Phisan Santitamnont 1

Mapping Standards

Assistant Prof. Dr. Phisan SantitamnontFaculty of Engineering,

Chulalongkorn University

Phisan Santitamnont 2

Phisan Santitamnont 3

Acquiring Spatial Data

สถาน�ฐานบนหม�ดทราบค�าพ�ก�ดและระด�บเคร��องร�บส�ญญาณจ�พ�เอสชน�ดสองความถ��

พ�#นท��บ�นถ�ายภาพ

เคร��องบ�นถ�ายภาพต�ดต�#งเคร��องร�บส�ญญาณจ�พ�เอสชน�ดสองความถ��

ดาวเท�ยมจ�พ�เอส

Phisan Santitamnont 4

EXIF GPS Photo

Google Picasa and Google Earth

Phisan Santitamnont 5

Geospatial Information System

Phisan Santitamnont 6

Type of Spatial Data

• Feature : spatial data based on mathematical vector model

• Gridded data : are sampling of spatial quantity and stored in array. It also include imagery, picture etc.

Phisan Santitamnont 7

Feature Data / Spatial Data(vector)

• จ�ด (point)

• เส�น (line)

• ร�ปป ด(polygon)

• สปาเก�ตต�� (sphagetti)

Phisan Santitamnont 8

Gridded Data and Imagery(Raster Data)

Population Density

(US Landscan 2005)

Over Bangkok and it vincinity

Orthophoto Map

From Land Development Dept.

http://www.ldd.go.th

Phisan Santitamnont 9

Map Representation

• Figure, Number, Coordinate– Digital Map, GIS

• Paper Map– Topographic Map

• Raster Map– Rasterized Topo Map, Orthophoto Map

Phisan Santitamnont 10

Topographic Map

• Base map for every countries by some national mapping agency e.g. Royal Thai Survey Department : RTSD

• Scale ranging from 1:250,000 to 1:50,000– Small-scale / medium-scale / large-scale

(1:5,000 … 1:500)• For local / regional area , scale may range

from 1:25,000 down to 1:1,000• Now-a-day likely to be compliment with

Satellite Imagery Map

Phisan Santitamnont 11

(Raster) Map Resolution

• Size of individual pixel representing map• Individual pixel represent a ground pad• Ground Sampling Distance (GSD)

Phisan Santitamnont 12

Orthophoto Map

GSD= 1. meter GSD= 15 / 30 meter

Phisan Santitamnont 13

Pictorial Map

Phisan Santitamnont 14

GSD = resolution

• Resampling (average) ground pad represents the physical (social, environment and social as well)

Phisan Santitamnont 15

GSD and Positional Accuracy

• GSD may or may not relevant to the positional accuracy

• High resolution satellite map are emerging and widely available.

• High resolution satellite map are developed with different levels of processing , accuracy ranging from <1 meter to 1 KM

Phisan Santitamnont 16

GSD and Positinal Accuracy

• Man can estimate the position on raster map upto ½ pixel

• In general maximum mapping accuracy will be not higher than ½ pixel

• E.g. IKONO Image with complex processing can give ~ 1 meter accuracy

Phisan Santitamnont 17

Satellite Image Map

• Ground Sampling Distance : 0.5 meter to 15 meter

• Price : 10 USD … 300 USD per Sq.KM.• Price : 300 Baht … 12,000 Baht per Sq.KM

• Available from Thai Geospatial Information and Space Technology Agency (Public Organization) : GISDA (http://www.gistda.or.th)

Phisan Santitamnont 18

Map Scale

Phisan Santitamnont 19

Map Scale

• Ratio of the distance measurement between two identifiable points on a map to the same physical points existing at ground scale

Phisan Santitamnont 20

Plotting Error

• In general human or plotter has plotting error ~ 0.25 mm.

• e.g. map scale 1:1,000 , plotting error on groud ~ 0.25 meter

Phisan Santitamnont 21

Allowable Error

• Since human or plotter may not locate point finer than limit plotting error.

• It is unnecessary to acquire to position more accurate than plotting error allowable error.

• Exception for digital map , one can keep all the accurate digit from surveying

Phisan Santitamnont 22

Class of Map Scale (ASPRS)

• Large Scale Map : 1:20,000 or larger

• Small Scale Map : 1:20,000 or smaller

Phisan Santitamnont 23

Large Scale Map

• Site and Corridor Construction• Urban planning and management• Flood control and emergency

Phisan Santitamnont 24

Small Scale Map

• landuse and land-cover map• Global and regional planning

Phisan Santitamnont 25

Digital Map

• Today , it trends to mix small scale digital map with large scale digital map.

• One has to understand map accuracy and resolution correctly.

Phisan Santitamnont 26

Spatial Reference System

The Earth is not flat!!!!

Phisan Santitamnont 27

Reference Coordinate System

• In general on can describe any position by specifying by using– Geographic Coordinate– Rectangle Coordinate (x,y) e.g. Universal Transverse Mercator : UTM)

Phisan Santitamnont 28

Geographic Coordinate System

• Unique to any position on the earth• Correspond to the Global Postioning

System (U.S. GPS)• Application is complicate : eg. Calculate

distance, area and azimuth

Phisan Santitamnont 29

Rectangle Coordinate System

• Projection onto a plane using mathematic relation (projection)

• Applicable on limited area on the earth• Calculation is simple : distance , area,

azimuth.

Phisan Santitamnont 30

Geographic Coordinate System

• Assumption : the figure of the Earth is Sphere.– Average radius 6,371 KM

• Assumption : the figure of the Earth is ellipsoid– Resulting from Global Geodesy and Satellite Geodesy– Current best approximation :World Geodetic Reference

System 1984 (WGS84)

Phisan Santitamnont 31

The Earth is Spheroid

ϕλ

Reference Meridian

Equator

Phisan Santitamnont 32

The Earth is an EllipsoidEllipsoidal Coordinate System ,

Geodetic Coordinate System

Nϕ

λ

Phisan Santitamnont 33

In fact , the Earth is like a potato

Phisan Santitamnont 34

Map Projection

Phisan Santitamnont 35

Map Projection

• Map is plane. The Earth is Ellipsoid.• To determine the relation between the

position on the Ellipsoid and the position on the map , we call ‘map projection’.

Phisan Santitamnont 36

Map projection

• During map projection developed , distortion will be introduced.

Phisan Santitamnont 37

Globe Project on Different GeometriesGlobe Project on Different Geometries

Phisan Santitamnont 38

Example of Map Projections

Phisan Santitamnont 39

Example of Map Projections

Phisan Santitamnont 40

More Example on Projection

Phisan Santitamnont 41

The Universal Transverse Mercator Projection (UTM)

Phisan Santitamnont 42

การฉายแผนท�� (Map Projection)

One of these types is called Mercator

Phisan Santitamnont 43

Universal Transverse Metercator (UTM)

Phisan Santitamnont 44

UTM (Universal Transverse Mercator)UTM (Universal Transverse Mercator)

• Divided into sixty longitudinal zones• Each zone is six-degrees in width extending

three degress on each side of the central meridian

• UTM is applicable between latitude 84N to 80S

Phisan Santitamnont 45

Phisan Santitamnont 46

Phisan Santitamnont 47

UTM• A conformal mapping• Origin is at the equator• Starting for Northing 0 meter

– South : 500,000 meter• Starting for Easting = 500,000 meter• Scale Factor at central meridian =0.9996• Scale factor is designed so that the error in distance

calculation will be less than 1:2,500

Phisan Santitamnont 48

scale factor = δ / ∆ UTM scale factor

= 0.9996 … 1.0004

A B

Distance on the Earth (∆)

A BDistance on UTM (δ)

A B

Phisan Santitamnont 49

Scale factor on UTM• Ranging from 0.9996 to 1.0004• Result in scale or distance discrepancy less than 1

to 2,500 • E.g. a distance of 2,500 meter obtained on UTM

map will differ from the actual distance on the Earth less than 1 meter.

• E.g. calculated distance of 1 kilometer on UTM map, it result errors on Earth 0.4 meter

• However this relation is calculable via mathematic formulae.

Phisan Santitamnont 50

Thailand is covered by UTM zone number 47 and 48

Phisan Santitamnont 51

Common Pitfalls:UTM zone 47 และ48• points at the same latitude

and are the same distance form its central meridians will have the same coordinate

• There is often noting zone number in overlapping area between zone 47-48

Overlapping Area

zone47

zone48

99° 105°

Phisan Santitamnont 52

Geog.and UTM Coordinate Conversion using FWTools / cs2cs

> cs2cs +proj=latlong +ellps=WGS84 +to +proj=utm +zone=47 -v

> 100.0000 14.0000 Enter• > cs2cs +proj=utm +zone=47 +to

+proj=latlong +ellps=WGS84 -v > 600000.0 2000000.0 Enter

Phisan Santitamnont 53

Map Datum

Phisan Santitamnont 54

Datum

• The figures of the Earth are determined with numerous technologies and evolving.

• Before GPS era, most of the nation have its own figure of the Earth, so called local datum.

• Local datum can best served local map coordinate projection and simplify calculation

Phisan Santitamnont 55

Official Thailand Datum

• Indian Datum 1975 : using Everest Spheroid 1930– Everest (1830) a=6,377,276.345

b=6,356,075.413 f=300.801697979 India• World Geodetic Coordinate System 1984

(WGS 84)– WGS-84 (1984) a=6,378,137

b=6,356,752.3142 f=298.257223563

Phisan Santitamnont 56

Local and Global Datum

Thailand

WGS-84

Indian 1975

Phisan Santitamnont 57

Datum Transformation• Once the relationships between two datum is

established. One can convert coordinate from one datum to another.

• Currently Thailand is improving mapping standards and changing parameters for datum transformation.

• Official announcement of datum parameters can be obtained from the Royal Thai Survey Department (RTSD) or the National Land Parcel Center of Department of Land (DOL) (กมร. 102-2551/2551).

Phisan Santitamnont 58

Datum Transformation

• Before 2008 the transformation parameters are:– ΔX= -206 m., ΔY=-837 m., ΔZ=-295 m.

• Starting from 2008 the transformation parameters are changed to : – ΔX = - 204.5 m ΔY = - 837.9 m ΔZ = - 294.8

m.

Phisan Santitamnont 59

ค)าพาราม+เตอร-การแปลงระหว)าง Indian Datum 1975 และ

World Geodetic System 1984 • ΔX = - 204.5 ม.• ΔY = - 837.9 ม.• ΔZ = - 294.8 ม.• ม�ค)า RMS (Root mean square) แต)ละม+ต+ = 0.09 ม.• เอกสารอ�างอ+ง

– ประกาศกรมแผนท��ทหาร เร2�องค)าต3วแปรท��เหมาะสมในการแปลงพ2�นหล3กฐาน เม2�อว3นท�� 10 มกราคม พ.ศ. 2551)

– ระเบ�ยบส7าน3กนายกร3ฐมนตร� ว)าด�วยมาตรฐานระวางแผนท��และแผนท��ร�ปแปลงท��ด+นในท��ด+นของร3ฐ พ.ศ. 2550

Phisan Santitamnont 60

EPSG code for projections and reference datum in Thailand

• WGS84 Geographic Coord.Sys. EPSG:4326• WGS84 UTM Zone 47N EPSG:32647• WGS84 UTM Zone 48N EPSG:32648• Indian Datum 1975 Geographic Coord.Sys. EPSG: 4240• Indian Datum 1975 UTM Zone 47N EPSG:24047• Indian Datum 1975 UTM Zone 48N EPSG:24048

Phisan Santitamnont 61

Datum Transfomation

>cs2cs +proj=tmerc +ellps=evrst30 +lon_0=99 +x_0=500000 +k=0.9996 +towgs84=-204.5,-837.9,-294.8 +to +proj=tmerc +datum=WGS84 +lon_0=99 +x_0=500000 +k=0.9996

> 500000.000 2000000.000 input • 500333.01 2000236.59 -1690.79 Result

Phisan Santitamnont 62

Important Figures

• 1 degree = 60 minute = 3,600 arc second• The Earth radius is 6,371 kilometer

approximately• Thus, 1 degree is 6,371*3.4142/180. = 110

kilometer at the Equator.• Likewise, 1 second is roughly 30 meter at

the Equator.

Phisan Santitamnont 63

Geographic Coordinate

• Two types for display– Hexadecimal : deg,min,sec e.g. 100° 30’ 00”– Decimal : e.g. 100.50000

• Relationships– Dec = deg + min/60. + sec./3600.

Phisan Santitamnont 64

Accuracy of GPS and Degree Notation• Handheld GPS Accuracy is about +/- 15 meter• Since 1 arc second is approximated to 30 meter on the Earth

• Recording geographic coordinate from a GPS handheld should noted upto– 1 arc second is equivalent to +/- 30 meter nearly adequate !!!– 0.1 arc second is equivalent to +/- 3 meter adequate !!!

• Recording geographic coordinate using decimal from a GPS handheld should noted upto– 1./3600 ~ 0.0003 that is the 4th decimal point is needed.– 0.1/3600 ~ 0.00003 that is the 5th decimal point is needed.

Phisan Santitamnont 65

Direction and Orientation

Phisan Santitamnont 66

North

• True North : direction of the North Pole relative to the determined position

• Grid North : Northward direction of the grid line of the map projection

True North

Grid North

λ = 99°

θ meridian convergence

Phisan Santitamnont 67

Magnetic North

• Direction to the North according to the Earth’s magnetic field

• Serveral errors may induced ‘declination’ and local attraction.

• Achieved via metal compass or electronic compass , accuracy ranging from +/- 5 degree to 0.5 degree

Phisan Santitamnont 68

Phisan Santitamnont 69

‘GPS’ North

• Picking two coordinates from GPS and calculate direction results ‘True North’ or azimuth.

• Thus GPS North == True North !• Since handheld GPS is +/- 10 meter

accuracy, the two points has to be adequate distanced.

Phisan Santitamnont 70

Mapping Accuracy and Its Quality Assesement

Phisan Santitamnont 71

ASPRS Large Scale Mapping Accuracy Standard

Phisan Santitamnont 72

Determination of Street Accuracy

Satellite Map+/- 50 meter

Street Map+/- 10 meter+/- 2 meter

Phisan Santitamnont 73

Accuracy Determination of Digital Elevation Model

#30 m / #90 m

Phisan Santitamnont 74

Comparison of SRTM-3 and L-7018 (1:50k map)

Phisan Santitamnont 75

Map Accuracy

• Comparing the mapped location of selected well-defined points to their “true” location

• “True” location may be acquired from different surveying technique or mapping technique with higher accuracy

Phisan Santitamnont 76

www.mnplan.state.mn.us/pdf/1999/lmic/nssda_o.pdf

Phisan Santitamnont 77

Determination of Test Points

• 28 well-identified points are determined on both test map and reference mapจ7านวน 8

จ�ด ต�องเป9นจ�ดท��อย�)บร+เวณขอบพ2�นท��ทดสอบระวางแผนท��• References:

– National Mapping Program USGS, Standards for Digital Elevation Models, Technical Instruction, Part 2 Specifications,

1997.– Land Management Information Center (LMIC) Minnesota

Planning, Positional Accuracy Handbook, October 1999.

Phisan Santitamnont 78

Vertical Accuracy Statistic Worksheet

RMSE ~ propability ~66%NSSDA (Accuracy) ~ 95%

NSSDA = 1.9600 x RMSE

Phisan Santitamnont 79

Vertical Accuracy Determination

• Calculation Root Mean Square Error (RMSE)

• Height from test map• Height from reference map or

measurement• Then , Quality

Phisan Santitamnont 80

Horizontal Accuracy Statistic Worksheet

NSSDA = 1.7308 x RMSE

Phisan Santitamnont 81

Accuracy Assessment• Root Mean Square Error (RMSE) is confidential

level of ~67%• National Mapping Accuracy Standard (NMAS),

US.Bureau of the Budget, 1947 uses level of confidential 90% (Circular Mapping Accuracy Standard: CMAS / Vertical Mapping Accuracy Standard: VMAS)

• FGDC: National Standard for Spatial Data Accuracy (NSSDA) , 1998 uses level of confidential 95% (Circular Error : CE95/ Linear Error: LE95)

Phisan Santitamnont 82

Confidential Level of Accuracy• For horizontal accuracy (Circular Error)

– CMAS = CE90 = 1.5175 RMSEr

– NSSDA = CE95 = 1.7308 RMSEr

• For vertical accuracy (Linear Error)– VMAS = LE90 = 1.6449 RMSEz

– NSSDA = LE95 = 1.9600 RMSEz

Phisan Santitamnont 83

Linear Error and Circular Error• Linear Error: LE

– LE=RMSE, LE90%, LE95%

• Circular Error: CE– CE=RMSE, CE90%, CE95%

• NSSDA (Accuracy) defines LE95% and CE95%

Global Free Map and Data• Global Land Survey : GLS2005 (via NASA

glovis)• Global Land Use and Land Cover :

Globcover 2005• ASTER G-DEM 2009• SRTM DEM• Sea level rise and flood!• Land and sea level : GETASSE30 DEM• Land and bathymetry : SRTM30_PlusPhisan Santitamnont 84