D-15 
CHESAPEAKE BAY PROGRAM INTERPOLATOR 
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Figure D-16. Math screen with files 
chosen to "Change Over Time". The 
bdo-9707-9709.fls file contains file 
names of dissolved oxygen .EST files. 
The corresponding Julian dates for 
these .EST files are read from the do.jul 
file. In this example, a new .EST file - 
Change.est - is created which contains 
the linear trend for each cell over the 
time interval of the bdo-9707-9709.fls 
file. The Change.est cell values are per¬ 
centage change over time, categorized 
by the selection criteria identified in 
the pc.rng file. In this example, "Ignore 
missing values" has not been selected. 
CHESAPEAKE BAY 
Water Quality Analysis 
Total Phosphorus Percent Change J«1 2.1984-Dec 18, 199? 
PL AN VIEW 
Susquehanna 
Legend 
□ >-103: 
■■ -5*~-10X 
C=) 0*~-5* 
CD 03:~5X 
C3 5*~103: 
E3 >10X 
Not Calculated 
Atlantrc 
Patuxent “S 
Potomac 
, r- 
Jarnes 
^ Rappahannock 
I 
DEPTH PROFILE 
Figure D-17. Plot of total phosphorus as a "Change Over Time". In this 
example, a new .EST file - tp8497.est - was created which contains the linear 
trend for each cell over the time interval (July 1984 through December 1997) 
of the tp8497.fIs file. The tp8497.est cell values are percentage change over 
time, categorized by the selection criteria identified in the pc.rng file. The 
percentage change categories for total phosphorus mass (kg) are: >10% 
increase (red); 5 to 10% increase (pink); 0 to 5% increase (yellow); 0 to 5% 
decrease (light blue); 5 to 10% decrease (dark blue); and greater than 10% 
decrease (green). In this example, "Ignore missing values" was selected so 
that a trend on any available data was calculated. 
appendix d • User Guide and Documentation for the Chesapeake Bay Interpolator 
