What GIS operation combines all input features while preserving all areas?

The operation that combines all input features while preserving all areas is the union operation. In geographic information systems (GIS), union combines multiple layers of spatial data, ensuring that the resulting output retains all the areas from the input features. This means that if two or more polygons overlap, the union will create a new polygon that encompasses both, maintaining all parts of each original feature.

The union operation is particularly useful in scenarios where you want to analyze the total area covered by multiple datasets and understand the overall spatial distribution of features. It provides a comprehensive view by merging all features, rather than only showing the areas where they intersect.

In contrast, the intersection operation focuses on the overlapping areas between features and does not maintain non-overlapping areas. Buffering creates zones around features but does not combine features in a way that preserves their original areas. The clip operation extracts features from one layer based on the geometry of another but does not combine them, instead limiting output to areas that overlap. This highlights the importance of understanding the specific functions of each operation in GIS to utilize them effectively for spatial analysis.