Title: Spatial Data Model: Basic Data Types
1Spatial Data Model Basic Data Types
- 2 basic spatial data models exist
- vector based on geometry of
- points
- lines
- Polygons
- raster based on geometry of
- grid cells (images, bitmaps, DEMs)
2Vector Data
3Vector Data Model
Points represent discrete point features
each point locationhas a record in thetable
airports are point features each point is stored
as a coordinate pair
4Vector Data Model
Lines represent linear features
each road segmenthas a record in thetable
5Vector Data Model
node
node
- Lines start and end at nodes
- line 1 goes from node 2 to node 1
- Vertices determine shape of line
- Nodes and vertices are stored as coordinate pairs
6Vector Data Model
Polygons represent bounded areas
each bounded polygonhas a record in thetable
landforms and water are polygonal features
7Vector Data Model
- Points are discreet
- Nodes
- Vertices
- Lines
- Nodes
- Vertices
- Arcs
- Closed area (Lines points ) polygons
8Vector Data Model
Vector data formats available in ArcGIS ESRI
GeoDatabases ESRI shapefiles ArcInfo coverages
and libraries CAD files (AutoCAD DWG, DXF
microstation DGN) StreetMap files Spatial
Database Engine (SDE) data ASCII point coordinate
data Linear measure (route) data
9Vector Data Model
ESRI Geodatabases Geodatabase can store many
files from many source formats 1st preferred
vector format in ArcGIS Rapid display Fully
editable (coordinate and tabular) in
ArcGIS Convenient storage format Data sets are
either point or line or polygon
10Vector Data Model
- ESRI shapefiles
- 2nd preferred vector format in ArcGIS
- Rapid display
- Fully editable (coordinate and tabular) in ArcGIS
- Simple in structure
- Do not use arc-node topology
- Connected lines do not necessarily share a
common node - Adjacent polygons do not share common bounding
arcs - Data sets are either point or line or polygon
11Vector Data Model
Shapefile polygon spatial data model
- less complex data model
- polygons do not share bounding lines
12Vector Data Model
ArcInfo coverages Commonly found format (due to
ArcInfo market dominance) Data model more
complex Display more slowly in ArcGIS Coordinate
data not editable in ArcGIS Polymorphic
(point/line/polygon/route/annotation/) Problemati
c OS file structure
13Vector Data Model
ArcInfo coverage spatial data model
- polygons share bounding lines
- same topological rules can be built into
Geodatabase
14Vector Data Model
- ASCII coordinate data
- Easy to obtain from a variety of sources
- GPS
- Traverse (survey)
- Direct reading
- OS and application independent
15Vector Data Model
Characteristics Features are positioned
accurately Shape of features can be represented
correctly Features are represented discretely
(no fuzzy boundaries) Not good for representing
spatially continuous phenomena Potentially
complex data structure (especially for polygons)
- can lead to long processing time for
analytical operations
16Raster Data
17Raster Data Model
origin is set explicitly cell size is always
known cell references (row/column
locations)are known cell values are
referencedto row/column location values
represent numerical phenomena orindex codes for
non-numerical phenomena
18Raster Data Model
A few different types of raster data
- digital elevation model (DEM)
19Raster Data Model
Characteristics Rectangular grid of square
cells Shape of discrete polygonal features
generalized by cells Continuous (surface) data
represented easily Simple data structure
20Raster Data Model
Good at representing continuous phenomena, e.g.,
Wind speed Elevation, slope, aspect Chemical
concentration Likelihood of existence of a
certain species Electromagnetic reflectance
(photographic or satellite imagery)
21Ecological Applications Vol. 17, No. 2, pp.
508526. LINKING OCCURRENCE AND FITNESS TO
PERSISTENCE HABITAT-BASED APPROACH FOR
ENDANGERED GREATER SAGE-GROUSE Cameron L.
Aldridge and Mark S. Boyce
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24Well_dst 10m cont. distance to nearest standing
energy well Rd_dst 10m cont. distance to
nearest road SB 10m cont. sagebrush cover
determined from a.p. Crop_dst 10m cont. distance
to nearest cultivated land pCrop 10m
cont. prop. of crop in a 1-km moving window
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29Homework
- Read getting data into ArcGIS Maps, displaying
layers, changing layer display properties,
project and data management, sample data,
data export - Assignment 2. Introduction to GIS
- (due January 22)