Rebecca Boger Earth and Environmental Sciences Brooklyn
College
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What is GIS? Functions Features Attributes Data models and
databases Vector Raster Geodatabases How do we know where are we on
the Earths surface? Datum Projection Coordinates ArcGIS
overview
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Computer system hardware Geographically referenced digital data
Computer software that carries out various management and analysis
tasks People
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1. Much information has a spatial and / or temporal component
Location Pattern Trend 2. Quick and easy access to large and varied
amounts of data Search and update data Model Analysis 3. Output
capabilities maps, graphs, statistics tailored to desired
needs
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Visualization Looking at data on a map to get information see
relationships Geodata management Updating and organizing data to be
useful Analysis Applying tools to answer questions and support
decisions
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Uses of GIS are almost limitless and apply to most every field
Source:
http://www.colorado.edu/geography/gcraft/notes/intro/intro_f.html
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Location: Where is it? Condition: What is it? Trend: What has
changed? Routing: Which is the best way? Pattern: What is the
pattern? Modeling: What if?
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Analysis : applying tools to geographic data to answer
questions Example: Suppose you own a several coffee shops and want
to expand in the same city Question: What are the potential areas
for a new shop?
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Shape Location Symbol Attributes
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What is GIS? Functions Features Attributes Data models and
databases Vector Raster Geodatabases How do we know where are we on
the Earths surface? Datum Projection Coordinates ArcGIS
overview
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Raster: continuous data, imagine a grid placed over the Earths
surface Vector: discrete objects lines, points and polygons
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Each cell (pixel) has one value distributed over the entire
area Reality there may be variance within the area E.g., mapping
elevation data with a cell size of 30mx30m Apply a mean, median or
modal value, or other type of representation Can also be coded for
categorical data (non numeric), such as land cover type Can convert
between raster and vector
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Spatial data Data with some form of spatial or geographical
reference Can be located in 2- or 3-dimensional space Attribute
Data Describes the characteristics of spatial features Examples: Is
it green or blue? How much is it worth? When was it built? Usually
stored in a relational database that is linked to spatial data
files
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Information stored in tables Each row called a record Each
spatial feature is linked to a record Columns or fields recording
attributes Source:
http://www.colorado.edu/geography/gcraft/notes/datacon/datacon_f.html
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Source: ArcGIS desktop help tool
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Geographic data are organized into feature classes Feature
class is a digital dataset with the same shape and attributes Layer
is a visual representation of a feature class in a map Feature
class table as one record and one column for each attribute
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What is GIS? Functions Features Attributes Data models and
databases Vector Raster Geodatabases How do we know where are we on
the Earths surface? Datum Projection Coordinates ArcGIS
overview
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How to place a 3D Earth on a flat 2D paper map Something gives
Shape Area Distance Angles A spherical globe of Earth can preserve
all
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Geodesy: science of measuring the shape of the Earth Create a
set of known locations datum Map projections transform the datum to
a flat surface
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Depiction of spherical Earth on 2D surface Many different types
Designed for different uses Extent of area covered (small or large
scale) Where on Earth Shape of area depicted (e.g., long
north/south orientation of California versus east/west orientation
of Kansas)
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Reference systems: Where are you relative to something else?
E.g., city grid and addresses Latitude and longitude Universal
Transverse Mercator (UTM)
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What is GIS? Functions Features Attributes Data models and
databases Vector Raster Geodatabases How do we know where are we on
the Earths surface? Datum Projection Coordinates ArcGIS
overview
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GIS tasks can be categorized into two main functionalities:
ArcMap: Mapmaking, editing, and spatial analysis ArcCatalog:
database design and data management; search for spatial data,
preview it, create and manage metadata Similar to working with
Windows Explorer ArcToolbox: window containing set of tools, merged
in ArcMap and ArcCatalog Overlapping functionalities
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Viewing spatial data by creating and querying a map Main
document has *.mxd extension Map document stores the layers,
symbology, and layout, but does NOT store the actual geographic
data (can be large files) Directs to where the geographic files are
located Geodatabases help with keeping track of datasets for map
project
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Manage your data: find datasets on your hard drive, copy and
move datasets around your system, document datasets with metadata
Particularly useful because a single geographic dataset is often
composed of multiple files or folders. Copying and deleting
sometimes cannot be done with using Microsoft Windows
Explorer.
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Geoprocessing Processing geographic information through
operations called commands or tools ArcToolbox important way to
conduct geoprocessing Basic analysis tools, conversion tools
(import and export), data management tools, geocoding tools, linear
referencing tools, and spatial statistic tools Extensions: provide
other tools for geoprocessing
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ESRI data structure homogeneous collection of features that can
have either point, line, or polygon shapes. package of separate
files (at least 3) with different extensions.shp: shape file,
stores feature geometry.shx: shape index, stores an index to the
feature geometry.dbf: dBase file of attribute information can be
other files