The Merging function allows you to join polygons, previously split polygons and any other objects on the map into the one. Polygons that have a common boundary will merge into one. For non-joined polygons and other object types then by joining them, they will take on the same properties as each other. To merge objects:
•Click on the first object.
•Then press and hold down the Ctrl (Control) key and select the additional objects. They should all be highlighted with their borders in red.
•Click the Merge Selected Objects button on the Toolbar 
All merged objects will inherit the properties of the first object selected. In the case of polygons, the Area field in Object Data will be for all polygons now merged.
