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)

spherical vs ellipsoid?

surface & ellipsoid coordinates

the geoid

But, really...

If Earth were scaled down to a standard billiard ball of 57.15 mm diameter, the difference between Mount Everest and the Mariana Trench would scale to about 0.09 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)

coordinates

Geographic Coordinate Systems

https://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~357742~90124676:No--14--Napoli,-Ischia,-Procida,-Ca?amp$3B$qvq=q:prime%20meridian$3B$sort:Pub_List_No_InitialSort,Pub_Date,Pub_List_No,Series_No$3B$lc:RUMSEY~8~1&$3B$mi=46&$3B$trs=9785&embedded=true&sort=Pub_List_No_InitialSort%2CPub_Date%2CPub_List_No%2CSeries_No&cic=RUMSEY~8~1#

https://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~352872~90120098:-2--Europe-?sort=pub_list_no_initialsort%2Cpub_date%2Cpub_date%2Cpub_list_no&qvq=q:prime%20meridian%20paris;sort:pub_list_no_initialsort%2Cpub_date%2Cpub_date%2Cpub_list_no;lc:RUMSEY~8~1&mi=2&trs=2086#

https://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~323532~90092731:Carte-de-la-Basse-%25C3%2589gypte-et-de-la-p?sort=pub_list_no_initialsort%2Cpub_date%2Cpub_date%2Cpub_list_no&qvq=q:prime%20meridian%20pyramid;sort:pub_list_no_initialsort%2Cpub_date%2Cpub_date%2Cpub_list_no;lc:RUMSEY~8~1&mi=0&trs=2#

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

Precision

   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