Creating a Buffer - MapInfo_Pro - 2023

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.
   Note: 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.
2. On the SPATIAL tab, in the Edit group, 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 Pro 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.
     Note: Creating a buffer is time consuming. The higher the smoothness (more segments), the longer it takes to create a buffer.
   • One buffer of all objects - Select this option to create one buffer for all of the objects you have selected. For example, if you are buffering Pennsylvania, New York and New Hampshire, one buffer will be created for all three of these objects.
   • One buffer for each object - Select this option to create one buffer for each object you have selected. For example, if you are buffering Pennsylvania, New York and New Hampshire, each object will have a separate buffer.
   • Buffer Width Distance using Spherical - Select this option if you want the buffer to take into account the curvature of the Earth. Using this method, MapInfo Pro converts the data to Latitude/Longitude and then creates a mathematical calculation of the buffer. You cannot use this method for non-Earth projections.
   • Buffer Width Distance using Cartesian - Select this option if you want the buffer to be calculated as if the map is on a flat plane. Cartesian coordinates are a pair of numbers, (x, y), defining the position of a point in a two-dimensional space by its perpendicular projection onto two axes which are at right angles to each other. If you are using a Latitude/Longitude projection, this option is disabled.
4. When you have completed your entries and selections in this dialog box, click the Next button. The standard Data Aggregation dialog box displays.
   Note: If the editable layer is the Cosmetic layer, the Data Aggregation dialog box will not display because there is no data in the layer to aggregate. The OK button displays in place of the Next button. Click OK to begin the buffer operation.
5. Highlight each of the columns to complete the fields in this dialog box.
   • No Change - Select this option to keep the value for the selected column in the target row unchanged. This option only displays when you combine objects into a target object.
   • Blank - Select this option to store blank values in the selected column(s). To store blank values in all displayed columns, select the No Data check box. Only choose the Blank option to blank out individual columns.
   • Value - Select this option to store the value that displays in the edit field in the new row. When you select this option, enter an appropriate value in the field.
   • No Data - Check this check box if you want no data aggregated to any column.
6. After setting the appropriate data aggregation parameters, click OK. MapInfo Pro calculates the buffer according to the parameters you set and creates the new objects in the editable layer. The original objects remain unchanged. Once MapInfo Pro has created the buffer region, it puts it in the editable layer.
   
   

   

   
   

When using this feature remember that the greater the value in the Smoothness field, the greater the demands you are placing on your system's RAM, on disk space, and on processing power. Please take these points into consideration to avoid out of memory issues. If you do encounter memory issues however, consider one of the following:

• Use the thinning operations to reduce the resolution of your data or
• Increasing your machine's RAM may allow for more complex object processing

Table Variables

If the table containing the selected table and the editable table are either the same table, or contain the exact same table structure (same number of columns with each column in both tables having the same name and data type), then the Sum and Average radio buttons do not display. The data is taken from the current selection, and the results are placed in the editable layer.

If the table containing the selection objects and the editable table are different, and the table structures are different, then the Sum and Average radio buttons are displayed. In this case, the data aggregation for the editable destination table column is initially blank, and you need to select the column from the input selection table to derive the data from.

Saving your Buffer as a New Layer

You can create a buffer and save it as a new table (layer) or as part of another layer in your map. This process is similar to the Voronoi process described in Saving your Voronoi Polygon as a New Layer. This process is also similar to the Combine Using Column process, except that there is no "Group By" functionality for buffers.

To create the buffer as a distinct layer:

1. To create a selection to buffer, select the object in the map. This step is not required if you want to buffer all objects in a particular table.
2. On the SPATIAL tab, in the Edit group, click Buffer Objects from the list to open the Table Buffer dialog box.
3. Do one of the following:
   • To buffer the selected object, leave the Selection object selected in the Buffer objects in table drop-down list box.
   • To buffer objects from a particular table, select the table in the Buffer objects in table drop-down list box.
4. Select the type of table you want to place the buffer into from the Store results in Table drop-down list box. Select one of the following:
   • New table - saves the buffer in a new table
   • <tablenames> - saves the buffer in one of the currently open tables

     After you make this selection, click Next to continue.

     Note: You cannot save a buffer to the Cosmetic Layer.
5. Do one of the following:
   • If you chose the New table option, go to Saving a Buffer to a New Table in the Help System.
   • If you chose <tablenames>, go to Saving a Buffer to an Existing Table.

Saving a Buffer to a New Table

You can create a buffer and save it as a new table (layer) in your map. You must complete the instructions in Saving your Buffer as a New Layer before you begin this operation.

1. Use the New Table check boxes to indicate where you want the new buffer to display. You can click more than one check box.

   Open New Browser - Select to display the new buffer in a new Browser window only.

   Open New Mapper - Select to display the new buffer in a new Map window.

   Add to Current Mapper - Select to display the new buffer in the current Map window.

2. Choose the table structure for the new table, using only one of these options:

   Create New - Click this check box to specify a new table structure and create the new fields in the New Table Structure dialog box.

   Use Table - Click this check box to create the new table structure based on the fields in an existing table. You can base your new table structure on any open table.

3. Click Create to open the New Table Structure dialog box.

   If you selected Create New in the last step, the New Table Structure dialog box displays no fields and you need to add the fields you need.

   
   

   

   
   

   Click the Projection button to set the table's projection. For more about this, see Coordinate Systems, Projections, and their Parameters.

4. Click the Add Field button and enter the field name, select the field type, and enter the field width for each new field until your table structure is complete.
5. Click Create to create the table and display the buffer. The Create New Table dialog box opens prompting you to save the name of the new table.
6. Select the directory for this table and type the name of the new table in the File Name field. Click Save.

Saving a Buffer to an Existing Table

You can create a buffer and save it as a layer in an existing table in your map. You must complete the instructions in Saving your Buffer as a New Layer before you begin this operation.

To save a buffer to a table:

1. When you choose to store the table results in the existing table, the Data Aggregation dialog box opens.
   1. Click a field from the Destination list.
   2. Specify the data aggregation method in the Aggregation Method panel.
      Note: If you selected tables with disparate values, there may be additional fields in this dialog box. You need to reconcile these table values using this dialog box.
2. In the Data Aggregation dialog box, click a field and specify an aggregation method:

   Blank - Click this radio button to indicate that this field should remain blank.

   Value - Click this radio button to indicate that this field should contain a specific value or should retain its existing value. If the field should contain a specific value, enter that value into the Value field.

   Sum - Click this radio button to add the field values from the original objects to create a field total for the field in the new column. (Applies to numeric fields only.)

   Average- Click this radio button to average the field values from the original objects. (Applies to numeric fields only.)

   Weighted by - Click this radio button to give more weight to one value over another when averaging. You can choose a numeric field in your table as the weighting factor or choose area (where the weighted average is based on the relative geographic area of the regions to be combined). Applies to numeric fields only.

3. To add no data to the existing table, select the No Data check box. This disables the Blank and Value radio buttons.
4. After you have completed these selections and entries, click OK.
5. The Buffer Objects dialog displays. From here the process is the same as described in Creating a Buffer.

Buffer Radius

The buffer radius determines the dimensions of the buffer region. For example, if you want to create a region that covers an area one mile on either side of a freeway, set your buffer radius to 1 mile. If you choose to use a field from the table or an expression, MapInfo Pro will calculate the radius of the buffer based on that value.

You can set the radius to be a constant value or you can choose a data value from the table to be used as the radius. For example, to create buffers around major cities that reflect the size of their population, choose the population field as the value.

You can go even further to calculate the buffer radius using an expression. For instance, you want to create buffers around cities showing the population density. Since you do not have a field containing population density, you will need to write an expression that can calculate density from population and area. This is no different than writing an expression for thematic mapping or query selection.

Buffering - Setting the Number of Segments per Circle

The number of segments per circle determines the level of detail in the buffer region. The more segments per circle, the higher the level of detail. The default level is 12 segments per circle.

Buffer Width Distance

MapInfo Pro's buffering feature calculates the buffer width to create a buffer that is some measured distance from the outline of the object. This distance is calculated using either the Spherical or Cartesian method.

Spherical calculations measure distance according to the curved surface of the Earth. This means that the distance from the boundary of the original object to the boundary of the new buffered object may vary from node to node.

Cartesian calculations measure distance on data that has been projected onto a flat, X-Y plane. This produces buffers that are exact in width, as long as the data is not in a Latitude/Longitude projection.

The availability of the Spherical and Cartesian buttons depends on the type of calculation that is appropriate to the table's projection. The Cartesian button will not be available if the table is in a Latitude/Longitude projection. Conversely, the Spherical button will not be available if the table is in a Non-Earth projection.