Reading photographs as evidence

Overview

Photograph genuinely good for in a decision-making exercise and blind spots of a photograph as evidence.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a photograph genuinely good for in a decision-making exercise?

   Model answer

   Showing physical and visual conditions that are hard to quantify: the state of buildings, the condition of a coastline or channel, the character and quality of a landscape, existing land use, vegetation, congestion, and the scale of one feature against another. It is the resource that supports arguments about amenity, dereliction and visual impact, which statistics handle badly.

2. 2

   What are the blind spots of a photograph as evidence?

   Model answer

   It is one viewpoint at one moment, chosen and framed by somebody. It cannot show frequency, trend or magnitude, it carries no scale unless something of known size is in shot, and season, weather and time of day change the impression considerably. It may also be dated, so what it shows may no longer exist, and it was selected for the booklet by someone with a purpose.

3. 3

   Distinguish between what an oblique aerial photograph and a vertical aerial photograph each give you.

   Model answer

   A vertical photograph is taken looking straight down and behaves much like a map: it shows the layout, extent and pattern of land use with consistent scale across the image, and is best for measuring area and relationships. An oblique is taken at an angle and shows height, building facades, relief and the view a person on the ground would recognise, making it better for judging visual impact but unreliable for anything measured.

4. 4

   How do you turn the observation that a photograph shows a derelict site into usable evidence?

   Model answer

   Say what specifically indicates dereliction - broken windows, hoarded frontages, vegetation growing through hard standing, no vehicles or activity - then attach it to the decision: the site is visibly out of productive use, so redevelopment carries a lower opportunity cost than building on the greenfield alternative, and the existing visual impact is already poor. The inference has to be stated; the reader will not make it for you.

5. 5

   What can you reasonably infer from a photograph, and where should you stop?

   Model answer

   You can reasonably infer physical condition, land use, approximate relative size and obvious constraints such as steep slopes or a narrow street. You should stop short of inferring how often something happens, how many people are involved, how much anything costs, or what local opinion is. Those need a different resource, and claiming them from a photograph is the commonest overreach in this exercise.

6. 6

   A photograph shows a flooded street. Why is that weaker evidence for flood risk than it looks?

   Model answer

   Because a single image proves the street flooded once, on one occasion, to a depth you cannot measure precisely. Risk is about frequency and magnitude, which requires a record of past events, discharge data or a flood-risk map. The photograph is still valuable - it establishes that flooding reaches property and shows the depth relative to doors and vehicles - but the case for or against a defence needs the numbers alongside it.

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