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 square mile.
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 11,000 miles.
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.)
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 computer.
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