Reviewofthe Dot Sampling Method
fora Planted Area Survey
anda Yield Survey: Solutions to
Widely Misunderstood Matters19-20 June 2019
The FAO Validation Workshop of the Project“Strengthening Agricultural Statistics and Food Security Informationin CARD Countries through South-South Cooperation”
Nairobi, Kenya
KAMIKURA, Kenji
Expert, Crop Production Survey
e-mail: kkamikura@hotmail.com

Contents
Preface……………………………………………………………………1
1 Concept of the Dot Sampling Method………………….................22 Review of ways how to use “LL Sheet for the dot sampling”: Three examples
2.1 Putting sample dots on a target region on Google Earth……4
2.2 Putting one dot per hectare……………………………………….5
2.3 Putting sample dots on scattered target regions on GoogleEarth……………………………………………………….................6
3 How to solve five issues which you might encounter on aplanted area survey with the Dot Sampling Method
3.1 Can you conduct a planted area survey every month with theMethod?......………………………………………………................8
3.2 Can you apply the Method to minor crops?............................10
3.3 Can you examine attribution of a sample dot on Google Earthfor a preparatory survey?.........................................................13
3.4 Can you introduce the Method into a statistical system inyour country?...........................................................................133.5 Can you estimate planted area using the Dot Sampling
Method much better than using the hearing method tofarmers?....................................................................................14i

4 Review of production survey with the Dot Sampling Method
4.1 Estimating production……………………………………………154.2 Selecting sample spots for crop cutting with the Dot
Sampling Method……………………………………………….…16
5 Case Study
5.1 Planted Area Survey………………………………………………18
5.2 Yield Survey………………………………………………………..20
5.3 The Results…………………………………………………………21
Reference……………………………………………………………….22

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Preface
This document is compiled to share the idea of Dot Sampling Method
among the participants of the Project.
You have learned the Method during the Project and found out lots ofpossibilities the Method has. However, I am afraid some of you may havemisunderstood the Method.
In this document, you will review the true nature of the Method, which isbased on a traditional method.
In the first section of this document, you visually review the concept of theMethod.
In the second section, you brush up three different ways of usage for “LL
Sheet for the dot sampling”.
In the third section, you learn how to solve five issues which you might
encounter on a planted area survey with the Dot Sampling Method.
1) Can you conduct a planted area survey every month with the Method?
2) Can you apply the Method to minor crops?
3) Can you examine attribution of a sample dot on Google Earth for a
preparatory survey?
4) Can you introduce the Method into a statistical system in your country?
5) Can you estimate planted area using the Dot Sampling Method muchbetter than using the hearing method to farmers?
In the fourth section, you reconfirm how to select sample spots for crop
cutting with the Method with perfect PPS, probabilities proportional to size,
without preparing a list of farmers with planted area in the target region.
In the fifth section, as a case study, you can review the result of aproduction survey using the Dot Sampling Method in Tsukuba Hamlet at the timeof a study course “JICA Knowledge Co-Creation Program on Agricultural
Statistics Planning and Designing.”

1

1 Concept of the Dot Sampling Method
The figure below shows a target region of 100 ha (W).
You are going to estimate the total area of red fields using the Dot Sampling
Method.

Let’s estimate the area of red fields above.
1) you put 100 sample dots (n) in a target region;2) you count the number of sample dots which fall on red fields=> the number of sample dots(n1) is 18;3) you estimate the red field area（𝑇̂）by multiplying the area of the target region(W) by the ratio（𝑝̂ ＝𝑛𝑛1）.
=> 𝑇̂ = 𝑝̂ × 𝑊 =18
100× 100ha = 18ha

(Precision= 21.3%, See page 12)(The precision is 6.7%, when you put 1,000 sample dots in a target region.)
2

The total area of red fields in below picture is as same as that in the picture
above. You could divide the picture below to make the picture above.
The area of red fields is 18ha (= 4ha + 8ha + 3ha + 1ha + 2ha).

32 Review of ways how to use “LL Sheet for the dot sampling”: Three examples
2.1 Putting sample dots on a target region on Google Earth
Suppose you want to put 100 dots in Lao PDR (238,000 km2), you fill in T1 Table as below.

T-1 Basic data to generate sample dots (Sampling Design)
Target area

Size of theTarget area km2

Sample size

(1)

(2)

(3)

Laos100

Note:

238000Starting point Starting point(latitude)(longitude)
(4)

100

(5)

22.52

100

Finishingpoint(latitude)

Finishingpoint(longitude)

(6)

(7)

13.88

107.72

In some cases, you have to draw a boundary line of the target
region on a map.
Fortunately, on Google Earth, international boundary lines andlarge administrative dividing lines are available. In other cases, youneed to download shapefiles of the administrative boundaries such as
GADM, the Database of Global Administrative Areas, a highresolution database of country administrative areas.
You could even create polygon of your own on Google Earth sothat you can set any shape of a target region.
42.2 Putting one dot per hectareSuppose you want to put 1 dot per 1 ha (=0.01km2) in a target region, you
fill in T-1 Table as below.
T-1 Basic data to generate sample dots (Sampling Design)
Target area

Size of theTarget area km2

Sample size

(1)

(2)

(3)

Tsukuba1dot=1ha

0.01

Starting point Starting point(latitude)(longitude)(4)

1

36.032451

Note 1:(5)140.1226

Finishingpoint(latitude)

Finishingpoint(longitude)

(6)

(7)

36.026140.1329

This method is a modern version of a Point Grid Plate Method
which may be familiar to you as it is a traditional method formeasuring area.
Note 2:
You could use this method as a two-dimensional ruler or ruler
for measuring area.

5

2.3 Putting sample dots on scattered target regions on GoogleEarth(Case1)
Suppose you want to put totally 20 dots in Central African Republic(623,000km2) and Uganda (241,000km2), you fill in T-1 Table as below.

T-1 Basic data to generate sample dots (Sampling Design)
Target area

Size of theTarget area km2

Sample size

(1)

(2)

(3)

CAfUgan20864000

Starting point Starting point(latitude)(longitude)
(4)

20

(5)

11.05

6

14.36

Finishingpoint(latitude)

Finishingpoint(longitude)

(6)

(7)

-1.56

35.07

(Case2)
Suppose you want to put 6 dots on rice fields in Tsukuba Hamlet, you fill in
T-1 Table as below, when the total area of rice fields in Tsukuba Hamlet is0.1225km2.
T-1 Basic data to generate sample dots (Sampling Design)
Target area

Size of theTarget area km2

Sample size

(1)

(2)

(3)

JICA 6 (0.1225)

0.1225

Starting point Starting point(latitude)(longitude)(4)

636.032451

7(5)140.1226

Finishingpoint(latitude)(6)

36.026

Finishingpoint(longitude)(7)

140.1329

3 How to solve five issues which you might encounter on aplanted area survey with the Dot Sampling Method
3.1 Can you conduct a planted area survey every month with theMethod?
(Solution)
The Method is the only one solution for conducting planted area survey everymonth with less monetary and human resources. Once you put sample dots on
the target region, you can use the same sample dots for years afterwards.
(Explanation)
The following is an example of a project to conduct a planted area survey
every month, so that you can get planted area of each crop every month inthe target district.
1) First step (In the first year of the project)
You put 1,000 sample dots in the target district. And you decide sample
dots to visit which have possibility to fall on cultivated land.
(Suppose the share of cultivated land is 40% of the target district, thenumber of sample dots to visit is 400 in a district.)82) Second step (From the second year of the project)
An extension worker in a village visits same sample dots every month to
examine which crops are planted at the sample dots.
(Suppose there are 80 villages in a district and 400 sample dots to visit
in a district, the average number of sample dots to visit in a village is 5.)3) Third step
You estimate planted area of each crop every month.
(Suppose 80 sample dots fall on rice, you can estimate the planted areaof rice with the precision of 10.7%.) (See page 12)93.2 Can you apply the Method to minor crops?
(Solution)
The method can apply to minor crops. You can estimate planted area of minorcrops in a target region with the Dot Sampling Method.

(Explanation)
With the Method, sample dots are selected in proportional to planted area.
Every dot has same probability, so the appearance ratio of each crop is to be
proportional to the planted area of the crop.
You only need to put the number of dots required for the survey.
Two tables on following 2 pages show the number of sample dots required
for a survey.
1) The first table shows the number of sample dots required by aimed
precision for a preparatory survey.
2) The second one shows precision by the number of sample dots for apreparatory survey.
Note: Two tables on following two pages are for a preparatory survey.
In case of a field survey, you visit only sample dots which havepossibilities to fall on the target crop planted spots, so the number ofsample dots you visit at the time of a field survey is less than thenumber shown in two tables for a preparatory survey.

10

The Number of Sample Dots Required by Aimed Precision
for a Preparatory Survey

11Precision by the Number of Sample Dots for a Preparatory Survey

123.3 Can you examine attribution of a sample dot on Google Earthfor a preparatory survey?
(Solution)
The Method works well, even if you cannot examine attribution of dots on GoogleEarth.
(Explanation)
Please don’t worry. The role of a preparatory survey is not to examine
attribution of sample dots but divide sample dots into two categories.
First category is sample dots which you need to conduct a field survey andanother category is sample dots which you don’t need to conduct a field survey.
If you cannot examine attribution of a dot, you categorize the dot into asample dot which you conduct a field survey.

3.4 Can you introduce the Method into a statistical system inyour country?
(Solution)
At a first step, you could use the method for evaluation of the appropriateness ofthe official data of a pilot village, instead of introducing the Method into a statisticalsystem in your country.

(Explanation)
You could make a plan of a project titled “Evaluation of the appropriatenessof the official data on rice planted area of a pilot village.”In the project you validate the official data on rice planted area of a pilot
village through conducting a rice planted area survey using the Dot Sampling
Method in a pilot village. You may conduct a workshop and compare the official
data with the result of the project and study the better methodology of a rice
planted area survey.

13

3.5 Can you estimate planted area using the Dot Sampling
Method much better than using the hearing method to farmers?
(Solution)
The hearing method has not solved lots of problems yet such as; farmers don’tknow the true value with evidence; you cannot choose sample farmers properly
because of lack of population. But the Dot Sampling Method has solved theseproblems already.

(Explanation)
You might think that it is common to ask farmers to get data throughinterpersonal hearing method.
This hearing method is popular in some cases, but it has a weak point thatyou cannot evaluate a validity of the data, as it is often happened that farmers
don’t know the true value.
There are many advantages in using the Dot Sampling Method as follows.
1) You can get figures without bias, as survey object is not a person but aland.
2) You don’t have to develop a statistical population for a survey, as theMethod doesn’t require a population.
3) You conduct a planted area survey any time you like with less monetaryand human resources, as you can use same sample dots for years.
4) You can calculate precision of the results, and it is empirically more precise
than theoretical precision.

14

4 Review of production survey with the Dot Sampling Method
4.1 Estimating production
A production survey consists of two surveys: a yield survey and an areasurvey.

Production survey = Yield survey + Area survey
Note: “Yield” is used as “production per unit area”
In order to estimate the amount of production in a region, you multiply
average yield in the region and total planted area in the region together.

Total production in the target region=Average yield in the target region
×
Total planted area in the target region(Point to notice)
Please exclude a dyke area from a total planted area in order to avoid
overestimating production, when an average yield is calculated without dyke.
(See the table on page 19)
On the contrary, please include a dyke area into a total planted area, when an average
yield is calculated with dyke.

154.2 Selecting sample spots for crop cutting with the Dot
Sampling Method
One of most important activities of a yield survey is to select sample spots
for crop cutting.
In order to get an average yield of the target region, you need to selectsample spots for crop cutting with PPS, probabilities proportional to size.
With the Dot Sampling Method, you can select sample spots with perfect
PPS without preparing a list of farmers with planted area in the target region. Youcan dramatically streamline the process of selecting samples as well as
estimating the average yield by simple average.
Suppose you are going to select 6 sample spots for crop cutting using theDot Sampling Method. You have two ways of option as follows.
(First option)
Suppose you know the results of a planted area survey and 49 dots (CodeNo12 in the figure below) out of 80 dots fall on rice planted spots, you extract six
sample dots for crop cutting out of 49 dots using systematic sampling method.

16

(Second option)
If you haven’t conducted a planted area survey with the Dot Sampling
Method, you can use an alternative way.
Suppose you know that area of rice field in the target area is 0.1225 km2,
you fill in necessary data in “LL Sheet for the dot sampling”.
Then you visit every dot in the target area and check the attribution of each
dot at the field, and you find six dots on rice fields.
T-1 Basic data to generate sample dots (Sampling Design)
Target area

Size of theTarget area km2

Sample size

(1)

(2)

(3)

JICA 6 (0.1225)

0.1225

Starting point Starting point(latitude)(longitude)(4)636.032451

17

(5)

140.1226

Finishingpoint(latitude)(6)

36.026

Finishingpoint(longitude)(7)

140.1329

5 Case Study
The followings are the result of a production survey using the Dot Sampling
Method in Tsukuba Hamlet at the time of a study course “JICA Knowledge CoCreation Program on Agricultural Statistics Planning and Designing.”

5.1 Planted Area Survey
You conduct planted area survey by putting 80 sample dots in Tsukuba
Hamlet.

18

19

5.2 Yield Survey
You conduct a yield survey by selecting 6 sample spots for crop cutting.
(See page 16)20

5.3 The Results
You estimate production of rice in Tsukuba Hamlet.

21

Reference
KAMIKURA, Kenji: Planning and Designing of Crop Production Survey:“Let’s estimate the total rice production in Tsukuba Hamlet”, JICA
Knowledge Co-Creation Program on Agricultural Statistics Planning andDesigning, JICA Tsukuba International Center, 22 - 29 August 2018
JINGUJI, Issei: Comparison of FAOSTAT statistics and Dot Sampling survey
Estimates of the harvested area of oil palm in Indonesia, Malaysia andThailand, Kyoto University Academic Center for Computing and MediaStudies, July 2018(https://repository.kulib.kyotou.ac.jp/dspace/bitstream/2433/233867/1/wps_8.pdf)
Team Dot Sampling, MAFF Japan: The Dot Sampling Method, 29 March 2016
KAMIKURA, Kenji: What you can do with the Dot Sampling Method using
Google Earth, Fifth meeting of the Regional Steering Committee for Asiaand the Pacific for the Global Strategy to Improve Agricultural and Rural
Statistics Bangkok, Thailand, 9 December 2015
JINGUJI, Issei: Dot Sampling Method for area estimation, CROPMONITORING FOR IMPROVED FOOD SECURITY, FAO & ADB, 2014(http://www.fao.org/fileadmin/templates/rap/files/Project/Expert_Meeting__17F
eb2014_/P11_Dot_sampling_method_for_planted_area_estimation_using_Goo
gle_earth_ __land_use_survey__FAO_RAP_17_Feb_2014.pdf)
KAMIKURA, Kenji: Package of Agricultural Production Survey, AfricaRice,Cotonue, Benin, March 2013(https://wpqr4.adb.org/LotusQuickr/agstatap/Main.nsf/0/6716E47F1793360B48
257B5D002EC9F4/$file/Package%20of %20Agricultural%20Production%20Sur
vey.pdf)
JINGUJI, Issei: How to Develop Master Sampling Frames using Dot
Sampling Method and Google earth, December 2012(http://www.fao.org/fileadmin/templates/ess/global_strategy/PPTs/MSF_PPTs/
5.MSF_Dot_sampling_method_on_Google_Earth_Jinguji.pdf)
KAMIKURA, Kenji: Estimation of Planted Area using the Dot Sampling
Method, FAO APCAS 24, October 2012(http://www.fao.org/fileadmin/templates/ess/ess_test_folder/Workshops_Events/APCAS_24/Paper_after/APCAS-1221_Planted_Area_using_Dot_Sampling.pdf)
YATES, Frank: Sampling Methods for Censuses and Surveys, Charles
Griffin & Co. Ltd., 1949
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