Mapping Standards - RIDkmcenter.rid.go.th/.../uploads/...MappingStandard.pdf · Topographic Map...
Transcript of Mapping Standards - RIDkmcenter.rid.go.th/.../uploads/...MappingStandard.pdf · Topographic Map...
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Mapping Standards
Assistant Prof. Dr. Phisan SantitamnontFaculty of Engineering,
Chulalongkorn University
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Acquiring Spatial Data
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EXIF GPS Photo
Google Picasa and Google Earth
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Geospatial Information System
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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.
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Feature Data / Spatial Data(vector)
• จ�ด (point)
• เส�น (line)
• ร�ปป ด(polygon)
• สปาเก�ตต�� (sphagetti)
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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
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Map Representation
• Figure, Number, Coordinate– Digital Map, GIS
• Paper Map– Topographic Map
• Raster Map– Rasterized Topo Map, Orthophoto Map
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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
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(Raster) Map Resolution
• Size of individual pixel representing map• Individual pixel represent a ground pad• Ground Sampling Distance (GSD)
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Orthophoto Map
GSD= 1. meter GSD= 15 / 30 meter
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Pictorial Map
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GSD = resolution
• Resampling (average) ground pad represents the physical (social, environment and social as well)
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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
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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
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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)
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Map Scale
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Map Scale
• Ratio of the distance measurement between two identifiable points on a map to the same physical points existing at ground scale
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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
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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
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Class of Map Scale (ASPRS)
• Large Scale Map : 1:20,000 or larger
• Small Scale Map : 1:20,000 or smaller
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Large Scale Map
• Site and Corridor Construction• Urban planning and management• Flood control and emergency
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Small Scale Map
• landuse and land-cover map• Global and regional planning
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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.
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Spatial Reference System
The Earth is not flat!!!!
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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)
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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
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Rectangle Coordinate System
• Projection onto a plane using mathematic relation (projection)
• Applicable on limited area on the earth• Calculation is simple : distance , area,
azimuth.
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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)
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The Earth is Spheroid
ϕλ
Reference Meridian
Equator
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The Earth is an EllipsoidEllipsoidal Coordinate System ,
Geodetic Coordinate System
Nϕ
λ
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In fact , the Earth is like a potato
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Map Projection
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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’.
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Map projection
• During map projection developed , distortion will be introduced.
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Globe Project on Different GeometriesGlobe Project on Different Geometries
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Example of Map Projections
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Example of Map Projections
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More Example on Projection
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The Universal Transverse Mercator Projection (UTM)
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การฉายแผนท�� (Map Projection)
One of these types is called Mercator
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Universal Transverse Metercator (UTM)
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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
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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
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scale factor = δ / ∆ UTM scale factor
= 0.9996 … 1.0004
A B
Distance on the Earth (∆)
A BDistance on UTM (δ)
A B
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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.
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Thailand is covered by UTM zone number 47 and 48
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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°
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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
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Map Datum
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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
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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
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Local and Global Datum
Thailand
WGS-84
Indian 1975
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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).
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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.
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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
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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
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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
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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.
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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.
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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.
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Direction and Orientation
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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
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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
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‘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.
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Mapping Accuracy and Its Quality Assesement
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ASPRS Large Scale Mapping Accuracy Standard
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Determination of Street Accuracy
Satellite Map+/- 50 meter
Street Map+/- 10 meter+/- 2 meter
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Accuracy Determination of Digital Elevation Model
#30 m / #90 m
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Comparison of SRTM-3 and L-7018 (1:50k map)
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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
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www.mnplan.state.mn.us/pdf/1999/lmic/nssda_o.pdf
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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.
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Vertical Accuracy Statistic Worksheet
RMSE ~ propability ~66%NSSDA (Accuracy) ~ 95%
NSSDA = 1.9600 x RMSE
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Vertical Accuracy Determination
• Calculation Root Mean Square Error (RMSE)
• Height from test map• Height from reference map or
measurement• Then , Quality
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Horizontal Accuracy Statistic Worksheet
NSSDA = 1.7308 x RMSE
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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)
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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
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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