The Earth is Round: Mapping GPS Data with a GIS Carla McAuliffe, Ph. D. DataTools 2008 Program

Earth is Round

Consider this inflatable globe… Imagine peeling off the surface of the Earth to make a map…. What happens?

The flattened surface has gaps.

Map projections fill in the gaps.

Map projections may preserve distance, area, and/or shape, but not all three.

Three common projections

Latitude and Longitude

Alternate Origin Point (0, 0) -71.5° 41.0°

(0, 0) -71.5° 41.0° State Plane is one such alternate coordinate system. “Easting” and “Northing” values indicate the number of meters east and north of the origin. The advantage is that all coordinate values are positive. Alternate Origin Point

Everything happens somewhere: connecting data to geography Map by latitude and longitude (Add Event Theme) Register it (tie an image to a location; world files and geotiffs) Link an image to a point (hot link) Draw it on the map (digitize it) Link it to existing geography (join tables) Geocode it (map by address)

MassGIS -

MassGIS - Uses Massachusetts State Plane Mainland Zone projection, NAD83 datum

Build a base map Set up a spreadsheet Collect & convert geographic data Map, visualize, & analyze the data