Isolines were drawn using a contour interval of 50 
mm precipitation and 1°C for temperature. 
Preliminary APU's were developed by delineating similar soils and 
agricultural densities from the superimposed soils and agriculture/ 
nonagriculture overlays. These units were then checked against the 
*For LACIE purposes, the Great Plains constitutes the following 
states: Texas, Oklahoma, Kansas, Nebraska, Colorado, South Dakota, 
North Dakota, Montana, and Minnesota.