The Size & Shape

of the Earth

(Less complicated, but somehow more complicated, than you think)

spherical vs ellipsoid?

the geoid

But, really...

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 coordinate systems

(Laying a "frame of reference" on the Earth)

Geographic Coordinate Systems

longitude, con't

coordinate notation

Degrees Minutes Seconds (DMS)

📍 Latitude: 40° 42′ 51″ N
📍 Longitude: 74° 00′ 21″ W

Decimal Degrees (DD)

📍 Latitude: 40.714
📍 Longitude: -74.006

   decimal
   places   degrees     distance
   -------  -------     --------  
   0        1           111   km
   1        0.1         11.1  km
   2        0.01        1.11  km
   3        0.001       111   m
   4        0.0001      11.1  m
   5        0.00001     1.11  m
   6        0.000001    0.111 m
   7        0.0000001   1.11  cm
   8        0.00000001  1.11  mm

How many locations can one place have?

datums & (geographic) transformations

projected coordinate systems

(because the Earth isn't flat, but our desktops are.)

Projected Coordinate Systems

projections & coordinate systems

Lambert conformal conic

Transverse Mercator

projections & coordinate systems

projections & coordinate systems

projections & coordinate systems

projections & coordinate systems

state plane coordinate systems

The "special" case of Web Mercator

(The "Map Projection" you are most familiar with!)

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

Odds & Ends

Public Land Survey System (PLSS)

Public Land Survey System (PLSS)

geographic vs magnetic north

All Lab Sections will meet in the Mitchell A65 Computer Lab, located in the basement.

Facilitator                          Day & Time                   Location

Labs!

This week:

https://canvas.stanford.edu/courses/208610/assignments/691872