INTERMEDIATE MODELING for GIS: AT echnical Primer for Advanced by lL5dDRTg

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```									                                Section II: Data Models and Data

2.1.      GIS data models
2.2.      Spatial analysis
2.3.      Surface analysis
2.4.      USGS digital data

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.1. GIS Data Models
    GIS provides a stable modeling environment
because of its Cartesian grid
    GIS employs both raster and vector
methodologies
    Topology facilitates the spatial intersect, a
function SQL is incapable
    GIS data representations may be either discrete
or continuous
    Reference frames may be 1, 2, 2½, 3 or 4
dimensional
    General GIS models may be classified as either
field, object, or network

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
    What are Geographic Information Systems?
– Automated means of compiling, storing,
displaying, and analyzing spatial data
    Three General Capabilities:
– Computer map—ties map locations to a
Cartesian grid and thus facilitates the
construction of mathematical models
– Bring life to tabular data by consolidating
information in one place using location as the
organizational key
– Facilitates the creation of new information

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
    Mechanics of Building Computer Maps:
–   Computers do nothing but add and remember
–   Easily map pictures with x-y coordinates
–   Building x-y coordinates into a “picture” requires a
stated data relationship between coordinates
–   Data may be stored like a photograph or TV picture -
RASTER where x-y coordinates hold attributes
–   Data may be stored like a stick drawing of directed
line segments - VECTOR where lines are assumed to
connect x-y locations

……………..
……………..
……………..
……………..

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
By using the mathematically relationships
between x-y coordinate in terms of
connectivity and proximity, GIS provides
the structure necessary to perform a
“Spatial Intersect”

SQL

    What is contained within a boundary area?
    What is within a distance of a boundary?
    Delete those objects contained within.

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Three Methods of Spatial
Intersect:

Graph Paper

    Connectivity: arc-node topology:
    Area Definition: poly-arc topology:                                             Tabular
    Contiguity: left-right topology:                                            Relationships of
Connectivity
Asphalt                Concrete           Asphalt         Concrete

Stacked

Coordinates
48 54                   39      49         66
25   TLMS 100001         65   0               TLMS 100002                   100

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques             Terra Genesis, Inc.
Paper
UPDATE: Merge new features

+           =

+       =

+          =

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
BUFFER:

UNION:

IDENTITY: Add common                              INTERSECT: Delete areas not
features from two maps                                common to primary

+            =                                     +        =

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Topological Relationships

   Connectivity: arc-node topology:
Spatial primitives
– Arcs must connect to other arcs at                             (line work)
nodes
– Distinguishes nodes from vertices
   Area Definition: poly-arc topology:
– Arcs that connect to surround an                                   Topological
area define a polygon                                                 rules
– First and last node are always the
same
   Contiguity: left-right topology:
Spatial
– Arcs have direction
Intersect
– Allows networks to be built
– Creates left and right polygons

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques     Terra Genesis, Inc.
Problems with Topology

    GIS is set apart from RDBMS only by its ability to facilitate
spatial intersect through topology
    Topology isolates GIS from mainstream IT
    Long proven RDBMS tools for version control and rollback
cannot be applied to GIS venues
    Breach between IT and GIS management and operation

   Topology complicates data storage through complex tabular
relationships
   The ratio of information to data is so low, it precludes large-scale
enterprise implementation without additional fixes that further
separate GIS from mainstream IT
   Low information ratios hinder Internet-enablement and client-
server optimization

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
In Large Implementations,
Data must be Tiled:

Data Lock-down a Pressing Problem

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Stacked Coordinates (Dynamic
Location):
PolyLine Event DLO
Step 1: Bring shapes together                              (no measures necessary)
Attribute A
Attribute B

0    10   20    30 40 50 60 70 80 90 100 110 120
PolyLineM Route DLO {x,y,z,m} required

Step 2: Drop Event DLO end points to Route DLO
Attribute A
Attribute B

0    10   20      30   40    50   60   70       80   90 100 110 120

Step 3: Read polyLineM as a number line to build intersect
table            ID#    From     To        Attribute
100001          4        37          A
100001         37        44         A&B
100001         44        70          B

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques    Terra Genesis, Inc.
Continuous Data Models that
do not Store Topology
    Leaner data that need not be tiled, creating a
continuous data set
    No topology implies attributes maintained with the
spatial data within an RDBMS and not a dedicated
GIS
    Spatial data within RDBMS offers temporal version
control and traditional RDBMS rollback capabilities
    Relegates GIS to RDBMS support duties
    But . . . some mechanism must be devised to
accomplish spatial intersect and connectivity

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
The Raster Data Model:

    Pixel size - picture element or tessellation:
– Larger, less resolution
– Smaller, more memory & computation intensity
    Pixel shape:
– Divisible into similar shaped units
– Distance between centers should be equidistant
    Pixel Representation:
– Cell value represents the value at the cell’s center
only
– Cell value represents the value of the entire cell face

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
(1) Selecting Pixel Shape:

Squares are divisible, but distances are
not the same in every direction

Circles are equidistant, but
cannot be divided

Triangles, Hexagons, Bucky Balls
You name it! The two design objectives
are mutually exclusive

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
(2) Selecting Pixel Size:

Cell = 1000 m                     Cell = 100 m                        Cell = 10 m

oooooooo                         oooooooo                           oooooooo
oooooooo                         oooooooo                           oooooooo
oooooooo                         oooooooo                           oooooooo
oooooooo                         oooooooo                           oooooooo

Area = 120 ha                   Area = 120 ha                     Area = 120 ha
Array = 30 x 40                 Array = 300 x 400                  Array = 3000 x 4000
Count = 1200                    Count = 120 000                    Count = 12 000 000
Memory = 4.8 kb                 Memory = 480 kb                   Memory = 48 Mb

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
(3) Cell Value Representation:

Case I-Value                                     Case II-Value
cell center only                                  entire cell face

Continuous Field                                       Discrete Entities
Floating Point Raster                                   Categorical Raster
Interpolation between values                              Interpolation not valid
No attributes assigned                                  Can attach attributes

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
    Three Classes of Data Models (ways of interpreting
data values):
–   FIELD MODEL: a continuous variation of one variable across
space
–   OBJECT MODEL: Space is subdivided into functional,
unique, and discrete units
–   NETWORK MODEL: Two dimensional representation of one
dimensional space—up a street, down a street, no node-no
turn
    How Spatial Data are Classified:
–   1-D (linear)
–   2-D (flat map - x,y)
–   2 ½-D (surface x,y,only one z per x, y pair)
–   3-D (solid - x,y,z-multiple z per x,y pair)
–   4-D (temporal - x,y,z,t)

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Field Model                       Object Model                         Network
Model
002222333322210                     111111111111111                  111100000000000
002233777775210                     999111199111111                  000110000000000
023445578887521                     991111199991111                  000011111111111
134555789876531                     999911199999111                  000010000010000
111455788875211                     999999999111111                  000010000010000
012455788775522                     444444411111111                  000010000010000
012345777774210                     444444411111111                  000010000011111

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.1. GIS Data Models
Why is topology required within vector data models?
What are the constraints associated with topology?

Describe two ways to increase query speeds when vector
topology is required.

What two rules are used to select pixel shape?

Describe interpolation in terms of continuous and
discrete data models.

What is the difference between a solid and a surface
model?

Describe a field model.

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.2. Spatial Analysis:

   The systematic and logical reduction (sifting
through) of ALL data to find the NEEDED
information
   Needle in the haystack we deal with daily
   Connect stacked maps with logical operators to
reduce the available information, or, create new
information more suited to the task
   LOCATION is used as the disparate integrator
   ASSUMES: correlations and consistencies are
easier to visualize when data are stored and
queried spatially

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
4-classes of Spatial Analysis:

Spatial Overlay &
Contiguity Analysis

Raster Analysis                                        Surface Analysis

Network
Analysis

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Spatial Overlay & Contiguity
Analysis:

   New maps created from the combination of others
   Light-table gymnastics
   McHarg 101

A firm seeks land to build a new factory:
• On a rail line
• Non-sandy soil
• Parcel > 2 hectares
• Parcel price < \$12 000 per hectare
• Population < 2000, > 750/ hectare

For a liquor license requested at 5th and Elm:
• List home owners within 500 meters
• List schools within 2 km
• List/plot liquor license count within 10 km

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Raster Analysis via Map
Algebra

•                               =

New raster = in-raster 1 • in-raster 2
Where, •, is a mathematical operator

Arithmetic, (+) (-) (x) (÷)                      Boolean, (TRUE or FALSE)
Relational, (<) (>) () ()                      Logical, if, then, else

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Local Raster Functions:
Local raster functions have a
1:1, cell to cell, correspondence
between input and output

Example per cell operators
are sine, cosine, multiply,
and divide
Input Raster
Several rasters may be
simultaneously examined on a
per cell basis to return
statistics for all corresponding
stacked cell values

Output Raster

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Focal Raster
Functions:
Target cell

Cell
neighborhood

Focal functions
cells to the target cell
to determine the
output cell value.

These types of functions
help smooth data.
Output Raster

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques    Terra Genesis, Inc.
Zonal Raster Functions

Target cell
Input
Raster             Comparison
zone

Zonal functions require two
Zone            rasters. Values from the
Raster
secondary zonal raster are
referenced during processing
of each input cell.

Output
Raster

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Global Raster Functions
Global functions generally produce a new raster that is the
solution to a problem or spatial equation:
• Path finding
• Path finding through a weighted field
• Darcy flow and dispersion
• Multivariate analysis

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.2. Spatial Analysis

What are the four types of spatial analysis?

What analysis type relies on spatial intersect
capabilities?

What is the difference between a raster and a raster
surface?

What is the primary purpose of a global raster?

How can time be viewed in a raster? How about
randomness? How about either in vector form?

Describe some raster analysis applications.

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.3. Surface Analysis

    Surface analysis looks at the slope of the line
between adjacent points of a field model
    Color models and value stretching may be used to
visualize the shape of a surface
    A zero slope is a horizontal line, and thus a contour
    A negative second derivative is concave down and
models a water shed divide
    A positive second derivative is concave up and
bounds a stream bed

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Surface Analysis:

    Finding isolines (contours), constant slope between points
    Finding slopes (1st derivatives) between points
    Finding inflexion points (2nd derivatives) between points
    Applying color models and value stretching for display

Assumes a field model, and                         •   General surface shape
so interpolation is a valid                       •   Cut and fill
mathematical operation                           •   Fluid flows
•   Visibility and view shed

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Raw Surface Data:

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
RGB Color Model

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Stretching Data Increases
Contrast

0             64            128               192             255 value

0             64            128               192             255 value

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques    Terra Genesis, Inc.
Color Model Application:

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
The Shape of a Mountain:

z
3000 m

2000 m

1000 m

Sea Level                                                                            x
1km            2 km            3 km

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Concave Down Inflection:

d2z/dx2 < 0
Local maximum
water shed boundary

Concave Up Inflection:
d2z/dx2 > 0

Local minimum
stream bed

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Concave Up:

dz/dx < 0
d2z/dx2 > 0
energy losing
depositing

Concave Down:

dz/dx < 0
d2z/dx2 < 0
energy gaining
eroding

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Raw Surface Values:

5       5       5       1       7       7       7       7         7      7

1      1       1       1       5       5      5       5          5      7

5       5       5       1       5      7       7       7          5      7

5      9       5       7       5       7      9       7          5      7

5      5       5       1       5       7      7       7          5      7

1      1       1       1       5       5       5      5          5      7

5       5       5       1       1      1       1       1          1      1

7      7       7       1       5       5      5       5          5      5

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques       Terra Genesis, Inc.
Connecting Raw Points with
Lines for Slope Analysis
5       5      5        1        7       7       7       7         7        7

1       1       1       1        5       5       5       5         5        7

5       5       5       1       5        7       7       7         5       7

5       9       5       7        5       7       9       7         5        7

5       5       5       1        5       7       7       7         5       7

1       1       1       1        5       5       5       5         5        7

5       5       5       1       1        1       1       1         1       1

7       7       7       1        5       5       5       5         5        5

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques       Terra Genesis, Inc.
Surface Values with Slope = 0:

5        5        5        1          7        7        7        7      7       7

1        1         1        1        5        5        5        5       5       7

5        5        5         1        5        7        7        7       5       7

5        9         5        7        5        7        9        7       5       7

5        5        5         1        5        7        7        7       5       7

1        1         1        1        5        5        5         5      5       7

5        5        5         1        1        1        1        1       1       1

7        7         7        1        5        5        5        5       5       5

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Extracting and Vectorizing
Contours:

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Contour Development,
Slope = 0:

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Connecting Slope < 0:

5        5       5         1         7        7        7        7       7       7

1        1        1        1         5        5        5        5      5        7

5        5        5        1        5         7        7        7      5       7

5        9        5        7         5        7        9        7      5        7

5        5        5        1         5        7        7        7      5        7

1        1        1         1        5        5        5        5       5       7

5        5        5        1        1         1        1        1      1       1

7        7        7        1         5        5        5        5      5        5

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Flow Direction/Slope Vector Field

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Flow Direction:

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
point
together
stream bed

point apart
water shed

point in line
water flow

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Stream Bed Inflection Points:

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.3. Surface Analysis
What is color/value stretching?

How is slope defined?

How are contour lines developed by a computer from a
surface model?

What is the mathematical restriction of a surface
model?

What may be said about interpolation in a surface
model?

Describe a stream and a water shed boundary in terms
of slope arrows.

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.4. USGS Digital Data

    DEM - Digital Elevation Model
    DOQ - Digital Orthophoto Quadrangle combine
digital photography with DEMs
    DRG - Digital Raster Graph is a scanned and
    DLG - Digital Line Graphs are linear
transportation ,boundary and hydrographic
features
    http://edcwww.cr.usgs.gov/doc/edchome/ndcdb/
ndcdb.html
    http://edcwww.cr.usgs.gov/webglis

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DEM - Digital Elevation Model

    Digital representations of cartographic
information consisting of an array of regularly
spaced elevations
    Created from digitized or scanned cartographic
map overlays
    Contour lines are scanned into digital form
    Mathematical algorithms parse out and
interpolate ‘postings’ and a set interval

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DEM Display Techniques

95 1689 1692 1699 1697 1697 1704 1707 1709 1712 1721 1726 1729 1729
1728 1727 1726 1726 1726 1726 1726 1727 1726 1725 1723 1720 1717
1709 1707 1713 1714 1713 1706 1700 1690 1683 1682 1682 1682 1684 16
80 1692 1692 1693 1691 1700 1705 1712 1713 1706 1695 1677 1674 1670
1670 1670 1671 1674 1677 1679 1680 1683 1683 1685 1688 1690 1694
1695 1698 1701 1703 1707 1712 1712 1718 1718 1721 1719 1719 1719 17
19 1719 1719 1719 1719 1719 1719 1719 1719 1719 1718 1718 1716 1715
1714 1713 1712 1710 1707 1706 1703 1707 1706 1707 1707 1707 1707
1708 1708 1708 1708 1708 1707 1708 1704 1702 1701 1701 1701 1701 17
00 1700 1701 1701 1704 1707 1708 1708 1707 1707 1707 1707 1707 1707
1707 1707 1707 1707 1705 1705 1703 1702 1696 1691

1 2 463 1 0.510420000000088D+06 0.462183000000000D+07 0.000
000000000000D+00 0.156200000000000D+04 0.173000000000000D+04 1686 1686 16
87 1686 1685 1685 1685 1686 1684 1686 1686 1687 1687 1688 1685 1679
1677 1673 1676 1677 1681 1683 1686 1689 1690 1693 1696 1700 1706
1713 1715 1722 1720 1719 1718 1717 1718 1720 1714 1710 1706 1705 17
02 1700 1696 1690 1688 1689 1690 1692 1694 1695 1700 1703 1708 1717
1725 1726 1725 1721 1714 1710 1708 1709 1712 1708 1703 1697 1695
1694 1695 1688 1690 1697 1697 1701 1706 1713 1712 1711 1716 1726 17
30 1730 1729 1728 1727 1727 1727 1727 1727 1728 1727 1725 1724 1723
1720 1715 1714 1722 1721 1717 1710 1702 1691 1685 1682 1681 1680
1680 1677 1682 1692 1687 1675 1683 1687 1706 1706 1704 1690 1676 16
72 1669 1670 1670 1671 1671 1675 1676 1679 1681 1681 1684 1688 1689

Raw File
1692 1693 1695 1699 1700 1701 1704 1711 1718 1721    Gray Scale              Shaded Relief

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques    Terra Genesis, Inc.
STORM KING MOUNTAIN PERSPECTIVE
- VIEW FROM SOUTH LOOKING NORTH

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DEM Applications

    Sediment transport models
    Slope, aspect, and habitat
models
    Vegetative analysis
    Land surface
characteristics
    Water shed analysis
    Animal vs. human conflict
    Fire prevention
    Erosion control

Old Faithful, WY

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Level 1 Before                     Level 1 After                     Level 2 After

Mount St. Helens
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Laser Distance and Ranging
(LIDAR)

Digital Orthophoto:
• 6 inch pixel
• 1 m horizontal

Digital Elevation Model:
• 2.5 meter horizontal
• 15 cm vertical

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Digital Orthophoto Quarter

   A digital image of an aerial
photograph in \which
displacements caused by
terrain relief and camera tilts
have been removed
   Created from digitally-
corrected, scanned aerial
photographs
   Combine photograph image
characteristics with map
geometric qualities

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DOQQ Components
Digital Orthophoto
Digitally scanned aerial photograph

Digital Elevation Model

Camera Position/Orientation Data

Automated Rectification Process

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DOQQ Characteristics

•   Black and White or Color-infrared
•   3.75-minute X 3.75-minute
•   NAD 83 / UTM Projection
•   Pixel represents 1 square meter
•   50 - 300 meter overedge
•   Header information + binary data

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Using the DOQ as a revision
tool, it is easy to see the
amount of change displayed by

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DRG - Digital Raster Graph

    Created by scanning a USGS topographic map at
250 dpi or finer
    Georeferenced to Earth’s surface in UTM
    Used to collect/revise other digital data
    Greticuel screening is removed
    Color quantization to reduce the number of
colors using RGB model
    Converted to Tagged Image File Format (TIFF)
    Final file size 5-15 MB

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DRG of Grand Tetons

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Leaking Underground
Storage Tanks

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DRG files merged with DEM
Drainage basin area clipped out

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DRG merged with DOQ

Used for:
Resource management
Data collection/revision
Environmental assessment

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
DLG - Digital Line Graph

    Digital vector representations of cartographic
information
    Derived from hard copy cartographic sources
materials, aerial photographs, or raster graphic
products
    Contains a full range of attribute codes
    7.5 minute boundaries, PLSS, transportation,
hydrography

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
Hydrography

Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.
2.4. USGS Digital Data
What sources are currently used for DEM products?
How will this change in the future?

How is a DOQ produced?

If you needed a background for a GIS model, what
might you consider using?

What does “ortho” mean?

If you needed to develop a low-cost GIS from scratch,
what might you consider using?
Intermediate Modeling for GIS: A Technical Primer for Advanced Techniques   Terra Genesis, Inc.

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