### Intro to GIS

```NEW TO GIS?
Not for long!
WHAT IS GIS?
•Geographic Information System (GIS)
•“used to describe and characterize the earth
and the other geographies for the purpose of
visualizing and analyzing geographically
referenced information.” (ESRI)
•In other words you can create a visual image
that will show you where something is, what it
is, and you can find out how that something
relates to everything around it.
WHO USES GIS?
• EVERYONE!!!!!!!!
• Scientists
• Police
• Military
• Most if not all Government Agencies
• Retail
• Social Scientists
• Transportation Organizations
• And the list goes on and on
TERMS TO KNOW
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RASTER
VECTOR
ATTRIBUTE TABLE
SHAPEFILE
http://www.crwr.utexas.edu/gis/gishydro05/Introduction/TermProjects/fortson.htm
http://geog214-7.wikispaces.com/Spatial+model
RASTER
• A raster is a series of discrete squares arranged in rows and
columns.
• Each square will hold a value associated with that location.
• They are often used to show imagery, land use,
temperature, and elevation.
• There are two kinds of raster datasets:
• Discrete
• Continuous
TOPO MAP RASTER
LAND USE RASTER
ELEVATION RASTER
RASTER CONTINUED
• Discrete vs Continuous
• A Discrete raster has boundaries that are known and definable.
Examples of a Discrete object would be buildings, land parcels, water
• A Continuous raster has a surface where concentration levels or
relation is measured against a fixed point in space. Confused? The
examples make it a bit easier to understand. Examples are elevation,
temperature, and imagery.
Land Use Raster
Discrete
Elevation Raster
Continuous
VECTOR
• A vector is a feature that has a spatial reference. Meaning that each
feature has one or more x-y coordinates that form a point, line or
polygon.
• The three most commonly used vectors are:
• Point
• Line
• Polygon
VECTOR CONTINUED
• Point Feature: only one x-y coordinate for each feature. Ex:
cities, buildings, sites, trees, etc.
• Line Feature: multiple x-y coordinates connected to each other.
• Polygon Feature: multiple x-y coordinates connected to each
other that form a closed shape. Ex: counties, countries, lot
boundaries, etc.
• These features are stored as shapefiles.
POINT FEATURE
LINE FEATURE
POLYGON FEATURE
ATTRIBUTE TABLES
anything.
• This information is broken up into fields.
• Ex: names, type, concentration levels
This is an example of an attribute table. It has four features (towns) each
one having 10 fields.
SHAPEFILES
• Multiple files that when used in GIS combine to create a point, line
or polygon.
• BEWARE!!! IF YOU DELETE ONE OF THE FILES IN THE WINDOWS
EXPLORER FOLDER YOU CAN CAUSE THE SHAPEFILE TO NO
LONGER WORK! MOST OF THE SEPARATE FILES ARE REQUIRED TO
CREATE THE SHAPEFILE.
This is what the same
shapefile looks like in GIS
In a windows explorer folder
a shapefile will look like this:
WHAT MAKES UP A SHAPEFILE?
• .shp file: This is the main file that stores the features geometry.
(required)
• .shx file: This is an index file and stores the index of the feature
geometry. (required)
• .dbf file: This is a dBASE table and will hold the attributes of the
feature. (required)
• .sbn or .sbx file: This is the file that stores the spatial index of the
feature. (not required)
• .prj file: This file will store the coordinate system information used
by the feature. (not required)
• .xml file: This file will store the metadata for the feature.
• These are only the common files you will see, there are more files
that can be combined into a shapefile.
will contain information such as:
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Who collected/edited the data
What coordinate system is used
What the fields in the attribute table mean
The meaning of codes
And much more
NOW YOU KNOW A LITTLE ABOUT GIS
• Later you will learn about
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