Structures for Storing Geographic Data - Introducing Geographic Information Systems with ArcGIS - page 272

3. From [___]IGIS-Arc\Other_Data, use the operating system to copy the file Foozit_Court_Lines.txt
to the folder
___IGIS-Arc_ YourInitials \TextToFeature.
4. Use the Create Feature From Text File tool (remember: it's in the Samples toolbox) to make a
feature class named Foozit_Court_Lines in the feature dataset State_Athletics, using Foozit_
Court_Lines.txt. Examine the feature class with ArcCatalog.
5. Refer to Figure 4-21. How many polygons are there? ____. Compare the Figure with the
on-screen representation. Notice that three polygons are missing. Determine what text is
missing from Foozit_Court_Lines.txt that is causing the omissions.
6. Using a text editor (not a word processor), correct Foozit_Court_Lines.txt. Number the new
polygons 901, 902, and 903.
Save the file as Foozit_Court_Lines_Fixed.txt.
7. In ArcCatalog delete the feature class named Foozit_Court_Lines. Then remake it with the
repaired Foozit_Court_Lines_Fixed.txt. If the feature class Foozit_Court still isn't right, repeat
the above steps until it is satisfactory.
8. Create a polygon feature class named Foozit_Court_Polygons, using Foozit_Court_Lines as
input and the procedure you learned in Exercise 4-4. Check out Foozit_Court_Polygons with
ArcCatalog.
9. Start ArcMap. Add Foozit_Court_Polygons. Right click the T/C entry and click on label features.
You get some strange numbers, which I explain later. Instead let's use ArcMap's labeling
capabilities to label each polygon with the object identifier (OBJECTID). 9 Use Properties, Labels,
then fix up the Label Field.
10. Print Foozit_Court_Polygons. Now on the paper printout, label each polygon with its Shape_Area.
What is the indicated area of the largest polygon(s)? _________ Given the original definition
of the Foozit court and the locations of its vertices, what is the actual area of the largest
polygon(s)? ______________ Depending on the version of the software you are using, the
indicated values may not be exactly correct. Where you would expect to see 4.000000 you
might instead see something like 3.999984. Why? An explanation will be found in Exercise 4-7.
Exercise 4-7 (Exploration)
Understanding Some Things That Don't Look Right
1. Start ArcMap with a Blank Map. In
___IGIS-Arc_ YourInitials \Trivial_GIS_Datasets\FEAT_NUM
9 With a file geodatabase or personal geodatabase feature class the object identifier is OBJECTID; in a shapefile it is FID.
Why the differences? Because different pieces of the software were developed at different times and used different,
already written computer code.