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In very simple terms, Subtypes are used to classify or group attributes of common value or range in a feature layer. Such attributes usually share a common alphanumeric or numeric, code or range value. Subtypes and Attribute domains work together to also define certain limits and restrictions for similar types of attribute values.
In the demonstration, the Mast_ID for each Mast_operator is created as a subtype of the feature layer – Telecom masts. The Subtypes are inputted into the numerical field – Mast_ID and represent coded values for each Mast operator.
– Subtypes can only be created in fields of Feature Classes not Shape files.
– A Project Geodatabase will have to be created to have feature classes.
Creating Subtypes in the field -Mast_ID. This field will designate codes for each Telecom mast operator.
Create a geodatabase file. Right Click on the geodatabase > New > Feature Class. The demo feature class is named Telemasts. The feature class should appear under the geodatabase.
Right Click on the Telemast feature class > Properties
In the Feature Class Properties window, Go to Fields tab, type in a new field and use the drop down list to indicate its Data type. Fields used to create Subtypes are always numeric in data type. for the demo, our field is Mast_ID and it’s a short integer. Click Apply.
Go to the Subtypes tab. For Subtype Field- click the drop down list and choose the integer field, for demo- Mast_ID. On the default subtype, the first code is usually taken as default. In the Subtypes Table, fill in the codes and their description. Make the description short as that is what will show on the attribute table drop down list.
Start editing on the image and then Right Click on the Telemast feature layer > Open Attribute layer. In the Mast_ID field, a drop down list makes available all the descriptions of the subtypes.
As illustrated in the demo, Point 3 shows the drop down list and all the mast_operators represented as Subtypes.
Using the Symbol levels on the feature layer, the demo illustrates the three subtypes representing different Mast_Operators.