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IAS METHOD FOR 2D DATA ANALYSIS ON PC's
Andrew G. Detwiler and Kenneth R. Hartman
Institute of Atmospheric Sciences
South Dakota School of Mines and Technology
501 E. St. Joseph Street
Rapid City, SD 57701-3995
CHAPTER 4: TOUCH2D PROGRAM
This program allows the investigator to visually scan and, if desired,
modify some of the parameters associated with individual particles. (Currently,
a particle's habit, diameter, and mass may be altered.) TOUCH2D is usually
run to doublecheck the accuracy of the automated habit classification program
and to provide the user with a way of editing those particles that the
eyeball interprets differently than does the computer algorithm. The program
is called in a fashion similar to PRELIM2D; namely, by making sure the
program file is in the current directory or directory path and entering
TOUCH2D
The user is then prompted for the name of the input archive file and given
the option of creating a modified output file. If one merely wishes to
view the particles on the graphics screen, then an output file should not
be selected.
Some information relating to the input file is displayed (Fig. B1),
and then a menu like the one in Figure B2 appears. A brief description
of some of the less obvious items in the SETUP menu follows:
Setup Menu
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Plt Size - This is the magnification factor (more or less) of the
particle images when they are drawn on the screen. A value of 0 means that
one probe diode will be represented by one screen pixel. A value of 1 results
in each diode being represented by a rectangular block of pixels (4 x 3
for EGA monitors) that yields an approximate 1:1 X to Y appearance. The
choices of 2, 3, or 4 are merely the same thing as 1, but with a corresponding
magnification factor.
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Part Lab - Short for particle label, these two columns list various
parameters which may be output on the screen above the graphical representation
of the particle images. Only the highlighted items will be displayed when
the particles are drawn.
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Habit - Classification of particle based on geometrical appearance.
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Time Lapse - time in microseconds between the arrival of the current
particle and its predecessor.
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Area Ratio - one of several measures of roundness. The actual particle
cross-sectional area is compared to that of a circle with the same "diameter"
as that attributed to the particle. The value is expressed as a percentage.
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Heyms Diam - The Heymsfield diameter is normally taken to be the
greater of the maximum X or Y span of the particle, although sometimes
the diameter may be greater if the particle has been reconstructed. This
occurs for those particles which were only partially in view. In this case,
the numeric value displayed on the screen is followed by a plus sign.
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Holyroyd Diam - It is the longest distance through the particle,
not being restricted to purely horizontal or vertical distance (e.g., a
diagonal).
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Mass (Andy) - particle mass as computed by Andy Detwiler's best
guess empirical algorithm. Units are in nanograms.
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Mass (Sphere) - particle mass assuming a spherical particle with
a diameter equal to the Heymsfield diameter. This is perhaps more accurate
than Andy's method for liquid particles, but less accurate for solid particles.
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PDA Ratio - perimeter x diameter/area. This yields a measure of
roundness and regularity of shape. A snowflake, for instance, would have
a greater value than a water drop.
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Equiv Circle - equivalent diameter of a spherical particle having
a cross-sectional area equal to that of the particle in question.
When all the desired items have been selected (highlighted), press the
"R" key and confirm that you're ready to proceed. The program scans through
the archive file until it finds the first record within the specified time
range. It clears the screen and outputs buffer information on the left-hand
side and an Action menu on the right (Fig. B3). Unlike PRELIM2D, the user
must interactively move from one buffer to another in the Action menu.
When all buffers within the selected time range have been viewed or modified,
the screen returns to the Setup menu. However, the user may return to the
Setup menu at any time to modify menu selections (such as specifying a
different set of labels). When the end of file is reached, or the user
selects "E" for exit, the program copies all remaining records to the output
file, if one was selected, and then terminates. Pressing CTRL-C from any
screen will immediately terminate the program also, but if there is an
output file, all remaining records on the input file will not get copied.
This is referred to as not exiting gracefully.
Action Menu
The functions that the action menu may perform are as follows:
SETUP menu
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Return to previous screen display, usually
to change the particle labels that have been chosen or to select a different
time range. |
| Next Record |
Read next record and display habit and buffer info. |
| Plot Habit |
Draw the graphical representation of particles within a particular
habit or all habits. When this option is selected, the action menu is replaced
on the right-hand side by the select habit menu. |
| Continue Plot |
This selection is only visible if more particles of the selected habit
remain to be displayed; i.e., not all of them fit on the screen at one
time. |
| Previous Record |
Rereads the previous record and displays habit breakdown. This option
cannot be selected consecutively without an intervening Next Record command
or a new time range via the Setup menu. In other words, if one is proceeding
through an archive file and displaying buffer number n, it is possible
to move back to record n-1, but not possible to then immediately request
buffer n-2. |
| Diameter Range |
Allows the user to set a minimum and maximum diameter range so that
only particles with diameters within that range will be plotted on the
screen. The program displays the current settings and prompts the user
for new values. |
| Record Summary |
Redisplay the statistical information for the current buffer on the
left-hand screen (which presumably was erased when particles were plotted). |
| Change Particle |
Modify either a particle's habit designation, Heymsfield diameter,
or calculated mass. Sometimes modifying one of these will, in turn, affect
other calculated values. When this option is selected, further menus will
appear to guide the user through the change process. (Note: This option,
like the Continue Plot one, is not visible until some particle(s) have
been displayed on the screen.) |
| View Buffer |
This option is not available on CGA monitors. When selected, it enables
the screen display to be toggled between the current display and one similar
to the VIEWIMG program; namely, one which displays the entire 2D buffer,
as in Figure B9. |
With the exception of the Setup menu, which occupies the entire screen,
all other menus appear on the right portion of the screen, with either
text or graphics output on the left side. In addition to the two main menus,
there are several other screen menus which appear, depending upon prior
choices. They are hopefully self-explanatory once they appear, but perhaps
a brief discussion of them here might be beneficial.
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Select Habit Menu - The different habits which may be selected are
displayed. The user positions the cursor at the desired habit (or All Habits)
and activates that choice with the Enter key or mouse. This menu appears
when the user selects the Plot Habit option or when he wishes to modify
a particle's habit. (See Fig. B4). Images of the selected particles, along
with their chosen attributes, are displayed on the left screen as in Figure
B6.
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Diameter Range Menu - This is not really a menu, but rather two
successive prompts to obtain new minimum and maximum diameter values. Being
within the acceptable range is one of the criteria which must be met before
a particle is displayed on the screen. The initial values are 0 and 50000
(essentially everything). (Fig. B5).
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Select Particle Menu - This menu appears when the Change Particle
entry of the Action Menu is chosen. One chooses from the particle numbers
displayed on the left screen, as in Figure B7.
Modify Particle Menu - The particle's current values for
habit type, Heymsfield diameter, and mass calculation are displayed, in
that order. The user may click on any of these fields and then enter new
guesses. Note that a change in one of the first two fields may result in
a recomputation of the mass values, so if a specific mass number is desired,
it should be entered after any other changes. To make the changes permanent,
press the Save Changes entry. If you have second thoughts, press Esc or
the middle mouse key. An example appears in Figure B8.
Introduction
Chapter 1 - Discussion of Probes
Chapter 2 - Particle Shadow Classification
Chapter 3 - PRELIM2D Program
Chapter 5 - ANALYZE and ANELAP
References
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