Getting Started with Attribute Filtering
Introducing attribute filtering
Attribute filtering is a new concept which we have introduced as part of OS Select+Build. The filters can help you to narrow down the exact data you need from the OS National Geographic Database (NGD). If required, you can add attribute filters to individual feature types when you create a new bespoke recipe of OS NGD data using OS Select+Build. (The Downloading with OS Select+Build page has step-by-step instructions on how to create a new recipe.)
Attribute filtering is an optional step for those with advanced OS data knowledge.
You cannot apply attribute filters to feature types in existing recipes held in your OS Select+Build Recipe Library; they can only be added to new recipes during the recipe creation stage.
The following sub-sections give step-by-step instructions on how to add attribute filters to a new recipe and provide worked examples of creating both simple and nested filters.
How do I add attribute filters to a new recipe?
To add attribute filters to a new recipe:
Log into your OS Data Hub account.
Select Download from the main menu.
Choose OS Select+Build from the secondary navigation menu.
Click the Create a new recipe button, adding the relevant details to your recipe (see the Downloading with OS Select+Build page for more information on creating recipes).
The Advanced Filter Options panel will slide into view from the right, where you can begin to build your filter(s):
For a simple filter, select +Add rule.
For a more complex nested filter, select +Add group.
Once you have added all of your relevant filters, click Apply Filter.
Click the Create recipe button.
Worked example of creating a simple filter
In the following worked example of creating a simple filter, we will use the OS NGD Buildings Theme and select the Building Part Feature Type from the Building Features Collection. Our aim is to build a filter to select buildings where education is recorded as the land use.
To do this:
Log into your OS Data Hub account.
Select Download from the main menu.
Choose OS Select+Build from the secondary navigation menu.
Click the Create a new recipe button.
Click on the arrow to the right of Buildings within the theme selection tree to see the collections available within the theme, then click on the arrow to the right of Buildings Features to see the feature types available within that collection.
Click on the check box next to Building Part to select that feature type.
The Advanced Filter Options panel will slide into view from the right, where you can begin to build your filter(s).
We are going to build a filter where the OS Land Use Tier A attribute is set to Education.
In the Advanced Filter Options panel, click + Add rule, then select OSLandUseTierA from the first drop-down.
Leave the operator in the second drop-down as: = (i.e. the equal sign), then select Education from the third drop-down.
Click Apply filter.
Click the Create recipe button.
Your filter will return buildings where education (Education) is recorded as the land use (OS Land Use Tier A attribute).
Worked example of creating a nested filter
What if, in addition to the simple filter above (returning results for buildings with a land use of education), we want those results to show only buildings over 15 metres in height? What if you also wanted to add an additional filter to show buildings with a land use of rail? To achieve this, you could create a nested filter using the + Add group option.
To do this:
Follow the steps outlined above for creating a simple filter for Building Part until you reach the Advanced Filter Options panel step.
In the Advanced Filter Options panel, click + Add group, then select OSLandUseTierA from the first drop-down. Leave the operator in the second drop-down as: = (i.e. the equal sign), then select Education from the third drop-down.
Click + Add rule to add a second rule below the OSLandUseTierA rule.
In the second rule, select relativeHeightMaximum from the first drop-down, set the operator in the second drop-down as > (i.e. the more than sign), and type 15 in the input box.
Before continuing, select whether you would like the rules within the group to have an And or an Or condition. In this case, you should select And from the And / Or selector.
Next, click + Add group.
The application has drawn an extra box for you. Whatever rules are contained inside this box will be evaluated together, before combining with any rules outside the box.
Before continuing, select whether you would like the rule in the second group to have an And or an Or condition. In this case, you should select Or from the And / Or selector.
In the rule in the extra box, select OSLandUseTierA from the first drop-down, leave the operator as = (i.e. the equal sign) in the second drop-down, and select Transport: Rail from the third drop-down.
Click Apply filter.
Click the Create recipe button.
Your filter will return results for buildings (Building Part) that have either an education (Education) land use if that building is over 15 metres high or a railway land use (Transport:Rail).
How do I check if filters are used in an existing recipe?
To check what filters have been applied to feature types in an existing recipe:
Log into your OS Data Hub account.
Select Download from the main menu.
Choose OS Select+Build from the secondary navigation menu.
In your OS NGD Select+Build Recipe Library, scroll or search for the recipe you would like to find out more about.
Click on the name of the recipe you would like to find out more about.
You are now within the Recipe details screen, where you can view detailed information about the recipe, including the recipe's name, the date it was created, etc. If filters have been applied to the recipe, a filter icon (i.e. a black funnel symbol) will appear under the recipe name alongside text stating: 'Filters have been applied to this recipe'.
Click View all filters to view all of the filters that have been applied to feature types in the recipe.
In the example recipe below, you can see that there is a filter icon (i.e. the black funnel symbol) against the Building Part Feature Type; therefore, this feature type has filters applied to it.
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