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GIS I - Group B (Data Models (Raster (Field) Data Model (Continuous Data…
GIS I - Group B
Data Models
Vector (Object/Feature) Data Model
Discrete Objects
Lines
coordinate pairs linked by arcs
Points
Coordinate pairs
Polygons
defined by
Data Structures
Coverages
Topological
geospatial and attribute (nonspatial) data in separate files
Shapefiles
Created for ease of data transmission
Geodatabases
attribute data and geometry data together in one file
Topolgical
Adjaceny
Connectivity
Containment
Raster (Field) Data Model
Continuous Data
Thematic
each cell has classified value
Image
pictures; aerial or remotely sensed
have to manually classify data into cells
File compression
quad-tree
run length
Cell Values
Discrete categorized data Represented by integers
Value Attribute Table (VAT) attached to categorize data
Sensor Data Represented by Floating Point Cell Values
used when each cell may have it's own unique value
File Types
Lossy
JPG,
Loss-less
TIFF (Tagged Image File Format), GeoTIFF
Conversions between Vector & Raster increase errors
Spatial Data Acquisition
Remote Sensing
Active Systems
Lidar
ICESAT-2
Passive Systems
Gravity detection
GRACE Satellite pair
Satellites, Aircraft, Telescopes
Electromagnetic Radiation
Field Data Collection
Coordinate Systems & Map Projections
Geographic Coordinate Systems
Datums: measurements that define shape and size of the earth
the difference between the model and the real world features need to be defined.
need a starting point (0,0)
world geodetic system(WGS); North American Datum(NAD27 or 83)
need to know model being used for the earth
Projections
georeferencing: way to measure and locate geographic features on the earth
unique
shared
persistent through time
example: place names; latitude and longitude
3 primary types
Conical
Cylindrical
map data is projected onto a cylinder wrapped around the globe, intersecting at 1 or 2 lines of secant
Planar
map data is projected onto a flat plane that intersects the globe at 1 point or 1 line of secant
distortions are unavoidable
shape
area
distance
Attribute Data
stuff?
Maps & Data Entry
Geographic Information System