D-10 
INTERPOLATE BUTTON 
Click the Interpolate Button to select the Interpolate screen (Figure D-l 1). Select 
the interpolator settings that match your requirements. The 3D Inverse-Distance 
Squared model is the 3-dimensional interpolator model. The 2D Inverse-Distance 
Squared model uses the same code as the 3D interpolator model except that only one 
layer of cells are computed—cells for each depth below the surface cell are set to 
missing (normally -9). The 2D Octant Search model computes values for cells in 
only one layer, however, the data used for computing each cell value are selected 
from data in each surrounding octant. For instance, for a given cell, the data used for 
calculation would include 4 data points from each surrounding octant, or a total of 
32 data points. The model will use fewer than the total data in each octant if insuffi¬ 
cient data exist. The model uses as many data as are available for each octant, up to 
the maximum requested number of data points. The octant search model is used to 
reduce the bias from sampling schemes that collect continuous strings of data, such 
as aircraft monitoring that collect many data points in well defined flight tracks. The 
run-time for the octant search model is significantly longer due to the extensive 
sorting required to select data from each data octant. 
The “Trace Level” selects the amount of detail written to the “.LOG” file. A “Trace 
Level” of “2” provides general interpolator statistics. A “Trace Level” of “3” 
provides information about the data values used in the computations for each region. 
A “Trace Level” of “4” provides information about individual cell computations. A 
“Trace Level” of “5”, “6”, or “7” provides increasing information about data values, 
distances, and octants. Increasing the “Trace Level” value is useful for investigating 
the performance of the interpolator. 
The “Convert .EST to .TXT” button will create a .txt file that can be imported into 
Arc/Info or Arc View. The .txt files are a full matrix of values, 57 columns wide, with 
all missing or non-existent cell values designated as missing values (normally -9), 
comma delimited, and column headings and text strings are enclosed in quotes. Each 
row in the .txt file represents numbers from 1 column of water from top to bottom, 
1 cell wide by n cells deep. Additional columns are appended to the .txt file for 
bottom, minimum, maximum, mean, and sum values. 
The “Convert .EST to .T3D” button will create a .txt file that can be imported other 
applications. The .t3d files are 4 columns wide, comma delimited, contain the x 
value, y value, negative z value, and the estimated value. There are no column head¬ 
ings. Missing values are included and are coded based on what was selected during 
the interpolation. 
The interpolator mode can be set to “Interactive” or “Batch”. In interactive mode, the 
chosen file is interpolated as defined in Figure D-l 1. In “Batch” mode, a job file is 
selected which provides the information needed to interpolate a series of files under 
machine control (Figure D-l2). The “.job” file can be built interactively by pressing 
the “Save to Batch Job” button after selecting the run parameters for each desired file 
(Figure D-l3). The “Batch Job” can be executed by pushing the “Run Batch Job” 
button. 
appendix d 
User Guide and Documentation for the Chesapeake Bay Interpolator 
