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OZGIS30.TUT
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OzCensus
========
The main display and analysis program is OzGIS.
A much simpler version of OzGIS is provided called OzCensus.
This version is suitable for simple mapping of Census type data and is
recommended for use while learning to use the system.
OzCensus has two or three menus and about twenty menu options while the full
OzGIS version has about fifty menus and a few hundred menu options.
When you want to do more advanced mapping use OzGIS!
Example map
-----------
The most common application is the display of data such as Census data as
coloured polygons. Here the processes necessary to display such data are
described.
You will start with a file of attribute data (such as population Census
data) and a file of digitised boundary data for mapping:
We will look at data for Far East Asia. There are two data files:
FEA-G.DAT are the digitised boundary data, and
FEA-A.DAT are the attribute data
First of all we have to enter the data so it is checked and written into
internal files:
type
cd \ozdemo
ozenter
1. select the option to enter standard format geographic files
give the input data file as fea-g
give the output geographic file as fea (or the default if you like)
2. select the option to enter an attribute file
give the input data file as fea-a
give the output attribute file as fea (or the default if you like)
3. type F10 to exit
Now the files can be displayed
type
ozcensus
choose the option to "DISPLAY A NEW MAP".
give the attribute file name as FEA (from above)
When asked for the geographic file name input "L". A list of the available
files will appear (type Enter or Esc to exit). Give the geographic file name as
FEA
The data are now processed, the map is displayed, and the next menu appears.
You now have a default map with legend and distribution diagram. The legend
has the numbers of zones in each class on the left and the class value ranges
to the right of the coloured boxes.
The map colours are defined in the default device file.
Now investigate some of the options:
Choose the option to display the next sequential attribute
If you only have 16 colours the system does not display the map until you
request regeneration. This enables several options to be changed before the
slow polygon drawing takes place.
If the map does not change type F3 to regenerate the map.
Select the option to select by number. Type 0 to get a list.
Type Esc to return to the question. Type in a number to select an attribute.
(type F3 to regenerate if necessary)
Select the option to change the number of classes.
change the number of classes to 10.
(type F3 to regenerate if necessary)
Select the option to change the quantisation method. Another menu will appear.
These options are very important as they enable the map to show the data in a
way relevant to the purpose of the analysis.
Choose QUANTILES and set the number of classes to 10 (deciles).
Type Esc to go back to the previous menu.
Choose the option to display statistics. Type return (or Esc) to remove the
window.
Choose the option to interrogate the map. This will enable the current values
for the displayed zones to be listed. A cursor will appear on the screen which
indicates the bottom left position. Place it using either the arrows (type
Enter to select the position) or the mouse (left button to select). A box
cursor then appears to select the other corner. All zones are listed where the
minimum bounding rectangle (MBR) intersects the selected window.
etc
Continue investigating options
Type F10 to exit.