However, this definition of accuracy immediately presents a seeming contradiction. The accuracy of an interpolation model is defined by how closely the predicted value of a location matches the actual value at that location. Perform interpolation and compare results What if some parts of the bay have low levels and other parts of the bay have high levels? Could the average be hiding some very low levels? To answer these questions, you'll create a histogram chart for the selected data. However, the line chart only showed the average dissolved oxygen level of the entire bay. These are the months when the average dissolved oxygen levels are near unhealthy levels. In the previous section, you used a line chart to determine that you should limit your analysis to the summer months of 2014. In the Tasks pane, click Finish to stop running the task.It appears that if you only use measurements within this three-month window, seasonal trends can be ignored. This is good trends can cause difficulties for interpolation workflows. The seasonal trends that you could see in the entire dataset disappear when viewing a single season. In the summer months of 2014, the average dissolved oxygen level fluctuates up and down without any clear pattern. The chart updates to only show the selected points. The task for this selection query is included in your project.
A task is a set of preconfigured steps that guide you through a workflow. You'll use a task to select measurements taken between June 15, 2014, and September 15, 2014, and sampled at a depth greater than 5 meters. While the general trend of the data rises and falls, there is a lot of variation between each observation. It is, however, encouraging to see that at no time was the average dissolved oxygen level close to 0.2 mg/L, which indicates the inability to sustain marine life.įilter the line chart to show summer 2014 dataĪlthough you've observed a seasonal cycle in the dissolved oxygen levels, you want to look more closely at individual seasons. Since anything below 5.0 mg/L is considered unhealthy, the dissolved oxygen level between June and September needs to be investigated. The average dissolved oxygen level is highest during the winter (with average levels as high as 12–13 mg/L) and lowest during the summer (with average levels as low as 5–6 mg/L). There is a clear seasonal cycle to dissolved oxygen in Chesapeake Bay. The line color of your chart may also differ, but the results are the same. Your chart content may appear different than the example image due to monitor resolution and chart size that affect which sample dates and measure values are displayed on the horizontal and vertical axis.
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