Trend Graphing Instructions

1. Plots are selected from the 'Stations' dropdown list and the 'Items' (pollutants or meteorological parameters) drop down list. (NOTE: Not all items are available at every station, and in fact stations are sited differently depending on the pollutant.) To plot a station or item just select a different choice from the list, or click on the buttons to the right of the name ('>' plots the specific station or item; '>>' selects all of the stations or items in the list). To remove a plot, select the name in the list to be removed and click the '<' button or click the 'Clear' button to remove all plots.
2. The default duration 'Time interval' of the plot is set at '1 Week' (7 days). The time interval is selectable from 1 day up to 1 year.
3. The default end and start dates for the default 1 week plot is today’s date minus 6 days. The start date is selectable from January 1, 1990 through the current date. Change the start date by selecting a different month, day, or year from the dropdown lists. You can also change the start day 1 day at a time by clicking on the 'Change Start 1 Day' buttons. (NOTE: The stations and items in the dropdown lists are listed only if data is available for any period within the start and end dates.)
4. Multiple plots are possible according to the following selections:
   • "1 Station & Multiple Items" – the station dropdown list is populated with all stations that were operating within the start and end dates; the item dropdown list is filled with only items that were sampled at the selected station.
   • "1 Item & Multiple Stations" – the item dropdown list is populated with all items that were sampled within the start and end dates; the station dropdown list is filled with only stations where the item was sampled.
   • "Stations with Same Multiple Items" – the item dropdown list is populated with all items that were sampled within the start and end dates; multiple items can be selected one at a time from the dropdown list; the station dropdown list contains only stations that sampled for all of the selected items.
5. Three different averaging periods are available for displaying all items — 1-hour, 8-hour, and 24-hour averages. An additional selection "AQI" is also available to plot items used in calculating the Air Quality Index (AQI) and are displayed in AQI units.
• If "Select Averaging For Each" is selected, the averages are individually selectable for any displayed plot up to a maximum of six (6); after 6 plots they default to 1-hour displays. It is useful at times to display 2 or more plots of the same item with different averaging to see the smoothing result of longer averaging periods, especially where the standards are written for 8-hour or 24-hour averages.
• If "Select Averaging For All" is selected, all plots are forced to the selected average.
6. The list boxes titled Interval Average, Interval Maximum, and Interval Minimum shows the average, maximum, and minimum values for each plot of the selected time interval. For an average to be displayed, 75% of the expected values for the time interval are required.
7. The 'Display Air Quality (AQI) Categories' options are enabled if an item is used for the Air Quality Index. If a category is selected, the background of the plots will display the AQI categories for the selected item. (Note: If "AQI" is selected as an averaging period and you choose to display AQI categories the selection will be forced to "AQI units".
8. The 'Display Markers' options are enabled if a Time Interval of '1 Day' or "3 Days" is selected. Choosing "Yes" will display a triangle marker for each value of the plot.
9. The default y-axis scaling is auto-scaling. To manually change the scaling, click the "Up" or "Dn" button.
10. If you wish to change the position or hide the legend on the chart select one of the options.