|Easy Tip: An Introduction to Buffering |
| ||Buffering is a great tool for finding objects that are within a specified radius of another object. Examples include selecting objects within 500 metres of particular road or within a 2 km circle around a store. |
This article has been creating using the ribbon interface in the 64 bit versions of MapInfo Pro. The same capabilities are in the 32 bit versions of MapInfo Pro as well. Look in the Objects and Table menus for the equivalent commands.
Two menu commands for buffering
There are two different commands for creating buffers. They are found in the Edit group on the Spatial tab. These are Buffer Objects and Buffer Table.
The region objects that are created when buffering can be saved straight into the cosmetic layer or into an existing table by choosing the Buffer Objects command. It is important to note that whichever layer is editable will have the buffer saved into it.
The Buffer Table command provides the capability to create a new table to store the buffer objects. You can specify an entire table of objects to buffer without having to select them first.
The examples depicted below show some of the pristine ocean swimming pools that Sydney has to offer and are free for public use. The stores in surrounding suburbs sell various swimwear and equipment.
When you choose the Buffer Objects command, this is the dialog box that will appear.
In the map below, the smoothness value was chosen as 12. This is a low number and was chosen simply to highlight the effect that this value on the resulting object. A much larger number (maximum 500) can be chosen to create a smoother circle buffer.
The buffer below was saved into the cosmetic layer and the translucency of this layer changed by right-clicking on the layer and selecting Layer Properties.
It is often useful to save the buffer objects into one or more tables (instead of the Cosmetic layer) so that the translucency of the layers can be altered for visual purposes. This may be especially useful if multiple buffers are needed, each requiring different levels of translucency. You can also control the order of the layers and this has implications for selecting objects within the buffers.
This can be done by choosing Buffer > Buffer Table command. This is in the Edit group on the Spatial tab. This command takes you through the process of creating a new table before reaching the Buffer Objects dialog.
When multiple objects are selected to be buffered, you can choose to create One buffer for each object or One buffer of all objects.
Creating one buffer for each object results in separate regions objects. 3 region objects are created below and accordingly inserted into the table as 3 records. The colours of each object were changed to emphasise the differences. You can change the colours by double clicking in the buffer region and choosing a new region style.
Creating one buffer for all objects results in a single region object that spans the 3 swimming pools selected. See below.
To select objects within a buffer, you can use the Boundary Select tool. (This is in the Mini-toolbar or on the Spatial and Map tabs).
The Boundary Select tool will select the objects that are in the top-most layer, so clicking inside the buffer means that the objects in the Pools layer that are within this buffer region will be selected.
If we move the Stores layer up in layer control, then Boundary Select tools highlights all of the Stores that are within the buffer region.
Since a buffer is an object that is added as a new record to your table, this record will have the same fields as determined by the table structure.
Select 'Value' and this will fill in the same data from the object that is being buffered. Select 'Blank' for individual fields and this will result in a blank cells for these fields. 'No Data' creates a record with no data in any field.
Buffering has a large number of potential uses. Consider it whenever you have a requirement to analyse of some objects on your map are within a certain proximity to other objects.
You can buffer any sort of map objects. Here are some examples.
What about the 32 bit version?
- Buffer a fibre optic cable to find homes near the cable for which telephony and Internet services can be provided.
- Buffer a preservation area to determine areas where construction may or may not be allowed.
- Buffer a set of potential store locations as a basis to compare them.
Once again, the buffering capabilities are also in the 32 bit versions of MapInfo Pro. Look in the Objects menu for the Buffer command and in the Table menu for the Buffer Table command.
Article written by John Drummond, Associate Software Support Analyst
John enjoys hearing about the new ways that MapInfo Pro is being used in diverse industries. When not at work, John can be found in the Narrabeen rockpool or just outside surfing those gnarly left-handers.