What type of diagram uses arrows to show an investigator's interpretation of flame or heat spread?

The correct answer is based on the function and characteristics of a vector diagram in the context of fire investigation. A vector diagram is specifically designed to illustrate direction and magnitude, using arrows to indicate the spread of flames or heat during a fire incident. This helps investigators analyze the patterns of fire spread and the factors influencing it, such as fuel availability and environmental conditions.

In fire investigations, having a visual representation of how fire spread can be crucial for understanding the dynamics of the incident. The arrows in a vector diagram point towards the direction of flame and heat movement, providing insight into the fire's behavior and aiding in the determination of its origin.

Other types of diagrams, while useful in their respective contexts, do not serve this specific purpose as effectively. Flowcharts are typically used to represent processes or decision points, while maps may show geographical features without detailing the dynamics of flame spread. Schematic diagrams can represent systems or structures but do not inherently convey the directional flow of heat or flames the way a vector diagram does.