D-22 
Figure D-28 illustrates a time series plot of the mass of total phosphorus computed 
by the procedure described in. The mass of total phosphorus was computed for 
Chesapeake Bay and tidal tributary rivers using monthly mean data for each station 
at each depth for the period of record. The “Date” and “Total” (sum of all columns 
in mass tile) columns were used from the mass file (.mas) to make this plot. The 
linear trend line is superimposed to show the general rate of decline. This plot was 
created by opening the tp8497.mas file in Excel, selecting the line chart button, 
selecting the “Start_Date” and “Total” columns, and adjusting the legends and titles 
as necessary to create the time series plot. The linear trend was added by selecting 
the time series followed by “Chart:Add Linear Trendline”. 
Mass of Total Phosphorus in Chesapeake Bay and 
Tidal Tributaries Computed by Interpolation 
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Figure D-28. TTime series plot of the mass of total phosphorus. 
FILE DEFINITIONS AND STRUCTURE 
INPUT DATA FILE (.d3d) 
Monitoring data are required for the Interpolator to compute values. The file should 
contain one value per depth per station for which data exist. If replicate values were 
measured at some or all stations, they should be averaged at each station depth so 
that only one value exists per depth per station. The overall data can represent one 
cruise, a season of cruises, or a decade of data—there are no limitations on what the 
data represent—that is up to the user to determine. It is best, statistically, to provide 
as many data as possible. One method is to linearly interpolate values from surface 
to bottom before creating the data file for the Interpolator. This will provide more 
data for the Interpolator if it is valid to do so for the desired data. For the 2D inter¬ 
appendix d 
User Guide and Documentation for the Chesapeake Bay Interpolator 
