The Align Polygons task enables you to align polygon geometries from one layer to geometries from another layer. It has been designed to help in cleaning planning application data and aligning the outlines of planning records with OS Topography Layer i.e.: Master Map.
Align Polygons works by casting the geometry from the Layer onto the Stencil Layer and approximating which collection of polygons from the Stencil Layer closest represent the source geometry.
The configuration of this task, just like any other eVO Task, is preserved within a map. This task utilises layers contained within the map. This means that before setting up the task, you should prepare a map. Please see below the list of elements which have to be present within the map.
Layer - this is the layer which contains incorrect geometries. In most cases this layer stores planning application data. Data in this layer will be cleansed.
Stencil Layer - this is the source of correct geometries. In most cases it means the MasterMap Topography Area layer.
Auxiliary Layer - this is the auxiliary layer which stores approximated polygons. This layer must comprise of at least 3 columns: Primary Key, Geometry and a text field allowing for at least 2000 characters to be written. An example of Auxiliary Layer is shown below.
Offset Layer (optional) - this is the PAI offsets layer. This data is pre-processed by StatMap and delivered to the customer upon request free of charge.
When configuring the task you need to create an empty Flow and add the Align Polygons task to the Flow’s plan space (see Working with Flows and Tasks for general information on creating Flows and managing Tasks).
Assuming that you have all required layers available in your map, setting up the Align Polygons task is a very simple task. You need to provide each parameter by selecting a layer name or a field name from the drop down lists.
The only parameter which you need to enter manually, although it is by default set to 90%, is the Minimum Stencil Area Ratio. This parameter is responsible for deciding whether a polygon from the stencil layer will be included in the collection or not. If Stencil Layer polygon’s area contained within the checked polygon geometry is higher than this parameter, it will be included. If it’s lower, the Stencil Layer polygon will not be added to the collection. In most scenarios the default value of 90% delivers the best results.
Setting up a Flow
Open a map
Go to Flows tab
Click New button above the list of existing flows to add a New Flow to the list
Double click the New Flow entry or highlight it on the list and click Properties button to see the flow’s properties. On this window you can change the Name of the flow, add a Tag to the flow or change its Description.
Adding Task to Flow
Once you have the Flow container, scroll through the Tasks section of the pane. When you see the task which you want to add, highlight it and click Add. When you do it, the task icon will show in the flow's plan area.
To begin task configuration, please double click the aforementioned icon.
