Apps4 finland shapefiles, wgs84 and other odd terms
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Shapefiles, WGS84 and other odd terms Workshop on Open Location Data Pekka Sarkola
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Transcript of Apps4 finland shapefiles, wgs84 and other odd terms
Shapefiles, WGS84 and other odd terms
Workshop on Open Location Data
Pekka Sarkola
2 21/09/2011
History
Finland first time on the map by Jacob Ziegler (1532)
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File formats
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Roughly 2000 – 3000 coordinate systems
Around 300 commonly used GIS file formats
Combination
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Coordinate systems
Cartesian coordinate system
Polar Coordinate system
Geographic coordinate system
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Coordinate systems – no problems...
What is origin?
What is direction?
What is unit of measurement?
You have choices:
Thousands of different coordinate systems
Good ones and bad ones
Old vs new
Local vs global
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Geographic Coordinate Systems
Latitude (leveys), longitude (pituus) and ellipsoid height
Common datums / geodetic systems
WGS 84, 72, 64, and 60
ETRS89
NAD83 / NAD27 : USA
OSGB36: GB
ED50: European Datum
Hayford International 1924: base of
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Demo
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Map projections: Basic challenge
Your paper map and your computer screen is flat
World is not!
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Map projections
Always distortion of
Area
Shape
Direction
Bearing
Distance
Scale
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Universal Transverse Mercator (UTM)
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Finnish Coordinate Systems
Kartastokoordinaattijärjestelmä (KKJ)
Old one, from 1970’s
Map projection:
Transverse mercator, 6 zones
EUREF-FIN
New, based on ETRS89
Several map projections
ETRS-TM35FIN
ETRS-TM21, 27, 33
ETRS-GK19-31
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Web mercator
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Georeferencing, geotagging,
Georeferencing
”To georeference something means to define its existence in
physical space”, Wikipedia
Especially for aerial and satellite imagery
Geotagging
Add coordinates to single item, like picture taken with mobile
phone
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Geocoding
• Transform address / place name to coordinates
D2.8.I.5 INSPIRE Data Specification on Addresses – Guidelines
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Questions?
