Geography 241 – GIS I Dr. Patrick McHaffie Associate Professor Department of Geography Cook County, % population < 5.
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Geography 241 – GIS I Dr. Patrick McHaffie Associate Professor Department of Geography Cook County, % population < 5
What is a GIS? Geographic Information System - collection, organization, maintenance, analysis, and output of spatially- referenced information. Two important components - What, and Where
We usually understand GIS to be computer- facilitated system GIS is NOT only software/hardware Also includes: Trained personnel Supporting Institution Protocols for use
GIS Hardware Typical of most computer systems, with a little more storage, a few added tools for input/output. Coordinate input devices are the primary “specialized” hardware. Digitizing TabletsGPS receivers.
INPUT ANALYSIS STORAGE OUTPUT Digitizing Graphic editing, error correction: sliver removal, data sanitation, Tabular data entry and editing Data reduction Text conversion Graphic analysis capabilities - topology creation, reclassification, buffer, overlay, network, neighborhood functions, coordinate management Database manager Statistical functions Map composition Color palette generation Symbol generation, editing Graphic overlay Screen query Geographic query GIS Software
What is in it for me? Take a sheet of paper, put your name and major at the top. Then, In a five minute free write, answer the question: How can you imagine you might be using GIS and other Geotechnology in 5 years?
phenomena that exist An abstraction, relevant phenomena and properties computer representation
REPRESENTATION AND DATA STRUCTURES Coordinates and Attributes
Many objects for a theme, with properties recorded for each object
REPRESENTATION AND DATA STRUCTURES Most common data models define thematic layers Typically, layers, one layer for each distinct view of a theme
Rasters – Discrete or Continuous Features discretecontinuous
Raster – The Mixed Pixel Problem Landcover map – Two classes, land or water Cell A is straightforward What category to assign For B, C, or D?
Summary GIS are systems for the creation, maintenance, analysis, and conveyance of spatial data We represent abstractions of our world into spatial and attribute components using data models and data structures Two major data models – raster and vector