Earthsys 144: Fundamentals of GIScience
Projections and Coordinate Systems
where is your data? gis.stanford.edu
The Size & Shape
of the Earth
(Less complicated, but somehow more complicated, than you think)
Text
spherical vs ellipsoid?
surface & ellipsoid coordinates
the geoid
But, really...
- Mount Everest: About 8,848 meters
- Mariana Trench: About 11,034 meters
- Diameter of the Earth averages 12,742 km
Calculate the ratio of the Earth's variance to its diameter:
Ratio=19.882 km12,742 km≈0.00156
Apply this ratio to the diameter of a billiard ball to find the scaled variance:
Scaled Variance=57.15 mm×0.00156≈0.089 mm Scaled Variance=57.15mm×0.00156≈0.089mm
So, if the Earth were scaled down to the size of a billiard ball, the variance in its surface "smoothness" would be less than 0.089 mm.
World Pool-Billiard Association (WPA) equipment specifications, a billiard ball must be uniform with a tolerance of +/- 0.127 mm
geographic vs magnetic north
geographic coordinate systems
(Laying a "frame of reference" on the Earth)
coordinates
Geographic Coordinate Systems
longitude, con't
coordinate notation
coordinate notation, con't
How many locations can one place have?
datum (geographic) transformations
Public Land Survey System (PLSS)
Public Land Survey System (PLSS)
projected coordinate systems
(because the Earth isn't flat, but our desktops are.)
Projected Coordinate Systems
projected coordinate systems
projections & coordinate systems
projections & coordinate systems
projections & coordinate systems
projections & coordinate systems
projections & coordinate systems
Lambert conformal conic
Transverse Mercator
state plane coordinate systems
projections & coordinate systems
The "special" case of Web Mercator
(The "Map Projection" you are most familiar with!)
web map tiling schema
https://a.tile.openstreetmap.org/2/2/1.png
https://a.tiles.mapbox.com/v4/mapbox.satellite/2/2/1.jpg
Credit: @chris_whong