Editing vector layers in QGIS

For this exercise please use QGIS version 2.18.

Various vector layers and tables (OGR, SpatiaLite, PostGIS, MSSQL Spatial or Oracle Spatial) can be edited in QGIS.  Before you start a editing session in QGIS, make sure you set the right snapping options (Snapping Tolerance and Search Radius). In QGIS you can find these options in Settings > Options > Digitizing or in Settings > Snapping Options. This will optimize the editing process of the layers.

Make sure you check the Default snap mode to > Vertex and segment.

For Default snapping tolerance and Search radius for vertex edits select a value and from the drop down menu set the values to map units. After you set these parameters you can proceed with your edit process.

In order to start editing a vector layer the next steps are recommended:

• Select the vector you wish to edit by clicking it.
• Go to Toggle Editing and start a new edit session.

• Activate the Advanced Digitizing toolbar. Go to View > Toolbars > Advanced Digitizing Toolbar. The new toolbar is opened.

Using the basic editing tools you can perform operations like:

Icon	Purpose	Icon	Purpose
	Current edits		Toggle editing
	Add Feature: Capture Point		Add Feature: Capture Line
	Add Feature: Capture Polygon		Move Feature
	Add Circular String		Add Circular String By Radius
	Vertex tool		Delete Selected
	Cut Features		Copy Features
	Paste Features		Save layer edits

The Advanced digitizing and editing tools enhance the capabilities of QGIS performing operations lik

Icon	Purpose	Icon	Purpose
	Enable Advanced Digitizing Tools		Enable Tracing
	Undo		Redo
	Rotate Feature(s)		Simplify Feature
	Add Ring		Add Part
	Fill Ring
	Delete Ring		Delete Part
	Offset Curve		Reshape Features
	Split Parts		Split Features
	Merge Attributes of Selected Features		Merge Selected Features
	Rotate Point Symbols		Offset Point Symbols

Lets try a few of these tools and see how they work.

For example if we want to split an polygon (in our case an area represented by a protected area), after a certain limit (a administrative unit limit) we will proceed and use the Split Features tool along with Trace tool. The polygon will be split in 3 parts according to the next image.

Clicking on the Trace and Split Features buttons and having the snapping tolerance set we can proceed and split the polygon according to the administrative limits.

With the trace tool activated follow the administrative unit limit.

At the end you should have three separated polygons. Each polygon was split according to the administrative area.

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