United States 

 Department of 

 Agriculture

 National

 Agricultural 

 Statistics 

 Service

 Research and 

 Development Division

 Washington DC 20250

 RDD Research Report 

 Number RDD-06-04

September 2006

 

Using Handheld Global 

Positioning System 

Receivers for the Wheat 

Objective Yield Survey 

Michael W. Gerling 

This paper was prepared for limited distribution to the research community outside the United States 

Department of Agriculture. The views expressed herein are not necessarily those of the National 

Agricultural Statistics Service or of the United States Department of Agriculture. 

i 

EXECUTIVE SUMMARY 

In 2005, Washington field enumerators successfully showed that handheld Global Positioning 

System (GPS) receivers could be utilized for the Agricultural Resource Management Survey 

Phase II and for the June Area Survey. Next, the Washington Field Office and the Research and 

Development Division investigated if GPS receivers could assist field enumerators with the 

Wheat Objective Yield Survey. 

Currently, Wheat Objective Yield Survey field enumerators go to specified areas of the sampled 

wheat fields, lay out two objective yield units and record various crop counts. Every month until 

the fields are harvested, the enumerator returns to the same units and records crop counts. 

Sometimes a field enumerator has difficulty finding the same location again or a different field 

enumerator may need to enumerate the field and is unable to find the same location. This costs 

NASS in field enumeration time, and in those instances where the units were unable to be found, 

the data quality suffers. 

In this study, 23 Washington field enumerators were provided with handheld GPS receivers to 

aid in the enumeration of 160 winter wheat samples. On their initial visit to each sampled field, 

they recorded the latitude and longitude coordinates of each unit as it was being laid out. Upon 

subsequent field visits, if an enumerator had difficulty finding the units, the enumerator would 

review the unit’s coordinates and find the unit of interest using the GPS receiver. Field 

enumerators were also asked to complete a feedback form for each sample. Of the 160 forms 

expected, 107 were completed and returned. 

Overall, the field enumerators had no problem using their GPS receivers in initially obtaining the 

units’ latitude and longitude coordinates. In four instances the GPS receivers were useful in 

locating the Wheat Objective Yield Survey units on subsequent visits. The other times the field 

enumerators were able to find their sample units with no problem. 

Costs Benefits 

$50 Equipment and supplies. 

$68 Enumerator training. 

1 hr. Statistician time in preparing and 

 training enumerators. 

GPS receivers were used four times in aiding 

the enumerator to locate units on subsequent 

visits. 

Re-use the GPS receivers over multiple years 

for the Wheat Objective Yield Survey, June 

Area Survey, and the Agricultural Resource 

Management Survey – Phase II. 

ii 

RECOMMENDATION 

1. Recommend field offices already having Global Positioning System (GPS) receivers use 

them for the Wheat Objective Yield Survey since, with minimal expense, there is 

potential to improve data quality and save enumeration time. However, do not 

recommend purchasing GPS receivers for additional field offices for the sole purpose of 

using them for the Wheat Objective Yield Survey since the savings were not measurable. 

1 

Using Handheld Global Positioning System Receivers for the 

Wheat Objective Yield Survey 

Michael W. Gerling1/

Abstract 

The National Agricultural Statistics Service (NASS) surveys United States and

Puerto Rico agriculture for the purpose of making estimates on crops, livestock, 

production practices, farm economics, etc. 

The Wheat Objective Yield Survey requires field enumerators to physically go to 

sampled wheat fields, lay out two objective yield units and record various crop

counts. Field enumerators return to the same locations every month and record 

various crop counts until the fields are harvested. Sometimes a field enumerator 

has difficulty or is unable to find the same location again. This costs NASS in 

field enumeration time, and in those instances where the units are unable to be 

found again, the data quality suffers. 

In 2005, NASS researched whether providing field enumerators with handheld 

Global Positioning System (GPS) receivers would be beneficial in finding the 

Wheat Objective Yield Survey units on subsequent field visits. 

KEY WORDS: Agricultural Surveys, Data Collection, GPS 

1. INTRODUCTION 

The National Agricultural 

Statistics Service’s (NASS) primary 

purpose is to provide timely, 

accurate and useful statistics on

United States and Puerto Rico

agriculture. NASS conducts 

hundreds of surveys for the purpose 

of making estimates on crops, 

livestock, production practices, farm 

economics, etc. 

The Wheat Objective Yield

Survey is the third survey to use 

___________________ 

1/ Michael W. Gerling is a Mathematical Statistician with the National Agricultural Statistics 

 Service - Research & Development Division, located at Room 305, 3251 Old Lee Highway, 

 Fairfax, VA 22030. A special thanks to the Washington State Field Office, Washington’s 

 Field Enumerators, Linda Simpson, Kay Turner and Dan Beckler for their dedication and 

 commitment in making this research project a success.
2 

handheld Global Positioning System (GPS) 

receivers for data collection. In 2004 GPS 

handheld receivers were successfully used 

for Washington Field Office’s Agricultural 

Resource Management Survey Phase II 

(ARMS II) and in 2005 were marginally 

successful for the June Area Survey. 

2. WHEAT OBJECTIVE YIELD 

SURVEY 

The Wheat Objective Yield Survey 

(WOY) is conducted annually in twelve 

states and provides information used to 

forecast the amount of wheat harvested per 

acre as well the amount of wheat unable to 

be harvested. Ultimately, the data provide an 

estimate for the production of wheat at the 

state, regional, and national levels. 

To obtain these data, field 

enumerators physically go to sampled wheat 

fields, lay out two objective yield units and 

record various crop counts. Field 

enumerators return to the same locations 

every month and record various crop counts 

until the fields are harvested. 

On the initial visit to the field, the 

enumerator ties red flagging ribbon at the 

point of entry into the field and around the 

outer-most plants of the rows where the 

units are located. The ribbon aid the 

enumerator in returning to the designated 

area the following month. At the end of 

each month from April through August, the 

enumerator returns to the same units and 

records the various crop counts. 

A wheat field may have up to four 

samples within it. Each sample consists of 

two units located within the field. Each unit 

is composed of an area which is 

approximately six feet in length and three 

crop rows wide. 

3. WHAT IS A GPS HANDHELD 

RECEIVER? 

The Global Positioning System is 

comprised of at least twenty-four satellites 

orbiting the earth. These satellites transmit 

signals to GPS receivers on the ground. The 

majority of GPS receivers are about the size 

of a standard television remote control. 

A GPS receiver only receives signals 

from the satellites. It does not transmit. To 

function properly, a GPS receiver requires 

an unobstructed view of the sky. 

First, the GPS receiver acquires 

signals from these various satellites. Next, 

the GPS receiver determines the location of 

the satellites from the information included 

in the satellites’ transmissions. The receiver 

then calculates the distance it is from each 

satellite. Finally, the receiver is able to 

determine where it is actually located on the 

Earth within a certain degree of accuracy. 

The receiver will display its location 

in latitude and longitude coordinates. 

Latitude measures the distance north or 

south from the Equator while longitude 

measures the distance east and west from the 

Prime Meridian. 

A common use of GPS receivers is 

for hiking. Hikers utilize these receivers to 

trace their trail or to mark a unique location 

that they would like to return to at a later 

date. 

The particular GPS receiver used in 

this study was the Garmin GPS-72. See 

Figure 1. The GPS receivers are the same 

receivers purchased and used for the ARMS 

II research project conducted in the fall of 

2004. At that time Garmin was selected 

because the company was a respected 

manufacturer of GPS receivers for fifteen 

years. The GPS-72 model was also among 

the lowest-price GPS receivers ($150) 
3 

offering Wide Area Augmentation System 

(WAAS). WAAS provides the potential to

obtain a level of accuracy of ten feet. 

Typically, the GPS-72 receiver will provide 

a level of accuracy between 10 and 50 feet. 

Figure 1: Garmin GPS-72 

4. THE RESEARCH PROJECT 

Washington’s 2005 WOY sample 

consisted of 160 winter wheat fields. 

In previous WOY data collections, 

field enumerators would sometimes have a 

difficult time locating their marked samples 

from their last visit. The reasons vary from 

the identifiable ribbon blowing away in the 

wind, to the enumerator being at the 

completely wrong field. In a few cases, the 

ribbon is accidentally cut when agricultural 

workers mow the grass along the edge of the 

field. At this point, the enumerator then has

to go to the field=s starting corner and count 

off the same number of rows and paces into 

the field, as on the initial visit, and

hopefully, find the sample units. However, 

there are times that a sample unit cannot be 

found, at which point the enumerator has to 

lay out the unit again, wasting valuable time 

and resources. This also breaks the data 

series that was being created for that 

particular field and thus the quality of the 

data suffers. 

Hence, the Washington Field Office

(WA FO) supplied their field enumerators 

with GPS receivers to assist in locating the 

sampled wheat fields’ units. 

The expectation was that equipping 

enumerators with low-cost handheld GPS 

receivers, the field enumerators would save 

time in those instances when they have

difficulty finding a unit or are unable to 

locate a unit and have to lay out a 

replacement unit. 

4.1 ENUMERATOR TRAINING 

Each year a Wheat Objective Yield 

Survey Workshop is conducted to review the 

details of the survey and data collection 

procedures. Educating all 23 field 

enumerators on how to use their GPS 

receivers was incorporated into the 

workshop for the 2005 survey. 

For the entire sample, Washington 

field enumerators were instructed to do the

following: During the initial visit, use the 

GPS receivers to determine the latitude and

longitude coordinates of both units. Record 

these coordinates on the outside of the

manila kit envelope (one envelope per 

sample was provided) and on the completed 

Part B Form which is completed at the initial 

visit. Mail the completed Part B Forms to 
4 

the office. Thus the WA FO could verify 

that the latitude and longitude coordinates 

were indeed obtained. This was also 

beneficial if a different field enumerator or 

office staff needed to visit the field and 

record counts. During subsequent visits, if 

the field enumerator was having difficulty 

finding the sample units, he/she would 

review the coordinates on the kit envelope 

and use the GPS receiver to guide him/her to 

the unit of interest. However, since the 

Garmin GPS-72 receiver’s level of accuracy 

is between 10 and 50 feet, the field 

enumerator would still have to look around 

for the sample unit. 

Finally, the field enumerators were 

to complete the Enumerator Feedback Form 

(similar to a diary) and record any problems 

in using the GPS receivers in determining 

the latitude and longitude coordinates on 

their initial visit. Also, the enumerators 

were to record any problems in finding the 

previously laid out units and whether the 

GPS receiver was helpful or not. Appendix 

A provides a copy of the Enumerator 

Feedback Form. 

The GPS receiver training required 

only 15 minutes since all but two field 

enumerators had used the receivers before. 

See Appendix B for a copy of the field 

enumerator instructions on how to use the 

GPS handheld receiver for the Wheat 

Objective Yield Survey. 

5. FIELD EXPERIENCE 

 The author of this report was 

provided with an opportunity to work with 

two field enumerators on the WOY. The 

following excerpts are from notes made 

following those field trips. 

“On the first day, after reaching the 

sampled field, the weather turned for the 

worse and it started raining. The sample 

unit was easy to find by noting the red 

ribbon and poles. The previously recorded 

coordinates of the unit matched those of my 

GPS receiver. The rain made it impossible 

to record the counts onto the paper form 

since the paper was turning to mush. 

However, I also brought a Trimble Geo-XT 

GPS receiver. This particular receiver is 

designed to handle harsh environments and 

contains a built in personal digital assistant 

(mini-personal computer). Hence, I was 

able to use Microsoft Word and input the 

counts into a blank Word document using 

the stylus. A stylus is a pen-like writing 

instrument used for data entry and screen 

navigation. Once back inside the vehicle, I 

brought up the Word document and the field 

enumerator recorded the counts onto the 

paper form. This was great for the field 

enumerator, since the enumerator didn’t 

have to remember the counts which could 

lead to errors. The enumerator asked when 

we would be issuing these Trimble GPS 

receivers. However, with a list price of 

$4,500 to $5,000 per receiver, the cost is 

impractical for WOY. The unit’s high price 

is due to having a built in personal digital 

assistant, provides a level of accuracy of 

within 3 feet and is durable to withstand 

harsh weather conditions. 

 On the second day, I met a different 

field enumerator and I followed by vehicle 

to the sampled field. Upon reaching the 

supposed sampled field, we started looking 

for the red ribbon to mark the entry path to 

the unit. We couldn’t find the ribbon so we 

picked a reasonable point and walked in to 

where the enumerator thought the unit was. 

After 20 minutes or more of wandering 

around we decided to use the GPS receiver 

and realized that we were several hundred 

feet off. We got back into our vehicles and 

drove until the GPS receiver’s numbers 
5 

roughly matched the coordinates recorded 

from the initial visit. Immediately the field 

enumerator saw the red ribbon and the 

poles marking the unit. The data were then 

successfully collected.” 

 Hence, the author was provided with 

first hand experiences on how handheld GPS 

receivers can help in field data collection. 

6. RESULTS 

 Despite being a requirement, only 

107 of the 160 Enumerator Feedback Forms 

were returned. The following 

findings/numbers are based on these 107 

feedback forms. 

 On the initial visit to the field, one 

enumerator complained about the batteries 

dying on them in the field and another stated 

that it took thirty minutes to get a reading 

due to cloud cover. 

 On the follow-up visits, there were 

four times that the GPS receivers helped in 

locating a unit. The other data collection 

times, the field enumerators had no trouble 

finding their units. Although this number of 

uses is low, it was not unexpected. 

Examining the years 2000 through 2004, the 

number of times that a Washington WOY 

unit had to be laid out again averaged 8 

times. However, for 2005 there was only 

one unit that could not be located on a 

subsequent visit and had to be laid out again. 

This was due to the agricultural operator 

harvesting the field before the enumerator 

was able to take final counts. According to 

the WA FO, this mishap is highly unusual. 

Typically, the agricultural operator notifies 

the enumerator a few days before harvesting 

the field. Determining why units had to be 

laid out again in other years, was not 

possible since the questionnaires were 

shredded. Of course, there is always the 

possibility that 2005 was a fluke. Hence, a 

review of the past six years indicated that 

the year with the fewest number of times 

that a unit had to be laid out again was the 

year when GPS receivers were used. See 

Table 1. 

Table 1: Re-Laying of Wheat Objective 

 Yield Survey Units by Year 

Year Sample 

Size 

No. of Units Laid Out 

More than Once 

2005 160 1 

2004 160 6 

2003 160 4 

2002 160 10 

2001 160 8 

2000 151 12 

 Finally, field enumerators did report 

wanting to learn how to set “waypoints” 

with the GPS receiver. A waypoint is a 

stored latitude/longitude coordinate in the 

receiver. Theoretically, the enumerators 

could have recorded the sampled units’ 

coordinates in the device and then during a 

return visit the receiver would have 

displayed the direction to and the distance 

from the unit. However, to keep the level of 

instruction simple, the WA FO had decided 

to only instruct the enumerators on the 

basics and perhaps next year introduce more 

advanced features as they become more 

familiar with using the receivers. 

7. COST - BENEFIT ANALYSIS

 A cost-benefit analysis was 

conducted to determine if using GPS 
6 

receivers for the Wheat Objective Yield 

Survey is practical and cost efficient. 

 The cost breakdown is as follows. 

The Garmin GPS-72 receivers were already 

purchased for the ARMS Phase II. Hence, 

no additional costs for the receivers were 

incurred. Had this not been the case, 23 

handheld GPS receivers, at $150 a piece, 

would have cost $3,450. 

 Miscellaneous expenditures were 

estimated at $50. This includes the purchase 

of spare AA batteries (2 extra batteries per 

enumerator), paper to print the GPS 

instructions on, etc. 

 The GPS training of the twenty-three 

enumerators was expensed at $68, including 

salary and benefits. Costs of the hotel 

rooms and conference room were excluded 

since the GPS training was incorporated into 

the regularly held WOY workshop. 

 As far as WA FO staff expenses, a 

statistician spent one hour total in preparing 

training materials and in training the field 

enumerators. 

 Hence, the total expenditures for the 

research project were $118 and 1 hour of a 

WA FO statistician’s time. See Table 2. 

Table 2: Research Project Expenses 

Item Details Costs $ 

23 GPS Receivers 1/ Re-used receivers from ARMS Phase II. 0 

Miscellaneous Supplies Batteries, paper, etc. 50 

Enumerator field time (salary & 

benefits) 2/ No additional field time recorded. 0 

Enumerator Mileage Not Applicable. 0 

Enumerators Training (salary & 

benefits) 2/ 15 minutes per enumerator. 68 

WA FO Staff 1 hour (preparation and training of 

enumerators). N/A 3/

Research Project Total Costs 118 

1/ Purchasing twenty-three GPS receivers would have cost $3,450. (Priced at $150 per receiver.) 

2/ All enumerator costs were based on each enumerator’s actual time and salaries. The average salary of the 

 enumerators was $9.80 per hour. The average salary and benefits of the enumerators (using NASS’ formula 

 of (salary*1.0763)*1.11) calculates to $11.71 per hour. 

3/ Staff salaries and associated benefits expenses were absorbed by the field office. 
7 

 

On the benefits side, the GPS handheld 

receivers did help the field enumerators 

locate four units in subsequent field visits. 

Although the field enumerators may have 

found these units without the GPS receivers, 

their use did save the enumerators an 

immeasurable amount of time and ensured 

that the time series of the data was not 

compromised by having to lay out a 

replacement unit. 

 Also, the enumerators were using the 

receivers for the June Area Survey, showing 

that the receivers can be used for multiple 

surveys at the same time. 

 Finally, usage of the GPS receivers 

appeared to almost eliminate units having to 

be laid out more than once.

8. CONCLUSION 

 As field offices start acquiring GPS 

receivers for data collection activities, then 

using GPS receivers for the Wheat Objective 

Yield Survey will be practical since the 

additional cost will be minimal. Also, as the 

enumerators’ GPS skill level increases, they 

will be able to enter and locate waypoints 

which should increase the usefulness of the 

receivers. To date, NASS has successfully 

tested three ways to use GPS receivers for 

data collection: for the Agricultural 

Resources Management Survey – Phase II, 

for the June Area Survey and now for the 

Wheat Objective Yield Survey. 

9. REFERENCES

Gerling, Michael. 2005. “Using Handheld 

 Global Positioning Receivers for Phase II 

 of the Agricultural Resource 

 Management Survey.” RDD-05-04, 

 United States Department of 

 Agriculture, National Agricultural 

 Statistics Service. 

Gerling, Michael. 2006. “Using Global 

 Handheld Positioning Receivers for the 

 June Area Survey” RDD-06-02 United 

 States Department of Agriculture, 

 National Agricultural Statistics Service. 
8 

 

Appendix A 

Field Enumerator Feedback Form 
9 

Wheat Objective Yield Survey - Global Positioning System Research Project 

Enumerator - Feedback Form 

 

Enumerator ID

 

Sample Number 

Initial Visit 

1. Did you have any problems using the GPS receiver to record the location of the units? 

Yes No

If Yes, Please note the Problem(s) and the Unit ( 1 or 2 ) referred to. 

Second Visit

1. Was the GPS receiver used in locating Unit 1? 

 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

 

2. Was the GPS receiver used in locating Unit 2? 

 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

Third Visit 

1. Was the GPS receiver used in locating Unit 1? 

 

 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

 1 
10 

 

2. Was the GPS receiver used in locating Unit 2? 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

Fourth Visit 

1. Was the GPS receiver used in locating Unit 1? 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

 

2. Was the GPS receiver used in locating Unit 2? 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

 

Fifth Visit 

1. Was the GPS receiver used in locating Unit 1? 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

 

2. Was the GPS receiver used in locating Unit 2? 

 Yes Was the receiver helpful? Save any time? Please elaborate: 

No

 OVERALL COMMENTS on using the GPS Receiver

2
11 

 Appendix B 

Field Enumerator Instructions On How To Use 

The Garmin GPS-72 Receiver 
12 

Overview and Field Enumerator Instructions 

on Using Garmin Global Positioning System Receivers 

for the Wheat Objective Yield Survey

 United States Department of Agriculture 

 National Agricultural Statistics Service
13 

Table of Contents 

Introduction .......................................................................................................... 1 

The Research Project .......................................................................................... 2 

What is GPS? ....................................................................................................... 3 

Overview of the Garmin GPS (Model No. 72) ....................................................... 4 

Interface Keys .................................................................................................... 5 

GPS Receiver Instructions “Laying out the Units ................................................... 7 

GPS Receiver Instructions “Subsequent Visits ..................................................... 9 

Appendix A - Initializing the GPS Receiver .......................................................... 14 

Appendix B - Format Adjustment of the Location Box ........................................... 15 

Appendix C - Installing the Batteries........................................................................ 18 
14 

Introduction

The Research and Development Division and the Washington Field Office (WA FO) are 

conducting a research project on using handheld Global Positioning System (GPS) 

receivers for the Winter Wheat Objective Yield Survey. 

Currently, field enumerators go to specified areas of pre-determined winter wheat fields, 

lay out two objective yield units and record various crop counts. Field enumerators 

return to the same locations every month until the fields are harvested, and record 

various crop counts. Sometimes a field enumerator has difficulty finding the same 

location again and, on a few occasions, is unable to find the same location. This costs 

NASS in field enumeration time, and in those instances where the units are unable to be 

found again, the data quality suffers. 

Hence, the research project=s primary goal is to see if GPS receivers can help field 

enumerators locate those units. 

1 
15 

The Research Project

Thirty three Washington FO field enumerators have been be provided with a handheld 

GPS receiver. This should provide most enumerators working the Winter Wheat 

Objective Yield Survey with a receiver. 

For all of Washington=s 160 Winter Wheat Objective Yield sample, field enumerators will 

use their GPS receivers to record the latitude and longitude coordinates of both units 

when they are initially laid out. The latitude and longitude coordinates will be recorded in 

two places. First, on the outside of their manila kit envelopes (one envelope per sample 

is provided) and, second, on their Part B form. 

The Part B form will be returned to the office. Hence, the WA FO will have a copy of the 

coordinates, which will be beneficial if the original enumerator is unable to work and a 

different field enumerator or an office staff need to visit the field and record counts. 

Upon subsequent field visits, if the enumerators have difficulty finding the units, they may 

use the coordinates on their kit envelope and their GPS receiver to find the unit of 

interest. The GPS receivers have an accuracy level of 10 to 50 feet which is dependent 

on the number of satellites that the receiver is able to acquire. Hence, field enumerators 

may still have to look around for the unit. 

The enumerators will also be supplied with a form to record any problems in using the 

GPS receivers for determining the latitude and longitude coordinates on their initial visit. 

They will also be able to record any problems in finding a previously laid out unit and if 

the GPS receiver was helpful or not. 

2 
16 

What is GPS?

GPS stands for Global Positioning System. This system is comprised of at least 24 

satellites that orbit the earth. These satellites transmit signals to global positioning 

system equipment on the ground, like the GPS receiver that each of you have been 

provided. 

The GPS receiver acquires signals from these satellites. Thus, the receiver requires an 

unobstructed view of the sky. The GPS receiver is able to determine the location of the 

satellites since this information is included in the satellites= transmissions. Next, the 

receiver determines the distance it is from each satellite. Finally, (without getting too 

technical), the receiver is able to determine where it is actually located on the Earth 

within a certain amount of accuracy. 

The receiver will display its location in latitude and longitude coordinates. Latitude 

measures the distance North or South from the Equator while longitude measures the 

distance East and West from the Prime Meridian. 

A common use of these devices is for hiking. Hikers utilize these receivers to trace their 

trail or to mark a unique location that they would like to return to. 

Hence, a GPS receiver is not a remote control for the television but rather a 

sophisticated electronic device that can tell the user where he/she within 50 feet, speed 

of movement, which way North is, and even the distance to a particular point of interest. 

However, for this research project, we are only interested in recording the latitude and 

longitude of the units and the ability to return to the same locations at a later date. The 

next few pages will discuss the GPS receiver and what you will need to do to 

successfully use the device. Welcome to the World of Global Positioning. 

3 
17 

Overview 

of the 

Garmin GPS (Model No. 72) 

Below is a general overview of the receiver that you have been provided. 

 Internal Antenna 

4 
18 

Interface Keys

POWER Used to turn the unit on and off. To turn the unit off, press the POWER key and hold 

 it. The POWER key is also used to display the adjustment window for the back light 

 and contrast. To activate the back light/contrast adjustment window, press and 

 release the POWER key. 

PAGE Cycles through the five main display pages in sequence. 

MENU Used to display the page option menus. If pressed twice, the Main Menu will be 

 displayed. 

 

ENTER Used to confirm a selection. 

QUIT To cycle through the five main pages in reverse sequence. The QUIT key will also 

 end an operation in progress and display the previous page. 

ROCKER Located in the center of the keypad, is used to control the Up/Down and Left/Right 

 movement of the cursor on the display pages and during data entry. 

GOTO, IN, and OUT keys will not be needed for this study. If additional information is needed 

on these keys please see the provided Owner’s Manual. 

5 
19 

GPS Receiver Instructions 

ALaying out the Units@

Step 1: When you lay out the units, take out your GPS receiver. 

Step 2: Press the POWER key to turn on the GPS receiver. 

Step 3: A Warning screen will appear. Press the PAGE key and wait for the unit to 

acquire the satellites (up to five minutes). For best results, the receiver=s 

internal antenna (Page 4) should be facing up at the sky. 

Step 4: The GPS Information page showing the location coordinates should 

appear. The page should look similar to the one shown below. 

Note: The receiver=s level of accuracy is displayed in the upper right 

portion of the screen titled ACCURACY. 

6 
20 

Note: If the GPS Information page does not appear, press the PAGE key 

to cycle through the five main pages of the device. 

Step 5: Verify that the Location box is showing degrees, minutes and 

seconds. An easy way to check this is to look at the latitude coordinate 

and make sure that it has a " after the last number. 

The Location box displays the latitude (N for North) and the 

longitude (W for West) of where the receiver actually is. 

In Step 3, the GPS Information Page displayed the following

location:

 N 37E 45' 27.3" 

 W110E 41' 31.4"

N 37E 45' 27.3" is read as: 

37 degrees, 45 minutes and 27.3 seconds North. 

W 110E 41' 31.4" is read as: 

 110 degrees, 41 minutes and 31.4 seconds West. 

If the Location box does not display the coordinates in this format, 

please go to Appendix B to re-format the way your GPS receiver

displays information. 

7 
21 

Step 6: Record the latitude and longitude coordinates from the GPS receiver onto 

the labels provided on Form B and on your kit envelope. Using the 

example from Step 4, one would record the following for latitude and 

longitude. 

 Unit 1 

LATITUDE LONGITUDE 

N 37 . 45 . 27.3 W 110 . 41 . 31.4 

 dd mm ss.s ddd mm ss.s 

Step 7: Repeat the process for Unit 2. 

Step 8: Complete the AWinter Wheat Objective Yield Enumerator GPS Receiver 

Feedback@ Form. 

8 
22 

ASubsequent Visits@

Only use these instructions if you are unable to locate the unit of interest. 

Step 1: Press the POWER key to turn on the GPS receiver. 

Step 2: A Warning screen will appear. Press the PAGE key and wait for the unit

to acquire the satellites (up to five minutes). For best results, the 

receiver=s internal antennae should be facing up at the sky. 

Step 3: The GPS Information page showing the location coordinates should 

appear. The page should look similar to the one shown below. 

Note: If this page does not appear, press the PAGE key to obtain this 

screen. 

The receiver=s level of accuracy is displayed in the upper right 

portion of the screen titled ACCURACY. 

9 
23 

Step 4: In Step 3, the GPS Information Page displayed the following location: 

 N 42E 17' 26.1" 

 W 110E 39' 41.5"

 N 42E 17' 26.1" is read as: 

42 degrees, 17 minutes and 26.1 seconds North. 

W 110E 39' 41.5" is read as: 

110 degrees, 39 minutes and 41.5 seconds West. 

Step 5: Review the coordinates that you have on your kit envelope=s label for Unit 

1. 

Example is shown below: 

 Unit 1 

LATITUDE LONGITUDE 

N 42 . 17 . 25.0 W 110 . 39 . 12.3 

 dd mm ss.s ddd mm ss.s

Step 6: The goal is to have the latitude and longitude coordinates on your GPS 

receiver match those on the kit envelope=s label. Walk around with the 

GPS receiver and see how the seconds change first, next minutes, and 

finally the degrees. Walking North and South affects latitude, while 

walking West and East affects longitude. 

Compare the latitude and longitude coordinates provided on the GPS 

receiver with those on the kit envelope. 

If the coordinates are different, you will need to determine how far away 

you are by looking at degrees, minutes and then seconds. 

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The following distance conversions will help you determine how many feet or miles 

away you are from the unit. 

 Latitude 

1 degree = 69 miles 

1 minute = 1 mile = 5,280 feet 

1 second = 100 feet 

Longitude 

1 degree = 47 miles 

1 minute = 3/4 mile or 4150 feet 

1 second = 70 feet 

Hence, one degree of latitude is about 69 miles while one second is about 

100 feet away. Depending on the distance, you must determine whether 

to walk or drive in the direction that brings you closer to matching the 

coordinates on the kit envelope. An example on how to do this is 

provided on page 13. 

Note: PLEASE minimize the amount of walking through a farmer’s 

field. Sometimes, it may be best to walk back out of the field 

and walk towards the direction of interest outside of the field. 

Step 7: Locate the unit and proceed with your counts or if still unable to find the 

unit, lay out the unit again per the Interviewer’s Manual. 

Step 8: Complete the “Winter Wheat Objective Yield Enumerator - GPS Receiver 

Usage: Feedback Form”. 

Important: Please carry an extra set of AA batteries with you. When the batteries are 

 running low, a low battery warning will appear that will not disappear 

 unless new batteries are installed. See Appendix C for instructions on 

 how to install a new set of batteries. 

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Example of Using the GPS Receiver to Find a Unit

An enumerator is unable to find Unit 1 and therefore powers on his/her GPS 

receiver. The receiver displays the following coordinates: 

 GPS Receiver 

 N 42E 17' 26.1" 

 W 110E 39' 41.5"

Next, the enumerator looks at the coordinates displayed on the kit envelope=s 

label. 

 Kit Envelope=s Label for Unit 1 

LATITUDE LONGITUDE 

N 42 . 17 . 25.0 W 110 . 39 . 12.3 

dd mm ss.s ddd mm ss.s

The enumerator now focuses on latitude and notices that the first two sets of 

numbers are identical (42 and 17). However the third set, seconds, is different. 

Comparing the seconds of the GPS receiver to those on the kit envelope, the 

enumerator calculates 26.1 minus 25.0 = 1.1 seconds. Hence, the enumerator is 

about 110 feet north of Unit 1. 

Next, the enumerator looks at longitude, the first two sets of numbers are 

identical. However, the third set is different. 41.5 - 12.3 = 29.2 seconds. This 

means that the enumerator is about 2,044 feet (1/3 of a mile) west of Unit 1. 

Therefore, the enumerator should walk southeast to locate Unit 1.

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Appendix A 

Initializing the GPS Receiver

The Washington SSO should have initialized your receiver. However, if it is unable to 

locate the satellites, please do the following steps. 

Step 1: Take the unit outside where it will have an unobstructed view of the sky 

and turn it on by pressing the POWER key. 

Step 2: Press the PAGE key to bypass the Warning Screen. 

Step 3: If the receiver is unable to acquire enough satellites an options page will 

appear. 

Step 4: Using the ROCKER key, select >New location= then press then ENTER

key. 

Step 5: Next, select >Automatic= and press the ENTER key. 

This will allow the unit to continue initializing. This selection will force the

unit to search for all satellites. It may take a little longer for the unit to 

become operational using this method. 

A screen that looks similar to the one displayed below should appear. If not, please 

repeat the above process and if this does no=t work, call the office for additional 

instructions. 
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Appendix B 

Format Adjustment of the Location Box

The office should have pre-set the format of the Location box for your GPS device. 

However, if you notice that the format is no longer in degrees, minutes, seconds, then 

you will need to re-set the location field from hdddE mm.mmm= to hdddEmm=ss.s@. 

Having the device display in the latitude and longitude coordinates correctly is critical to 

having a successful research project. The following steps will guide you on how to reset the Location box=s format. 

Step 1: Press the POWER key to turn the unit on and then press the PAGE key. 

You should be at the screen shown below. 

Step 2: Press the MENU key. The following screen should appear. 

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Step 4: Using the ROCKER key, rocker down to the Setup option and press the 

ENTER key. The screen shown below should now appear. 

Step 5: Using the ROCKER key, rocker over to the right to the Location tab. 

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Step 6: Using the ROCKER key, rocker down once to the Location format and 

press the ENTER key. 

Step 7: Using the ROCKER key select hdddEmm=ss.s@ and press the ENTER key. 

Step 8: Press the MENU key three times to return you to your original screen. 

You should see your new location format. 

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Appendix C 

Installing the Batteries

Step 1: Remove the Battery Cover by turning the D-ring 1/4 turn counter clockwise 

and pulling the cover loose. 

Step 2: Check the battery polarity with the molded diagram in the battery 

compartment and install the two AA batteries inserting the end toward the 

spring first. 

Step 3: Re-install the Battery Cover by reversing Step 1. 

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