In geospatial modeling, what does a 2.5D model refer to?

In geospatial modeling, a 2.5D model specifically refers to a terrain model where each x/y coordinate is associated with a single z-value. This means that while the model represents a surface in three-dimensional space, it does not allow for vertical complexity at each point; rather, it maintains a single elevation value for each horizontal location. This approach effectively simplifies the representation of terrain, such as in digital elevation models, where the focus is on the height above a reference plane (like sea level) without accommodating features like overhanging cliffs or multi-level structures.

The other options suggest different interpretations of 2.5D. One mentions multiple z-values, which would imply a more complex, true 3D model, while another describes a purely two-dimensional representation that does not capture elevation at all. The mention of vertical features only addresses a specific type of data representation and does not align with the standard definition of a 2.5D model, which is fundamentally concerned with a unidimensional elevation format integrated into a 2D spatial framework.