Lab 1: Digital Terrain Data Models
Due by October 8
before class.
This lab has three separate tasks that will let you explore different digital terrain data models. You will download a DEM from an Internet website. Task 2 involves the use of points and a DEM to learn how ArcGIS handles 3D objects. In Task 3, you will convert a DEM to a TIN data model. The exercise will be done using ArcGIS. This is your opportunity to explore the software and to get acquainted with the interface. Use the help system to learn about the different software options and functionality. Spend some time browsing the websites that you visit in this lab. Type the answers to all questions at the end of each task, attach your map, and submit them to the instructor by the due date.
Before you start the first lab, you need to know where to save your lab data. You are only allowed to put data in the C:\Users folder on the computers in CH469 or CH475. You can use your odin ID or your name to create a working folder in C:\Users so that your data won’t get mixed with other students’. If you want to access your working folder from other computers on campus, please follow the instructions on this page. Then create a folder for lab1.
Task 1 guides you through the process of downloading a DEM and converting it to a grid. The DEM is in SDTS format, and the SDTS files are in the TAR.GZ zipped format.
You will
use the DEM you just created to assign elevation data to a RLIS fire station
layer.
1.
Add
I:\Students\data\GIS\RLIS\2008_Aug\ESRISHAPEFILES\PLACES\fire_sta.lyr to the
same data frame you created in Task1. Click the selection tab of the left panel
of ArcMap, check the fire stations layer and uncheck all other layers. Use the
Select Features tool to select only the fire stations within the extent of the
DEM.
2.
Right-click on the fire_sta layer
and select Data/Export Data. Check the data frame option button so that the
output uses the same coordinate system as that of the data frame (i.e., DEM’s
coordinate system. Type in the output shapefile’s
path and name (e.g., C:\users\odin\firestations.shp) and click OK to finish the
feature extraction process. Make sure you have read/write access privilege to
the path you specified in the output field. When done, open the attribute table
of firestations and make sure it has 13 records.
(Alternative method: This method requires the use of “project” tool to reproject the fire station layer to the projection of the
DEM. Click Show/Hide ArcToolbox Windows to open the ArcToolbox window in ArcMap.
Double-click the Select tool in the Analysis Tools/Extract toolset. Click on
the down arrow of the input features field and select fire_sta
from the dropdown list. Set output feature class as firestation
shapefile in your lab1 folder. Click OK to continue.
When using the PROJECT tool in Arctoolbox, you need
to specify two transformation methods: NAD_1983_To_HARN_WA_OR and then
NAD_1927_To_NAD_1983_6.)
3.
Start ArcScene. Add firestations and pdxdem to the
data frame in ArcScene. (Do you see a flat map of DEM
and points that you can spin around when you drag the cursor?) Double-click on pdxdem layer to open the layer properties window. Click on
the
4.
Open the ArcToolBox
window in ArcScene and make sure that the Spatial
Analyst extension is enabled. Double-click the Extract Values to Points tool in
the Spatial Analyst Tools/Extraction toolset. Select firestations
as the input point feature and pdxdem as the input
raster. Set output as firest_z shapefile
in your lab1 folder. Click OK to continue. Open and compare the attribute
tables of firestations and firest_z.
Answer Question 1 below now.
5.
Go to View/Toolbars on
the ArcScene pulldown menu
and open the 3D Analyst toolbar. Select “Features to 3D” from the 3D
Analyst/Convert menu. Set firest_z as the input
feature and use “RASTERVALU” as the input feature attribute option. Save the
output as firest_3d in your lab1 folder.
6.
The firest_3d layer is
automatically added to the data frame. Is it displayed as a flat map of points?
Double-click on the firest_3d layer. Click on the
7.
Double-click the Add
XY coordinates tool in the Data Management Tools/Features toolset in ArcToolBox. Set firestations as
input features and click OK. Use the same tool to process the firest_3d layer. Open
and compare the attribute tables of firestations and firest_3d. Answer Question 3 below now.
8.
(Optional step) Repeat step 5 and use the raster
or TIN surface option (specify pdxdem as the raster)
to convert firestations to a new 3D shapefile. What happened? Explain.
1.
Double-click the
Raster to TIN tool in the 3D Analyst Tools/Conversion toolset. Select pdxdem for the input raster, specify pdxtin
for the output TIN, and change the Z Tolerance value to 10. Click OK to run the
command.
2.
You can view pdxtin in a variety of ways in ArcMap
or ArcScene. In ArcMap,
select Properties from the context menu (i.e., right-click menu) of pdxtin. Click the Symbology tab.
Click the Add button below the Show frame. An Add Renderer scroll list appears
with choices related to the display of edges, faces, or nodes that make up pdxtin. Click "Faces with the same symbol" in the
list, click Add, and click Dismiss. Uncheck all the boxes in the Show frame
except Faces. Make sure that the box to show hillshade
illumination effect in 2-D display is checked. Click OK on the Layer Properties
dialog. With its faces in the same symbol, pdxtin can
be used as a background in the same way as a shaded relief map for displaying
map features such as streams, vegetation, and so on.
1.
The default Z
tolerance in the Convert Raster to TIN dialog is 125.4. What happens when you
change the tolerance to 10?
2.
How many nodes and triangles are in pdxtin?
3.
Make a map showing the TINs you created with
different Z tolerance values.