Lecture02

Lecture02 - Following up on the last lecture GISs Roots in...

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1 GIS GIS ’s Roots in Cartography s Roots in Cartography Getting Started With GIS Chapter 2 Following up on the last lecture… Information ordering Organizing Data and Information Information can be organized as lists, numbers, tables, text, pictures, maps, or indexes. Clusters of information called data can be stored together as a database. A database is stored in a computer as files File systems are often hierarchical
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2 The Elements of GIS Figure 2.1 The elements of a GIS. (1) The database (shoebox); (2) the records (baseball cards); (3) the attributes (the categories on the cards, such as batting average, (4) the geographic information (locations of the team’s stadium in latitude and longitude); (5) a means to use the information (the computer). The GIS Database In a database, we store attributes as column headers and records as rows. The contents of an attribute for one record is a value. A value can be numerical or text. Flat File Database Record Value Value Value Attribute Attribute Attribute Record Value Value Value Record Value Value Value Attributes have units
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3 The GIS Database (ctd) Data in a GIS must contain a geographic reference to a map, such as latitude and longitude. The GIS cross-references the attribute data with the map data, allowing searches based on either or both. The cross-reference is a link. Cartography and GIS Understanding the way maps are encoded to be used in GIS requires knowledge of cartography Cartography is the science that deals with the construction, use, and principles behind maps A map is a depiction of all or part of the earth or other geographic phenomenon as a set of symbols and at a scale whose representative fraction is less than one to one Models of the Earth The earth can be modeled as a –sphere, –oblate ellipsoid (“spheroid”) –geoid –flat The “International Flat Earth Research Society”
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4 Equal Time? (Homer, pre 900BC) http://www.ethicalatheist.com/docs/flat_earth_myth_ch8.html Disclaimer: These maps are for entertainment use only! Do not use for navigation purposes! Earth Shape: Sphere and Ellipsoid (Spheroid) Measuring the Ellipsoid Oblate ellipsoid predicted by Newton Existing triangulation in France (Cassini-Prolate spheroid) French Academy of sciences sent expeditions to Lapland and Peru (now in Ecuador) to measure the length of a degree along a meridian La Condamine sent to Mitad del Mundo, Peru (Equador) (Bouguer, 3 deg.) Moreau de Maupertuis sent to Tornio River Valley, Finland Measuring the Ellipsoid (ctd)
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This note was uploaded on 12/28/2011 for the course GEOG 176a taught by Professor Clarke during the Fall '09 term at UCSB.

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Lecture02 - Following up on the last lecture GISs Roots in...

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