The Time Dimension - Introducing Geographic Information Systems with ArcGIS - page 569

The Time
Dimension

STEP-BY-STEP

Let's run through a quick example of how files of the same variety of data, taken at different times, might
be compared. Just as an example of one way of doing the comparison, we'll make use of the topology tool
available to us in geodatabase feature data sets. We'll use the buffer tool as well. For a second example,
we use the ArcMap Time Slider to look at the history of road repaving over several years.

Suppose that we are interested in knowing what new streets were built in a city in the United States over
approximately a decade. We have available a feature data set derived from the 1994 TIGER/Line files
from the 1990 census. We also have more current files: roads from the 2000 census. Suppose that we place
both files in a personal geodatabase's feature data set. Then, we could make a display showing both files.
There would, of course, be a great amount of overlap. We can identify that overlap using topology. If we
could then delete the streets that are (almost) coincident, we would be able to see the new streets that
were added. You do that in the following project.

Exercise 9-2 (Project)

Looking at Infrastructure Changes Occurring over Time

1. Start ArcCatalog. Copy the folder

[___] IGIS-Arc\Historical_Data

to your

___ IGIS-Arc_ YourInitials folder.

2. Create a folder connection to this new Historical_Data folder.

3. Inside the Historical_Data folder you will find the Geodatabase Roads.mdb. It contains the feature
data set Lexington_SP_North_83_Feet. Within that are the feature classes Lex_Roads_1994 and
Lex_Roads_2002. Make sure the Catalog Tree is showing (Windows > Catalog Tree).

4. Highlight the feature dataset name Lexington_SP_North_83_Feet. Using Ctrl-C and Ctrl-V, make
a copy of it in Roads.mdb. Make a second copy, also in Roads.mdb. Rename the copies Lex_