What does the vertical axis mean in the “surface points in time” visualization?
In the “surface points in time” visualization, the vertical axis represents the distribution in time, not the actual three-dimensional physical location or depth. Each point still has an x, y horizontal location, but the plotted vertical extent encodes elapsed time, as illustrated by lengths corresponding to 250 days and around 500 days.
Conditions
- The visualization is the left panel labeled “surface points in time”.
- The data represents groundwater measurements over time.
Reasoning, step by step
- Identify the left visualization labeled “surface points in time”.
- Note that each point has an x, y horizontal location.
- Observe that the vertical extent of the stems represents time rather than physical depth.
- Read the temporal scale, such as the marked length of 250 days, to interpret the time distribution.
Example
The lecturer explicitly states that in the time-distribution view, the z value does not represent the actual three-dimensional location but rather distribution in time, pointing to a marked length labeled “250 days”.
Common misconceptions
- Assuming that the upward axis always means spatial depth because both spatial and temporal visualizations use a vertical direction.
- Confusing the temporal scatter of the wells with their vertical spatial scatter.
Watch the explanation
Explore next
- Why does the groundwater example require quadrivariate interpolation instead of ordinary 2D or 3D interpolation?
- What is the difference between interpolation and approximation in the bivariate formulation?
- How do you calculate the expected value from an explicit outcome table with mutually exclusive outcomes?
Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.