Transcript No Slide Title

GIS Modeling
Week 2 — Maps as Data
GEOG 3110 –University of Denver
Presented by
Joseph K. Berry
W. M. Keck Scholar, Department of Geography, University of Denver
Points , lines, polygons and surfaces; Discrete vs.
Continuous data; Map data types and their implications;
Displaying grid data; Contouring implications; Grid map
structure and storage
Who We Are (Class Photo)
Annotated Class Roster posted at…
http://www.innovativegis.com/basis/Courses/GMcourse10/Syllabus/GM2010_roster.pdf
<as of Thursday morning>
Now, Where Were We?
What GIS Is (and isn’t)
Computer Mapping (70’s) - Spatial dB Management (80’s) - GIS Modeling (90’s)
GIS Modeling
 Spatial Analysis —
“contextual” relationships
within and among mapped
data (Reclassify, Overlay,
Distance, Neighbors)
 Spatial Statistics — “numerical” relationships within
and among mapped data (Surface Modeling and Spatial Data Mining)
From mapping to
Spatial Reasoning…
…that radically changes our Map Paradigm
…keeping in mind that the frontier is currently focused on Multimedia Mapping (00’s)
(Berry)
Campground Suitability Model Review (Logic)
Prefer Gentle Slopes, Near Roads, Near Water, View of Water and Westerly Oriented
…but can’t be too close to water or too steep
1
2
3
4
1) Base
maps
2) Derived
maps
6
3) Interpreted
maps
4) Combined /
Modeled maps
5) Constraint
maps
5
6) Final map
(Berry)
Campground Suitability Model Review (Solution)
A sequencing of map analysis commands are applied to implement model logic—
using a command script (Tutor25_Campground.scr)
Solution set
of maps are
created by
evaluating
the model
logic for the
unique
pattern of
conditions
at each
geographic
location
…grid cell
(Berry)
Hands-on
Review
Basic Map Features
Manual cartography utilizes points, lines and areas as the basic
building blocks for characterizing geographic space
Based on spatial objects (discrete)
New map feature
type based on
grid cells
(continuous)
…traditionally all maps are composed of three fundamental map features—Points, Lines
and Areas. The digital map provides additional dimensions of depth and time to
extend the features to Surfaces, Volumes, hyper-Volumes and fuzzy-Features
(Berry)
Storing Points, Lines and Areas
…how do you think Vector and Raster data structures store
Surfaces, Volumes, hyper-Volumes and fuzzy-Features?
(Berry)
Spatial Resolution
The concept of Scale (S= MD/GD) does not exist in a GIS
…heresy!!!
…replaced by the concept of Resolution (Spatial, Mapping, Thematic and Temporal)
(Berry)
Minimum Mapping Resolution
…replaced by the concept of Resolution (Spatial, Mapping, Thematic and Temporal)
(Berry)
Thematic and Temporal Resolutions
…replaced by the concept of Resolution (Spatial, Mapping, Thematic and Temporal)
…so what is the difference between the concepts of PRECISION and ACCURACY
…and how do these concepts relate to the concept of RESOLUTION?
(Berry)
Accuracy versus Precision
The Wikipedia defines Accuracy as “the degree of veracity” (exactness) while Precision as “the degree of
reproducibility” (repeatable)
Accuracy describes the closeness of arrows to the bull’s-eye at the target center (actual/correct)
High Accuracy
but Low Precision
Handheld GPS unit
Accuracy vs.
Precision
…the “target analogy”
compares measurements
to the pattern of arrows
shot at a target
High Precision
but Low Accuracy
Precision GPS unit
Precision relates to the size of the cluster of arrows— grouped tightly together is considered precise
(Berry)
Classification versus Delineation (spatial perspective)
Interpreter A
Interpreter B
Interpreter C
Vegetation
Parcel
Mapping
Accuracy = classification (What)
Photo Interpreter A
Cottonwood
Superimposed
interpretation
boundaries
Precision = delineation (Where)
Photo Interpreter B
Ponderosa Pine
Photo Interpreter C
Cottonwood
Classification Accuracy (What)  Delineation Precision (Where)
(Berry)
Model Accuracy/Precision (spatial modeling perspective)
Routing Criteria
Most
Preferred
1
2
Calibrate
Expert
Opinion
Least
Preferred
3
4
5
6
7
8
HD & VE times 10
Homeowners
9
Housing Density
Road Proximity
RP & SA times 10
Sensitive Areas
Visual Exposure
HD & RP times 10
Environmentalists
…cognitive
mapping has
no definitive
right/wrong
solution—
Engineers
Weight
Stakeholder
Values
Most
Preferred
Start
Start
Optimal Path
Optimal
Corridor
Engineers
Environmentalists
Average of
the three
cost surfaces
Homeowners
Individual
Solutions
End
Combined
Solution
End
(Berry)
Raster Data Types
It is important to note that the map features in a vector-based mapping system
identify discrete, irregular spatial objects with sharp abrupt boundaries. Other
data types — grid surfaces, raster images and pseudo grids — treat
space in entirely different manner to portray spatially continuous data
…in a raster image the values stored at each
map location identify its color (hue, saturation
and brightness)– constrained integer value
…mapped
data ready
for map
analysis and
modeling
GIS Maps contain—
• Points, lines, polygons
• Grid surfaces
• Raster images
• Pseudo grids
…in a pseudo grid each grid element
is treated as a separate polygon (square)
with spatial and attribute tables defining
the set of little polygons
(Berry)
Basic Grid Data Structure
A Grid Map consists of a matrix of numbers with a value
indicating the characteristic /condition at each grid cell
location forming a geo-registered set of Map Layers
or “Map Stack”
Lines
Layer Mesh
Map Stack
Grid Map
Fill
Analysis Frame
The Analysis Frame
provides consistent
“parceling” needed
for map analysis
and extends discrete
point, line and areal
features to continuous
Map Surfaces
Col 3, Row 22
Layer Mesh
Data listing for a
Map Stack
Drill-down
Basic Grid Display Types
Display Types…
Lattice display forms a
smooth wireframe
Grid display forms
chunky extruded grids
…so how is a Contour Map generated?
Contour line
1900
(See Example Applications, “Display Types” for more information)
(Berry)
Thematic Display (Shading Manager)
MapCalc Shading Manager…
# Ranges sets the number of intervals
Equal Ranges has the same range for each interval
Equal Count has the same number of cells for each interval
(See Example Applications, “Display Types” for more information)
(Berry)
Contouring Mapped Data (Continuous to Discrete)
Display the elevation surface
as wireframe (Lattice) with filled
floor contours
 Set #Ranges to 7 and assign
yellow as the inflection color
 Redisplay the surface as
Equal Count, Equal Ranges,
StDev and User Defined
…note the dramatic differences in the
shape and position of the boundary
lines of the discrete contour intervals
+/- 1Stdev
Equal Count
Equal Ranges
So which discrete map of elevation surface is CORRECT?
User Defined (300 Step)
(Berry)
Matching Data Types & Display Types/Forms
Data Type…
Data Type toggles
between Discrete and
Continuous data types
Display Type…
Use Cells toggles
between Lattice and
Grid display types
Display Form…
3D Toggle changes
2D and 3D display
forms
(See Example Applications, “Data Types”, “Color Interval/Pallet”, “3D Display Options” and “Data Inspection and Charting” for related information)
(Berry)
Numeric and Geographic Data Types
…all digital maps are composed of organized sets of numbers—
the Data Type determines what “map-ematical” processing can be done
with the numbers on a map, or stack of map layers
(Berry)
Homework Exercise #2
Part 1 –
Understanding Basic Concepts and Terms
• Scale and Resolution. 1) Map Scale, 2) Spatial Resolution, 3) Thematic
Resolution, 4) Minimum Mapping Resolution and 5) Temporal Resolution.
• Data Types. 1) Nominal, 2) Ordinal, 3) Interval, 4) Ratio, 5) Binary, 6) Choropleth,
7) Isopleth data types (be sure to distinguish which data types are Numeric and which are
Geographic)
• Display Considerations. You will generate different map displays of the Slope
and Districts map layers, then identify/comment on the Data Type, Display Type and Display
Form used and discuss the effects/appearance of the different displays
Part 2 –
Characterizing Geographic Space
…Discrete versus Continuous
Thematic Mapping
•
. You will use the Shading Manager to create different map displays
while investigating the effects of Calculation Mode (Equal Ranges, Equal Count,+/- 1 Standard Deviation
and User Defined), Number of Ranges and Color Ramp assignments.
(Berry)
Simple Erosion Model
(Exercise #2, Part 3)
Create a slope map
Reclassify
that map for
slope classes
Create
a flow map
Reclassify
that map for
flow classes
Combine
the maps of
slope classes and flow
classes
…result
is a map with a
2-digit code
1St digit = flow class
2nd digit = slope class
(Berry)
So Where Are You in GIS?
General and
Innovative Users– uses
…changing our Map
understanding of basic
concepts, capabilities and
considerations in developing
new applications within
their discipline
Paradigm
The “bookends” of this continuum are
the current drivers of Geotechnology
“…of the Discipline”
“…of the Computer”
“…of the Application”
Computer
Programmer–
Solutions
Developer–
Systems
Manager–
Data
Provider–
GIS
Specialist–
develops GIS
tools; mostly
computer science
with some
courses in GIS
develops GIS
applications that
link GIS to realworld problems;
mostly GIS/CS
with some
disciplinary
expertise
develops and
maintains spatial
databases and
connections
within (LAN)
and outside
(Internet) the
organization; CS
and GIS balance
develops GIS
data layers; good
skills in GPS and
remote sensing
with strong skills
in GIS data
formats and
geodetic
referencing
uses discipline
expertise and
GIS knowledge
for basic GIS
applications and
interacts with
solution
developers to
address complex
spatial problems
(See Beyond Mapping III, Topic 4, “Where Is GIS Education”)
(Berry)
Vector to/from Raster (direct calculation)
V to R– burning the points, lines and areas into the grid (fat, thin and split)
R to V– connecting grid centroids, sides and edges (line smoothing)
(Berry)
Vector to Raster (centroid implied)
V to R– uses a point file of cell centroids and converts polygon features that intersect
Implied Grid with Centroids
Centroid Point File
Vector Map (polygons)
…as the
points fall
Note: this technique
is very sensitive to
cell size (features
smaller than cells)
and complexity of
boundary shape
The corresponding
grid cell is assigned
the value of the
“point in polygon
intersection”
…but it is really fast
Raster Map
Polygons with Overlaid Points
(Berry)
Exporting MapCalc Data Layers
ESRI GridASCII Format
just for fun (you are
having fun, right?)—
Export the MapCalc Tutor25.rgs
Elevation map layer in both
…browse to an
appropriate folder and
Save exported file
ESRI GridASCII format and
Surfer ASCII format
Surfer ASCII Format
(Berry)
Grid-based Data Structures/Formats (Esri .asc)
…open the ELEV.asc file in Notepad to see the data structure (stored as
an Individual File) <export Elevation as ESRI_elevation.asc and open in NotePad>
Map Data (Bottom portion)
Origin is upperleft corner
…values along
the row, left to
right in a block
(25)
General Information (“header” first 6 records)
#Row
#Col
Longitude of LL corner
Latitude of LL corner
Cell size (in decimal degrees)
No Data value (null)
Each block
contains all of
the map values
for a row
…next row up
…repeat for all
rows (625 total)
(Berry)
Grid-based Data Structures/Formats (Surfer .grd)
…open the ELEV.grd file in Notepad to see the data structure
(stored as an Individual File) <export Elevation as Surfer_elevation.grd and open in NotePad>
Map Data (Bottom portion)
Origin is lowerleft corner
…values along
the row, left to
right in a block
(25)
General Information (“header” first 5 records)
File Type
#Row #Col
Each block
contains all of
the map values
for a row
Lon/Lat LL and UR
Min and Max Value
…next row up
…repeat for all
rows (625 total)
(Berry)
Grid-based Data Structures/Formats (MapCalc .rgs)
…open the Tutor25.rgs in Notepad to see the data structure
(stored as a Data Table)
…open Tutor25.rgs in Notepad
Map Data (Bottom portion)
Origin is lowerleft corner
…values for all
columns along
the row, left to
right (25)
General and Map Legend Information (top portion)
Each column
contains all of
the map values
for a layer
…next row up
…repeat for all
rows (625 total)
(Berry)