KAMIKURA, Kenji
Senior Statistician
Statistics Department
Ministry of Agriculture, Forestry and Fisheries
e-mail: kenji_kamikura450@maff.go.jp
e-mail: kkamikura@hotmail.com

What you can do with the Dot Sampling Method
using Google Earth
No1 Area Survey
No2 PPS Sample Selection
No3 Two-dimensional Scale

This paper has been written to describe the practical aspect of the Dot Sampling
Method. We would be glad if this document could arouse your interest in the Dot
Sampling Method. The Method enables you to conduct the theory which was discovered
long time ago but had not been practiced until Google Earth emerged. We believe theMethod has a power to reform the traditional way of Planted Area Survey or othersurveys. We hope you will challenge the Method to improve agricultural statistics.

1. What the Dot Sampling Method is in brief

1.1 You put a certain number of dots on a map.
With the Dot Sampling Method, you put any number of dots on Google Earth toconduct survey on an attribute of each dot or use dots as sample spots.
For instance, in case of a rice planted area survey in a village, with the Dot SamplingMethod, you put a certain number of dots randomly on a village and count the number ofdots which falls on planted rice and estimate the total area of rice planted field in thevillage.
Note: In order to put a certain number of dots on a region, Excel Macros have beendeveloped to put dots on Google Earth which the Method uses as a map.

1.2 The Dot Sampling Method has settled long-standing issues of agriculturalstatistics.
There have been long-standing issues on agricultural statistics. The followings aresuch issues and what the Method has resolved:
The number of human resources is limited.
→ The Method requires fewer human resources.
Staff members don’t have enough knowledge of statistics.
→ What you do is only to count the number of dots. Even the unskilled can follow
the Method.
It is almost impossible to measure the planted area even once a year.
→ The Method doesn’t require you to measure the area but count the number ofdots, so you can conduct survey any time you would like to do.
You need tremendous effort to maintain a population.
→ The Method doesn’t require a population to extract samples.
It is not easy to estimate the real value and calculate the precision.
→ The Method uses Yes/No questions to estimate the proportion of units thatpossess some characteristics or attribute or fall into some defined class, whose
theory is simple, so you can estimate the real value and calculate the precision
easily.
Non-sampling errors happen extensively.
→ With the Method, non-sampling errors hardly happen, as what you do is tocheck at a sample dot if it falls on, for instance, rice or not.
It is time-consuming to select samples for crop cutting in order to estimate
average yield in the target region.
→ The Method could be applied to not only area survey but also selectingsamples for crop cutting with Probability Proportional to Size as mentioned
later in 3.2, so you can select samples easily through the Method.
The results are not reliable.
→ With the Method, the results are reliable because of the characteristics of theMethod mentioned above.

2 Let’s use Excel Macros for Dot Sampling.
You need three files: 1) LL Table Maker
2) Save Range As KML File
3) LL Sheet for the dot sampling22.1 First Step: Put six necessary data, from (2) to (7) below, in the T-1 table of LL
sheet for the Dot Sampling.

Note for filling in: (1) Any name(2) & (3) density of dots (number of dots per area)(4) any latitude on the north of the northernmost of a target region(5) any longitude on the west of the westernmost of a target region(6) any latitude on the south of the southernmost of a target region(7) any longitude on the east of the easternmost of a target region

2.2 Second Step: Automatically sample dots are put on Google Earth.

33. With the Excel Macro, you can conduct three different activities:
With the Excel Macro, you can conduct three activities as follows:
No1: You can put any number of dots on a target region.
No2: You can put any number of dots on rice fields or any attribute in a target region.
No3: You can put a sample dot every 10a, every 1ha or any size.

3.1Activitiy No.1: You can put any number of dots on a target region.
You can put any number of dots on a target region to estimate the proportion of rice
planted area or any other attribute in a target region.
Note1: The way of estimation of area:
In case that you put 100 dots in a target region of 6,561,000ha, and thenumber of dots that falls on rice planted fields is 10,10

estimation of rice planted area is 6,561,000ha × 100 ＝ 656,100ha
Note2: The procedure of area survey:
1st: You put dots in a target region on Google Earth.
2nd: You conduct preparatory survey.
3rd: You conduct field survey.
4th: You estimate rice planted area.
Note3: The number of necessary sample dots by aimed precision:
Please see Annex.
The followings are examples of area survey.

43.1.1 Result of Preparatory Survey before conducting field survey, Sri Lanka

Source: Mr.Issei Jinguji, Dot Sampling Method for Area Estimation, February 20145

3.1.2 Result of Preparatory Survey before conducting field survey, Thai

Source: Mr. Issei Jinguji, Dot Sampling Method for Area Estimation, February 2014

3.1.3 Result of Preparatory Survey before conducting field survey, Lao PDR

Source: Mr. Sengphachanh Khounthikoummane, Lao PDR, 17 August 201463.1.4 Result of Preparatory Survey before conducting field survey, Timor-Leste

District

Sample dot

Share ofDistrict

Estimated Area
Area by(A)Wikipedia (B)
％
㎢
㎢
12.3
1,830
1,813
10.0
1,492
1,506
12.5
1,870
1,877
12.1
1,810
1,782
2.6
388
367
4.9
726
737
8.5
1,273
1,323
4.0
597
549
5.0
746
768
5.5
826
804
9.3
1,392
1,376
7.8
1,164
1,203
5.4
806
814
100
14,919Difference(A-B)

number㎢
Lautem184
17Baucau150-14
Viqueque188-7Manatuto
182
28
Dili39
21
Ailiu
73-11
Manufahi
128-50Liquiçá
60
48
Ermera75-22
Ainaro83
22
Bobnaro140
16
Cova Lima
117-39
Oecusse
81
-8
Total
1,500
0
Note１： Target region is the whole country
Note２： Total area of the target region is a total of each destrict area from Wikipedia: 14,919㎢.

3.2 Activity No.2: You can put any number of dots on rice fields or any attribute ina target region.
In case that total area of rice fields in the target region is 370km2 and you want toselect 100 samples from rice fields for crop cutting, you just put 370 and 100 in the T-1
table of LL sheet for the Dot Sampling.

You can put any number of dots in the rice fields that are selected by Probability
Proportional to Size.
So you can get not only theoretically proper spots for sampling, but also you canreduce an effort to select samples for crop cutting as well as estimate average yield in
the target region in a simple way.
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3.3 Activity No.3: You can put a sample dot every 10a, every 1ha or any size.
If you want to put a dot every 10a, for example, you just put 1km2 and 1000 dots in
the T-1 table of LL sheet for the Dot Sampling or other combinations such as 0.001km2
and 1dot.

You count the number of dots. When the number of dots is ten, the area of that
region is 0.1 ha/dot ×10 dots = 1 ha.
You can use this method as if each dot is a division of scale. This is so called a
two-dimensional ruler. In the case above, the ruler is graduated in 10a.

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4. Reference
JINGUJI, Issei: Dot Sampling Method for area estimation, CROP MONITORING FOR
IMPROVED FOOD SECURITY, FAO & ADB, 2015(http://www.fao.org/fileadmin/templates/rap/files/Project/Expert_Meeting__17Feb2014_/
P1-1_Dot_sampling_method_for_planted_area_estimation_using_Google_earth___land_use_survey__FAO_RAP_17_Feb_2014.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_D
ot_sampling_method_on_Google_Earth_Jinguji.pdf)
KAMIKURA, Kenji: Package of Agricultural Production Survey, AfricaRice, Cotonue,Benin, March 2013(https://wpqr4.adb.org/LotusQuickr/agstat-ap/Main.nsf/0/6716E47F1793360B48257B5
D002EC9F4/$file/Package%20of%20Agricultural%20Production%20Survey.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-12-21-_Planted_Area_using_Dot_Sampling.pdf)

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(Annex)
Number of Necessary Sample Dots by Aimed Precisionin case of Preparatory Survey and Field Survey

Shareofrice plantedarea
in a target
regionAimed Precision
CV = 3%

Preparatory
surveyAimed Precision
CV = 5%Preparatory
surveyField
surveyAimed Precision
CV = 10%Preparatory
surveyField
surveyField
surveyp%
1

110,000

1,100

39,600

396

9,900

99

2

54,444

1,089

19,600

392

4,900

98

3

35,926

1,078

12,933

388

3,233

97

4

26,667

1,067

9,600

384

2,400

96

5

21,111

1,056

7,600

380

1,900

95

6

17,407

1,044

6,267

376

1,567

94

7

14,762

1,033

5,314

372

1,329

938

12,778

1,022

4,600

368

1,150

92

9

11,235

1,011

4,044

364

1,011

91

10

10,000

1,000

3,600

360

900

90

20

4,444

889

1,600

320

400

80

30

2,593

778

933

280

233

70

40

1,667

667

600

240

150

60

50

1,111

556

400

200

100

50

60

741

444

267

160

67

40

70

476

333

171

120

43

30

80

278

222

100

80

25

20

90

123

111

4440

1110

Note: Calculation fomulas are as follows:
Sample size for Preparatory Survey ===Number of dots for Field Survey = Sample size for Preparatory Survey

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