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

Cartesian Coordinates

Common Data Models

Vectors Define Discrete Features

Three Types of Vector Features

Vector Topology Topology – geometric properties that to not change with shape: Adjacency, connectivity, containment

Rasters – Fixed Cell Size, Grid Orientation

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