Post on 25-Jun-2015
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)
3 21/09/2011
File formats
4 21/09/2011
Roughly 2000 – 3000 coordinate systems
Around 300 commonly used GIS file formats
Combination
5 21/09/2011
Coordinate systems
Cartesian coordinate system
Polar Coordinate system
Geographic coordinate system
6 21/09/2011
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
7 21/09/2011
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
8 21/09/2011
Demo
9 21/09/2011
Map projections: Basic challenge
Your paper map and your computer screen is flat
World is not!
10 21/09/2011
Map projections
Always distortion of
Area
Shape
Direction
Bearing
Distance
Scale
11 21/09/2011
Universal Transverse Mercator (UTM)
12 21/09/2011
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
13 21/09/2011
Web mercator
14 21/09/2011
15 21/09/2011
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
16 21/09/2011
Geocoding
• Transform address / place name to coordinates
D2.8.I.5 INSPIRE Data Specification on Addresses – Guidelines
17 21/09/2011
Questions?