The terrain grid file contains 1 header record, followed by any number of data records.  The file is read as a free-format ASCII file.  The header record contains the following information:


     nx, ny, xllm, yllm, xurm, yurm, sizem


     nx, nynumber of data points in x (Easting) and y (Northing) directions;


     xllm, yllmUTM coordinates (in meters) of the point at the lower left corner of the grid;


     xurm, yurmUTM coordinates (in meters) of the point at the upper right corner of the grid; and


     sizemspacing between grid points in both the x and y directions, in meters.



The data records are ordered by rows.  The first row contains nx terrain elevations ordered from west to east, starting at point (XLLM, YLLM).  Row 2 contains the data for the next row to the north in the grid.  There are a total of ny rows of data in the terrain grid file.  The default units for terrain elevations in the terrain grid file are meters MSL.  However, the user may specify terrain elevations to be in units of feet by adding the optional TG ELEVUNIT FEET card.  The order of the ELEVUNIT card on the TG pathway is not important.  The maximum number of points in the terrain grid file is controlled by the MXTX and MXTY parameters in the DEPVAR.INC file. 




     The ISCEV (EVENT) model is specifically designed to facilitate analysis of source contributions to specific events for short term averages (less than or equal to 24 hours).  These events may be design concentrations generated by the ISCST model, occurrences of violations of an air quality standard, or user‑specified events.  These events are input to  the ISCEV model through the EVent pathway.  Each event is defined by an averaging period and specific data period, a source group, and a receptor location.  Since the locations are only of interest in combination with particular averaging and data periods, the REceptor pathway is not used by the EVENT model.


     There are two keywords that are used to define the events on the EV pathway.  The EVENTPER keyword defines the averaging period, data period and source group, while the EVENTLOC keyword defines the receptor location for the event.  Each event is also given an alphanumeric name that links the two input cards for that event.


     The syntax and type of the EVENTPER and EVENTLOC keywords are summarized below:



EV EVENTPER  Evname  Aveper  Grpid  Date


EV EVENTLOC  Evname   XR= Xr    YR= Yr  (Zelev)  (Zflag)

         or  Evname  RNG= Rng  DIR= Dir (Zelev)  (Zflag)


Mandatory, Repeatable


where the parameters are as follows:


Evname ‑     event name (an alphanumeric string of up to 8 characters),


Aveper ‑     averaging period for the event (e.g. 1, 3, 8, 24 hr)


Grpid  ‑     source group ID for the event (must be defined on SO pathway),


Date   ‑     date for the event, input as an eight digit integer for the ending hour of the data period (YYMMDDHH), e.g. 84030324 defines a data period ending at hour 24 on March 3, 1984.  The length of the period corresponds to Aveper.


XR=    ‑     X‑coordinate (m) for the event location, referenced to a Cartesian coordinate system


YR=    ‑     Y‑coordinate (m) for the event location, referenced to a Cartesian coordinate system


RNG=   ‑     distance range (m) for the event location, referenced to a polar coordinate system with an origin of (0., 0.)


DIR=   ‑     radial direction (deg.) for the event location, referenced to a polar coordinate system with an origin of (0., 0.)


Zelev  ‑     optional terrain elevation for the event location (m)


Zflag  ‑     optional receptor height above ground (flagpole receptor) for the event location (m)



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