What does a node represent in a GIS structure?

In the context of GIS, a node is defined as a point that typically represents a vertex at the beginning or end of an edge in a vector data structure. This is particularly significant in network analysis, where nodes can signify intersections, endpoints, or other critical points in a spatial dataset.

Nodes serve as essential elements in the representation of spatial relationships in features such as transportation networks, utility lines, or any set of connected paths. By delineating the start and end points of edges, nodes enable GIS software to analyze connections, flows, and accessibility within a geographic space, allowing for various operations like shortest path analysis and connectivity assessment.

In contrast, the other options refer to elements that do not accurately reflect the definition of a node in the structural context of GIS. For example, a standalone point lacks the relational context tied to edges. A connecting line describes edges themselves rather than the points at their vertices. Raster data represents a different type of data model focused on grid cells and continuous data rather than discrete points or connections. Thus, the definition directly aligns with the role of nodes in the GIS framework as pivotal junctions that facilitate spatial analysis through their relationship with edges.