Mapping is one of the first phases of operations in any eradication
zone. The purpose of mapping is to identify the exact location of each
cotton field as well as its surrounding environment.
Each cotton field in the state is identified with a unique number as
indicated in the following description: The cotton production area in
the state of Texas is divided into 16 zones. Each zone is divided into
work units of about 15,000-18,000 acres of cotton. Each work unit has
a unique three-digit number.
The first number refers to the zone number, while the other two refer
to each work unit within the zone, using an arbitrary series of
numbers beginning with 01. A work unit has several townships,
36-square-mile areas that are divided into sections, which measure 1
The sections are numbered in a zig-zag manner, east to west. The first
section, No. 1, would be the northeast corner of the township, and the
last section, No.36, would be the southeast corner of the township.
All fields within each section are identified and assigned a unique
four-digit number. The first two digits refer to the section number
and the second two digits refer to a series of numbers within each
section beginning with 01. This numbering system results in a unique
number for each cotton field throughout the state.
Global Positioning System aids eradication
The Global Positioning System is based on a system of satellites
developed by the U.S. Department of Defense. Now fully operational,
the system has 24 satellites orbiting the earth at an altitude of
The eradication program uses hand-held GPS receivers to map fields.
By measuring the travel time of signals transmitted from each
satellite, the receiver computes its distance from that satellite.
With distance measurements from at least three satellites, a
hand-held receiver can calculate its current location. GPS works
anywhere on earth, 24 hours a day, in any weather. (More
information on how GPS works. Use the back button on your
browser to return to this page.)
When mapping a cotton field, the program worker takes GPS satellite
readings at points around each field. The hand-held unit stores
these readings until the worker returns to the office. Back at the
office, the worker downloads the readings from the GPS unit into a
Using the collected data, the computer draws an exact map of the
cotton field. This map shows the length and width of the field,
where it is located and the exact number of acres within that field.
These field maps are stored in the computer and are used for
trapping, insecticide applications and other program activities.
Cotton producers can assist with mapping by knowing who their field
unit supervisors are and guiding them to any cotton fields on their
farms. The more accurately fields are mapped, the more accurately
they will be treated during program activity.
The USDA's Farm Services Agency office also plays an important part
in mapping fields. The FSA, through its cotton-acreage certification
program, has information about previously planted cotton acreage in
each zone, work unit, township and section.
Supervisors combine the FSA information, such as farm number and
name, with the program’s GPS mapping to produce a detailed map of
all cotton fields in their units.