Using the intersect geoprocessing tool in qgis

GO TO THE DEMO VIDEO PAGE AND CLICK ON THE LINK TO WATCH A

YOUTUBE VIDEO DEMO

Task
The demo will use two line feature layers- Major roads and Rail line to show the practical application of using the Intersect geoprocessing tool for identifying suitable areas along a rail line that would suitable to build rail crossings, rail to bus platforms and rail crossing signs.

Note

The buffers are for demonstration purposes alone, it may not be necessary to use buffers to explain use of the intersect tool.

Steps
- Placing a 0.0055dd buffer around the Major roads.This buffer distance represents the right of way along both sides of the major road.
-Placing a 0.0055 buffer around the Rail line.This buffer distance represents the right of way along both sides of the rail line.
- Intersect the two buffers to delineate the suitable sites along the Rail line.

Procedure DOUBLE CLICK ON THE IMAGES TO GET A CLEARER RESOLUTION 

Placing the Rail line and Major roads Buffers
The layers (red boxed) to process are the Rail line and the Major roads. Go to Vector > Geoprocessing tools > Buffers

A Buffer dialog box will pop up. Fill the details and use a buffer distance of 0.0055dd. In this dialog box, the buffer for the Major road is processed.

A new polygon layer MajorroadBuffer is added to the Layers window. A Buffer is placed around the Major roads layer.

Follow the same process for the Rail line layer. Observe that a new polygon layer- RaillineBuffer is added on to the Layer window.

To carry out the Intersect, Go to Vector > Geoprocessing tools > Intersect.

In the Intersect dialog box, fill in the buffer polygon layers- Rail line and Major roads. Give a name to the output shapefile-IntersectRoadRail.

The new shapefile is added after the processing. Observe that the resultant polygon represents the areas  along the Rail line where the Major roads intersect. The IntersectRoadRail represent the zones along the Rail line that would suitable to build rail crossings, rail to bus platforms and rail crossing signs

Annotation describing the suitable zones.