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This article demonstrates how to create a buffer with a variable width extracted from an attribute. In this example, we have GPS Trace(point data) and vehicle speed to create geometry demonstrating traffic flow and some congestion points during the drive. Using an attribute value as the buffer size is useful in other areas such as the diameter of pipes, the width of roads, fire station/emergency services catchment areas, green belts zoning, etc.
This article helps you to understand the following:
The Bufferer transformer works with point, line and polygon features. Based on workflow when using line features, it may require to use Chopper to create line into individual points. For very complex objects the Generalizer can be used before buffering. When buffering Line features(as is), a LineJoiner and Snapper works great in various scenarios.
CSV Reader Parameter dialog
Before we begin our workflow, let’s visualize the data.
The next step is to create an attribute that store a variable value for buffer size.
(@Value(Speed)*4)
Bufferer transformer properties dialog
Next step is to convert individual polygons (see below) created in the previous step to a single polygon.
NOTE: Bufferer transformer has a Group By option which can be used to dissolve buffers together. In this case, since the size of the buffer is not equal (variable size), the option will not work.
For this, we are going to use the Dissolver transformer to dissolve buffer into areas. Add Dissolver transformer and connect "Buffered" output port to it. Use all the default settings.
Add an Inspector to Dissolver Area output port and view our final result in FME Data Inspector to verify that we can visualize some slow moving traffic spots during the drive. Complete workspace is located under the download section (buffer-from-attribute.fmwt)
NOTE: If required change Pen Color or Area Fill Color in FME Data Inspector to change Area and GPS point color.
The narrow areas on the map(highlighted) indicates congested areas.
The data used in this example originates from Open Street Map and is available under the Open Database License.
Buffering features for Spatial Relationship Analysis
Distance Measurements with the LengthCalculator
Determining Spatial Relationships
Build Road Lines from GPS Points (CSV to Shape)
Buffer On Left or Right Side Only
Point in Polygon Calculations with the PointOnAreaOverlayer
Shortest Route Calculations with the ShortestPathFinder
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