Preprocessing: Creating a Data Dictionary
Source: GeoExplorer 3 System, 1999
First view the handout showing examples of different types of features and attributes,
then discuss with your partner the point, line, and area features that you would like to
survey on campus, preferably in the Pearce Courtyard. The project should have some
unifying theme, for example, condition of the physical plant (lights, sidewalks, parking
lots), an imaginary wetland (plant location, location and condition of recreational
paths, wetland area), or sources of soil erosion (bare spots, paths, large building
excavations). Think about the attributes and values that you could associate with
point, line, and areas.
After discussing examples of point, line, and attribute data, you will make a
reconnaissance of the Pearce courtyard to determine the point, line, and area
features, with attributes, that you will collect for this exercise. You have flexibility in
determining what features you will collect but you will need to have the point
feature in the “menu” format, the line feature in the “numeric” format, the
area feature in the “text” format, and create two features using the “date”
format.
1. To access the data dictionary routine open Pathfinder Office from the GPS section
of the Start Menu and click on the
“Data Dictionary Editor” icon located on the
left margin of the Pathfinder Office window. The “Untitled-Data Dictionary Editor”
window opens. Before clicking on “New Feature” on the bottom left of the screen,
give the dictionary a name in the name field, perhaps, “Campus Project.”
2. After clicking on “New Feature”
A “New Feature” window
appears. Making sure that the “point” feature classification is selected under “Feature
Classification” box, type the name of the point feature that you decided to survey on
campus. This action will create your selected point as a single, discrete geographic
feature to which you can assign attributes. The name of your point feature will appear
in the field when you are collecting points with a GPS unit. Hit “OK.”
1
3. Note that the new point feature you created now appears as a point feature
under the white “Features” column. You now
need to type attribute information concerning
the point feature. What are examples of
attributes? Perhaps pH, color, soil texture,
nitrogen content, length, width, soil horizon
depth, number of cancerous lesions. Making
sure you are still on the “Data Dictionary Editor”
window click on the “New Attribute” button.
A small “New Attribute
Type” window appears with various options. Select “Menu” and click “Add” A “New
Menu Attribute” window appears allowing you to specify feature attributes. Menus
are a convenient option to use in GPS data collection because you create a
predetermined list of attributes choices, saving you the bother of manually typing
each variable attribute.
4.. In the “New Menu
Attribute” window type
in your choice for
attribute name (ex.
color, or condition)
then click the “New”
button found on the
middle left of the
window.
A smaller
“New Attribute Value—
Menu Item” window
will appear. This is the
window where you
type the data range or
condition (poor, fair,
good,
excellent)
associated with your
attribute.
In
the
“Attribute Value” dialog
box, type in a value or
range of values that
you feel are reasonable
for the attribute variable in question. Assign a code value that can correspond to the
attribute value—this will make data collection easier out in the field. Click on the
“Add” button to attach the value to the attribute. Instantly another “New Attribute
Value—Menu Item” window appears. Type in the second and then third value for this
attribute. You will need a minimum of three separate values or value ranges for your
2
selected attribute. Check the default box for the attribute value you think will recur
most often. When you go out in the field you will collect a minimum of five
point features of the same type (for example, five lampposts)
5. When you have finished adding values, press “Cancel” to exit the “New Attribute
Value—Menu Item” menu, “Cancel” to exit the “New Menu Attribute” menu, and
“Cancel” to exit the “New Attribute Type” window. This will return you to the “Data
Dictionary Editor” window.
6. Using the directions provided above, create an attribute for a line feature that
requires a numeric value. Do not choose “Length” as an attribute feature as this
information can be directly derived from Pathfinder Office utilities. Sometimes, a job
requires exact values, for example, pH 7.23 or temperature 2.93ºC. Based on the
type of attribute you have chosen, choose an appropriate number of decimal places, a
minimum and maximum value, and a default value. Note: You will be graded on how
reasonable your choices are. When out in the field, capture at least three line
features of the same type (for example, three different sidewalks that would have
different attributes). Don’t, for example, assign a maximum value of 1,000,000 if
there is no way you would ever come across this large value during the normal course
of data collection.
7. Using the directions provided above, create an attribute for one area feature
that requires a text value. Most of the time you won’t use this option because it is
easier to collect attribute data in the menu mode. There are situations, however,
where a text value is warranted, like????
8. Using the directions
provided above, create
an attribute for a point,
line, OR area feature
that requires a date
attribute. This is useful
for inputting a “last
inspection
date”
attribute
recording
when
a
particular
feature
was
last
observed. The autogenerate option will
automatically fill the date inspected attribute with the current date. Clicking off the
“Auto Generate” options will allow for date information to be inputted manually.
Choose the “Day-Month-Year” format for displaying dates. Collect at least two
features in the date format. In what situations would manual inputting of date
information be necessary rather than auto generation of a date?
3
9. Once you have completed inputting features and their attributes, save the data
dictionary to your workspace giving it the name, “courtyard (initials for your team)”
For example, “courtyardmdsl” where md is the initials of the first team member, sl is
the initial of the second team member. Note that a .ddf extension appears. Save this
data dictionary in a safe place in both team members workspace.
10. Print out the data dictionary. Have a text version of a data dictionary is a
good way to review the attributes of the entire job.
What to turn in next week (one paper per team):
1. What situations exist where a text values are warranted for data
dictionaries? (2)
2. In what situations would manual inputting of date information be
necessary rather than auto generation of a date? (2)
3. Discuss the underlying theme for the data dictionary created. How do all
attributes “fit” into this theme? Suggest another theme with specific
examples of point, line, and area attributes (4)
4. Complete print out of data dictionary (4)
Distinguished
Analysis
Thoughtful
analysis,
especially on
question 3, no
conceptual
errors.
All
required
elements
present
and
additional
reference
(properly
referenced)
adds to the
report. (8)
Grammar and No grammar
appearance
errors,
very
neat. (2)
Proficient
One required
element
is
missing or one
conceptual
error. (6)
Basic
Two required
elements are
missing or two
conceptual
errors. (4)
Poor
More than two
required
elements are
missing
or
more
than
two
conceptual
errors. (2 or
less)
1
grammar Handwritten,
More than 3
error (1)
2-3 grammar grammar
errors. (0.5)
errors. (0)
4