Coordinate systems Flashcards
Geographic coordinate system
defines locations of features on a globe
Where on Earth is something
- values for lat/long on a sphere
Units of GCS
Angular and degrees
Projected coordinate system
converts a GCS to a flat surface
How to draw something on a flat surface
Units of PCS
linear, meters/feet
Datum
determines which model is used to represent the Earth’s surface
(Earth is not perfectly a sphere so there are many datums to represent different parts of the world best)
Difference between projection and PCS
projection is one piece of a PCS
Projection
mathematical algorithm that defines how to present spherical Earth on a flat surface
Projection vs. coordinate system
a projection is not a coordinate system, just an algorithm used to create a PCS
WKT
- Well known text
way of identifying a coordinate system
string that defines all necessary parameters of a coordinate system
WKID
- well known ID
unique ID for each coordinate system
ESRI or EPSG
Define projection tool
- only changes coordinate system info in the metadata, does not change coordinate values
Project tool
converts all coordinate values into new projection AND changes metdata info
Projection on the fly
ESRI process that resolves coordinate system conflicts between data and the map
All projections cause
distortions
Latitude lines
horizontal parallel lines
