Masayoshi Oka mokagsd.harvard.edu

1
GIS Workshop Session 3
Introduction to Geographic Modeling

• Terrain Models
• Triangulated Irregular Network (TIN)
• Digital Elevation Models (DEM)
• Making Contours
• gsd dem tools
• GIS Data into CAD
• CAD Data into GIS
• ArcScene
• 3D Visualization

Masayoshi Oka (moka_at_gsd.harvard.edu)
2
Terrain Model
Basics Usually expressed in terms of the
elevation, slope, and orientation of a land
surface. Provides opportunities and challenges
of how and where various design interventions
will go. Provides a very flexible way of laying
a groundwork of the site. Ability to interpolate
between indicators of elevation and landform to
understand the entire surface by creating a
Triangulated Irregular Network (TIN). Can be
used to generate contours with any intervals for
the purpose of geographic display and/or for
laser cutting.
Source http//www.gsd.harvard.edu/gis/manual/cont
ours/index.htm
3
Terrain Model
Benefit of a Terrain Model??
Source http//www.gsd.harvard.edu/gis/manual/cont
ours/index.htm
4
Terrain Model
Benefit of a Terrain Model
Source http//www.gsd.harvard.edu/gis/manual/cont
ours/index.htm
5
Terrain Model
Triangulated Irregular Network (TIN) A form of
vector based digital geographic data and a
digital means to represent surface
morphology. Constructed by triangulating a set
of vertices (points). The vertices are connected
with a series of edges to form a network of
triangles.
Source http//webhelp.esri.com/arcgisdesktop/9.2/
index.cfm?TopicNameAbout_TIN_surfaces
6
Terrain Model
Triangulated Irregular Network (TIN) TIN models
are less widely available than raster surface
models and tend to be more expensive to build and
process. The cost of obtaining good source data
can be high, and processing TINs tends to be less
efficient than processing raster data because of
the complex data structure. TINs are typically
used for high-precision modeling of smaller area,
such as in engineering applications. Due to the
ability of calculating planimetric area, surface
area, and volume
More mass points breaklines.
Source http//webhelp.esri.com/arcgisdesktop/9.2/
index.cfm?TopicNameAbout_TIN_surfaces
7
Terrain Model
Digital Elevation Model (DEM) Also known as a
Digital Terrain Model (DTM). Usually used in the
GIS platform. It is a raster version of
elevation value that represent the world as
regular arrangements of pixels (cells). The
representation of continuous elevation values
over a topographic surface by a regular array of
z-values. National Elevation Dataset National
Land Cover Characterization Dataset (NLCD) A
complete seamless coverage of DEM and Land
Cover. US Geological Survey (USGS)
http//seamless.usgs.gov/index.php
Source http//www.gsd.harvard.edu/gis/manual/dem/
index.htm
8
Terrain Model
Spatial Analyst Extension
Derivatives of Elevation
Source http//www.gsd.harvard.edu/gis/manual/dem/
index.htm
9
GIS Data into CAD
ArcToolbox gt Conversion Tools gt To CAD Tools in
the To CAD toolset convert geodatabase features
to native CAD formats. Add CAD Fields Adds
fields containing CAD properties. The fields are
recognized by the Export to CAD tool. Create CAD
Xdata Creates a table. The table is recognized by
the Export to CAD tool as AutoCAD Extended Entity
Data. Export to CAD Creates CAD drawings in their
native format (DGN, DWG, or DXF). Set CAD
Alias Renames fields with CAD aliases.
Source http//webhelp.esri.com/arcgisdesktop/9.2/
index.cfm?TopicNameAn_overview_of_the_To_CAD_tool
set
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GIS Data into CAD
1 Select an area of interest in ArcMap. a whole
city coverage of contours or building footprints
as a DXF file is too big 2 Export the layer of
interest layer-by-layer. follow the steps below
to crop the layer
Right-Click on the Layer
Source http//www.gsd.harvard.edu/gis/manual/cad/
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GIS Data into CAD
3 Locate the Conversion Tools toolbox in the
ArcToolbox 4 Use the Add CAD Fields wizard to
contain a CAD Properties. Simply choose a GIS
data that consist contour lines of interest.
Source http//www.gsd.harvard.edu/gis/manual/cad/
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GIS Data into CAD
5 Verify that the Attribute Table have more
columns.
Source http//www.gsd.harvard.edu/gis/manual/cad/
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GIS Data into CAD
6 Use the Field Calculator to assign an
elevation.
Set the value for the Elevation attribute to
equal the value found in the GIS contour
data. in this case ELEV_M
Source http//www.gsd.harvard.edu/gis/manual/cad/
14
GIS Data into CAD
7 Use the Export to CAD tool to create a DWG
file.
When renaming the file, remember to identify the
extension.
Source http//www.gsd.harvard.edu/gis/manual/cad/
15
CAD Data into GIS
Handling CAD Data Simply click on the standard
Add Data button and navigate to the directory in
which CAD data is stored. Choose the necessary
CAD data elements and click Add. CAD data will
appear in the Table of Contents just like any
other GIS layer. The CAD data will have the same
option of symbolization as GIS data, including
altering colors, line thicknesses, fill patters,
etc. The CAD data can be renamed and moved
around as GIS data.
Importing CAD data in the GIS is a simpler than
importing GIS data to CAD
Source http//www.gsd.harvard.edu/gis/manual/cad/