TWiST
Spatial Data
What is Geographic Spatial
Data?
What are its Properties
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Where in the World…
• On the globe the coordinate system is
Longitude (X) and Latitude (Y)
North Pole
Lat = 30º
Long = -60º
Lat = 0º
Lat = Zero Greenwich
Goes 0 to 180 west and east
Long = zero at the Equator
Goes 0 to 90 North and South
Lat = -30º 
South Pole
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-76.19 degrees west
of meridian through
Greenwich, England
43.07 degrees N of
the equator
How do we locate Syracuse on earth?
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43.07 degrees N of the equator
-76.19 degrees west of meridian through
Greenwich, England
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Can’t Xerox the Globe!
• For a paper map have to convert Long,
Lat to some other coordinate system
that will work on a flat surface.
• This conversion is called a “Projection”
• You can’t do a projection with out
distortion of the globes surface
features!
• For Example…
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The world in Geographic
Coordinates
Is
Antarctica
Really that
big?
Not!
This is a Cartesian (rectilinear) Projection
Projection
and shows a lot of distortion
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Projections
• There are many Projection in use
today (math example?)
• Some examples are…
Albers equal area
Mercator
Albers
Peters
Polyconic
Lambert equal area Azimuthal
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BUT, you don’t need to know that!
• Some of the spatial data you can get
from the web is in Long, Lat.
• Use of that data causes problems
• So most of the data you will see will
be in a Coordinate System
– State Plane – different for each state.
– UTM (Universal Transverse Mercator)
• A common map is the USGS Quad
Sheet…
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USGS 7.5 MIN QUAD MAPS
•These maps have
coordinates in their
margins of
•Long Lat
•State Plane
•UTM
•Available in:
•Paper
•Digital Image
•Digital data layers
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Google Maps
• Google maps
also have a
coordinate
system
• That’s how
your navigator
works!
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Spatial Data
• There are several types of spatial
data
– “Vector” types where all data is a point,
a line, or an area (polygon)
– “Raster” Types where earth’s surface is
represented as a grid of cells
• Elevation data
• Image data
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Areas
Lines
Points
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Raster Data
• Elevation
Raster. Each
cell has a value
that is elevation
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UTM Zones
Most of NY is in
UTM Zone 18
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UTM Coordinates
Northing
O(~4,000,000) m in NY
• The units in UTM are usually Meters
• You need to specify the zone
O(~100,000) m
in NY
Easting
• Example: Location of Syracuse is ~:
406,534 Meters E, 4,766,472 Meters N,
UTM Zone 18, N
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State Plane Zones
NY East
Zone 4801
NY Central
Zone 4826
NY West
Zone 4851
NY Long Island
Zone 4876
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Definition
Scale =
distance on map(distance unit)
distance on ground (distance unit)
A Scale of 1/24,000 means
1 inch (or foot, or furlong) on the map =
24,000 inches (or feet or furlongs) on the
ground.
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So?
• Why do you need to know this stuff?
• Because spatial data won’t overlay
neatly if data is not in same spatial
parameters
• BUT, most Geographic Information
Systems will convert data if it is not
in the same coordinate system as the
First data layer added to a project.
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You do need to know some of
this material
That is why we have provided
you with a Spatial Data
Manual
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