Data models'ways to store and evaluate spatial data

1
Data models.ways to store and evaluate spatial
data

• Vector
• Raster
• Raster is faster but vector is corrector

2
Two ways of looking at the world...The vector
view...

• All objects are made up of points, lines and
  polygons
• All the shape files and coverages are vector files

3
(No Transcript)
4
The stained glass window, a vector representation
of the world.
5
(No Transcript)
6
(No Transcript)
7
Vector Data...

• Each feature is made up of points, lines or
  polygons (network of arcs)
• Every feature (point, line or polygon) has
  specific information concerning
  location/contiguity and coincidence.
• These location information are Topology

8
Explicit vs. Implicit topology

• Explicit topology describes for each feature
  specific relationships between features.
• A coverage or geodatabase

9
(No Transcript)
10
(No Transcript)
11
Implicit Topology

• Shape files have implicit topology
• The boundary of a polygon is defined by the XY
  coordinates of the lines that make up the
  polygon.... If two polygons share a common
  boundary, the boundary is stored twice.
• Somewhat inefficient and provides an opportunity
  for errors to occur
• Spatial analysis is possible by comparing XY
  locations

12
Potential errors... Slivers formed by two
different boundaries ... A coverage or
geodatabase can prevent these errors where
shapefiles simply ignore the error.
13
The world of RASTER data

• Modeling... Elevation....etc.

14
The tile mosaic a raster representation of the
world.
15
The raster view of the world...

• All objects are made up of small cells (often
  squares) (this is called a tessellation)
• Each grid cell can carry a only single piece of
  identifying information e.g. elevation or land
  cover or soil type or population density
• Remote sensing data is raster based (the
  individual cells are called pixels)
• Computationally simple... Most models are raster
  based

16
(No Transcript)
17
Vector is corrector, but Raster is fasterThe
use of raster data requires the activation of the
spatial analyst extension
18
Corrector? Wait just a second!
On a 124000 quad sheet, a .5mm pencil line is
12meters on the ground... A raster with a
resolution of 12 meters will show a pencil line
as a line!
19
On a 11000000 Operational Navigation Chart the
same pencil line for a flight track is 500 meters
(1500 feet) wide
20
(No Transcript)
21
Continuous Raster Data the Digital Elevation
Model (DEM)
22
The DEM can be used in Arcview/ArcGIS, a nice
trick is to create a hillshade of the data and
use it as a brightness theme
23
(No Transcript)
24
Hypsometric tinting with Shaded relief as
brightness theme