Pitney Bowes MapInfo Professional - Manual (Page 290)

Buffering Your Data
If you would like to search for all underground cable wires that are buried within 440 yards of Interstate
490 or you would like to contact all families with pre-school age children who live within five miles of a
proposed school district, buffering is the tool for you.
Understanding Buffers
A buffer is a region that surrounds a line object, another region, symbol, or any other object in a Map
window. For example, you can create a buffer region that surrounds Interstate 90 by 440 yards on either
side. You can create a buffer region that surrounds the proposed school district by five miles on all
borders. Both the 440 yards and five miles are their respective regions' buffer radii. The buffer table is
then joined to data associated with the original buffered objects.
The maximum buffer resolution is 500 segments per circle. This affects the entry you can make
in the Smoothness field of the Buffer Objects dialog box. Note:
Creating a Buffer
To buffer objects:
1. Select the objects that you want to buffer. Make sure there is an editable layer in the Map window.
The output buffered objects will be placed in that layer.
There are certain table variables that you need to be aware of that will determine the
aggregation method used in joining the table of buffers to data associated with the original
objects. See
Table Variables for this information.
Note:
2. On the Objects menu, click Buffer. The Buffer Objects dialog box displays.
3. Select appropriate buffer radius, segments per circle, distance type calculation to use, and buffer
method as described.
• Radius - The radius is the width of the buffer you want to create around the object you selected.
The Value and the From Column radio buttons give you different ways to specify that width.
• Value - Type a value into this field if the radius of the buffer you want to create is a specific distance.
Examples might include 10 feet, 20 kilometers, 50 chains.
• From Column - Select this radio button if the buffer you want to create is specified in a particular
column or is to be calculated by an expression. Then select the column or choose Expression
from the drop-down list.
• If you select Expression, the Expression dialog box displays. Specify the expression you want
MapInfo Professional to use to calculate the buffer radius and click OK to return to the Buffer
Objects dialog box.
• Units - Select the units for the buffer from this drop-down list. Options include: inches, links, feet,
US Survey feet, yards, rods, chains, miles, nautical miles, millimeters, centimeters, meters,
kilometers.
• Smoothness - Type the number of segments per circle that determines the resolution of the curves
in the buffer polygon. You can enter a number between 3 and 100. The default value is 12 segments
per circle. If making adjustments, a value of 24 yields good results.
• The more segments you enter, the smoother the curve. The fewer segments, the more jagged the
curve. More segments produce a smoother curve; fewer segments make a more jagged curve.
Creating a buffer is time consuming. The higher the smoothness (more segments), the
longer it takes to create a buffer. Note:
MapInfo Professional 12.5 290
Buffering Your Data