Earthsys 144: Fundamentals of GIScience

Projections and Coordinate Systems

where is your data? gis.stanford.edu

Lab Hours

• Section 1: Tuesdays, 12:00-2:50PM, Mitchell A65
• Section 2: Thursdays, 12:00-2:50PM, Mitchell A65
• Section 3: Fridays, 1:30 - 4:20PM, Mitchell A65

Office Hours

• Rebecca: Tuesdays, 10:00-11:30AM, [Old Union 1st Floor, starting Week 2]
• Mitchell: Tuesdays, 3:00 - 4:30 PM, [location TBD]
• Luke: Wednesdays, 3:00 - 4:30 PM, [Geo Corner]

The Size & Shape

of the Earth

spherical vs ellipsoid?

the ellipsoid

surface & ellipsoid coordinates

the geoid

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:
 

$\text{ Scaled Variance}=57.15\text{mm}\times 0.00156\approx 0.089\text{mm}$
 

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

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

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

web map tiling schema

https://www.maptiler.com/google-maps-coordinates-tile-bounds-projection/#3/15.00/50.00

https://docs.microsoft.com/en-us/bingmaps/articles/bing-maps-tile-system

https://a.tile.openstreetmap.org/0/0/0.png

https://a.tile.openstreetmap.org/15/5263/12704.png

https://a.tile.openstreetmap.org/2/2/1.png

https://a.tiles.mapbox.com/v4/mapbox.satellite/2/2/1.jpg

Credit: @chris_whong

common vector file formats

• shapefile
• geojson
• KML
• tabular data

common raster file formats

• GeoTiff
• COG (Cloud Optimized Geotiff)
• Esri GRID

other common file formats

• Esri file geodatabase
• SQL databases