Spatial Data J M Piwowar Geog 805 GIS

Spatial Data © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 1

Why is Geographical Information Special? § Integration of spatial data from various sources can be time-consuming and tedious § Updating geographic data is complex and expensive § Cartographic displays of geographic data require the retrieval of large amounts of data © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 2

Why is Geographical Information Special? § Representations of the real-world § Imprecise § Multidimensional § Voluminous § Often requires projection onto a flat surface § Requires specialized analysis methods © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 3

Why is Geographical Information Special? © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 4

How do we Represent Geography? § Space, Time, Attribute © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 5

What is a Map? § a representation, normally to scale and on a flat medium, of a selection of material or abstract features on, or in relation to, the surface of the earth § a model of spatial phenomena; an abstraction; not a miniature version of reality § a map is a cartographic abstraction © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 6

Types of Maps § topographic © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 7

Types of Maps § thematic © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 8

Important Properties of Maps § Scale § Coordinate System § Projection © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 9

Scale § The ratio between distances on the map and corresponding distances in the real world § Representations: v. Statement: 1 cm = 100 km v. Representative Fraction (RF): 1: 50, 000 v. Graphic: © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 10

Coordinate Systems § Where is the University of Regina? • City of Regina • 3737 Wascana Pkwy • S 4 S 0 A 2 • Map grid: K-11 • 50° 15’ 05” N 104° 21’ 09” W • 528904 E 5585457 N NAD 83 © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 11

Latitude & Longitude Latitude and longitude: the framework of the international reference system that pinpoints a place's absolute location. § Latitude: describes how far north or south of the equator a place is, measured in degrees. v each degree (written: 58°) is divided into 60 minutes (written: 42') and each minute into 60 seconds (written: 26"). v e. g. 58° 42' 26" N © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 12

Latitude & Longitude: position east or west of a half circle drawn from the North to the South Pole and passing through the former Royal Observatory at Greenwich, London, England. v Such lines joining places of the same longitude are called meridians of longitude. v e. g. 105° 02' 56" W © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 13

§ Polar coordinates are useful for describing locations on the globe. § But! The Earth is not a sphere. © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 14 Clarke, K. C. , 2003. Getting Started with Geographic Information Systems. . Prentice-Hall Ellipsoids

What about Elevations? § How high is something? § Sea level § Gravity models © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 15

§ Geoid models attempt to represent the surface of the entire earth over both land ocean as though the surface resulted from gravity alone. © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 16 Peter H. Dana, The Geographer's Craft Project, Department of Geography, The University of Colorado at Boulder Geoid Models

Datums § A mathematical formula that combines an ellipsoid and its geoid fit to surveyed control points. § NAD 27 § NAD 83 § WGS 84 © J. M. Piwowar Geog 805: GIS and Spatial Analysis Spatial Data 17