SPLAT!(1)                 KD2BD Software                SPLAT!(1)



NAME
       splat  -  A Signal Propagation, Loss, And Terrain analysis
       tool

SYNOPSIS
       splat [-t transmitter_site.qth] [-r receiver_site.qth] [-c
       rx_antenna_height_for_los_coverage_analysis         (feet)
       (float)]   [-L   rx_antenna_height_for_Longley-Rice_cover-
       age_analysis  (feet) (float)] [-p terrain_profile.ext] [-e
       elevation_profile.ext] [-h height_profile.ext]  [-l  Long-
       ley-Rice_profile.ext]   [-o  topographic_map_filename.ppm]
       [-b        cartographic_boundary_filename.dat]         [-s
       site/city_database.dat]    [-d   sdf_directory_path]   [-m
       earth_radius_multiplier   (float)]   [-R    maximum_cover-
       age_range (for -c or -L) (miles) (float)] [-n] [-N]

DESCRIPTION
       SPLAT!  is  a  simple,  yet powerful terrain analysis tool
       written for Unix and Linux-based workstations.  SPLAT!  is
       free software.  Redistribution and/or modification is per-
       mitted under the terms of the GNU General  Public  License
       as  published by the Free Software Foundation, either ver-
       sion 2 of the License or any later version.   Adoption  of
       SPLAT!  source code in proprietary or closed-source appli-
       cations is a violation of this license,  and  is  strictly
       forbidden.

       SPLAT!  is distributed in the hope that it will be useful,
       but WITHOUT ANY WARRANTY, without even  the  implied  war-
       ranty  of MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR-
       POSE. See the GNU General Public License for more details.

INTRODUCTION
       SPLAT!  is  a terrestrial RF propagation analysis tool for
       the spectrum between 20  MHz  and  20  GHz,  and  provides
       information  of interest to communication system designers
       and site engineers.  SPLAT! determines great  circle  dis-
       tances  and  bearings  between  sites,  antenna  elevation
       angles (uptilt),  depression  angles  (downtilt),  antenna
       height  above mean sea level, antenna height above average
       terrain, bearings and  distances  to  known  obstructions,
       Longley-Rice   path   loss,  and  minimum  antenna  height
       requirements needed to establish line-of-sight  communica-
       tion  paths absent of obstructions due to terrain.  SPLAT!
       produces reports, graphs, and highly  detailed  and  care-
       fully  annotated  topographic maps depicting line-of-sight
       paths, path loss, and expected coverage areas of transmit-
       ters  and repeater systems.  When performing line-of-sight
       analysis  in  situations  where  multiple  transmitter  or
       repeater  sites are employed, SPLAT! determines individual
       and mutual areas of coverage within the network specified.

       SPLAT!  operates  in  two  modes: point-to-point mode, and
       area prediction mode.  These modes may  be  invoked  using
       either  line-of-sight  (LOS)  or  Irregular  Terrain (ITM)
       propagation models.  True Earth, four-thirds Earth, or any
       other  Earth radius may be specified by the user when per-
       forming line-of-sight analysis.

INPUT FILES
       SPLAT! is a command-line  driven  application,  and  reads
       input  data  through a number of data files.  Each has its
       own format.  Some files are mandatory for successful  exe-
       cution  of the program, while others are optional.  Manda-
       tory files include SPLAT  Data  Files  (SDF  files),  site
       location files (QTH files), and Longley-Rice model parame-
       ter files (LRP files).  Optional files  include  city/site
       location files, and cartographic boundary files.

SPLAT DATA FILES
       SPLAT!  imports topographic data in the form of SPLAT Data
       Files (SDFs) that may be generated from a number of infor-
       mation  sources.   In  the United States, SPLAT Data Files
       are most often derived from U.S.  Geological Survey  Digi-
       tal  Elevation  Models  (DEMs)  using the usgs2sdf utility
       included with SPLAT!.  USGS Digital Elevation Models  com-
       patible with this utility are available at no cost via the
       Internet                  at:                  http://edc-
       sgs9.cr.usgs.gov/glis/hyper/guide/1_dgr_dem-
       fig/index1m.html.

       SPLAT Data Files contain  topographic  elevations  to  the
       nearest  meter  above  mean  sea  level  for  1-degree  by
       1-degree regions of the earth with a resolution  of  3-arc
       seconds.   SDF files can be read in either standard format
       (.sdf) as generated by the usgs2sdf utility, or  in  bzip2
       compressed  format  (.sdf.bz2).   Since uncompressed files
       can be slightly faster  to  load  than  compressed  files,
       SPLAT!  searches  for  the needed SDF data in uncompressed
       format first.  If such data cannot  located,  then  SPLAT!
       tries  to read the data in bzip2 compressed format.  If no
       compressed  SDF  files  can  be  found  for   the   region
       requested, SPLAT! assumes the region is over water or out-
       side the United States, and will assign  an  elevation  of
       sea-level to these areas.  This feature of SPLAT! makes it
       possible to perform path analysis not only over land,  but
       also between coastal areas not represented by USGS Digital
       Elevation Model Data since they are  devoid  of  any  land
       masses.   However, this behavior of SPLAT! underscores the
       importance of having all the SDF files  required  for  the
       region  being  analyzed  if  meaningful  results are to be
       expected.

SITE LOCATION (QTH) FILES
       SPLAT! imports site location  information  of  transmitter
       and  receiver  sites  analyzed  by  the program from ASCII
       files having a .qth  extension.   QTH  files  contain  the
       site's  name,  the site's latitude (in degrees North), the
       site's longitude (in degrees West), and the site's antenna
       height above ground level (AGL).  A single line-feed char-
       acter separates each field.  The antenna height is assumed
       to be specified in feet unless followed by the letter m or
       the word meters in either upper or lower  case.   Latitude
       and longitude information may be expressed in either deci-
       mal format (74.6889) or degree, minute, second (DMS)  for-
       mat (74 41 20.0).

       For  example,  a  site location file describing television
       station WNJT, Trenton, NJ (wnjt.qth) might  read  as  fol-
       lows:

               WNJT
               40.2833
               74.6889
               990.00

       Each transmitter and receiver site analyzed by SPLAT! must
       be represented by its own site location (QTH) file.

LONGLEY-RICE PARAMETER (LRP) FILES
       SPLAT! imports  Longley-Rice  model  parameter  data  from
       files  having  the  same base name as the transmitter site
       QTH file, but carrying a .lrp  extension,  thus  providing
       simple  and  accurate correlation between these associated
       data sets.  The format for the Longley-Rice model  parame-
       ter files is as follows (wnjt.lrp):

               15.000  ; Earth Dielectric Constant (Relative per-
       mittivity)
               0.005   ; Earth Conductivity (Siemens per meter)
               301.000 ; Atmospheric Bending Constant (N-units)
               700.000 ; Frequency in MHz (20 MHz to 20 GHz)
               5       ; Radio Climate (5 =  Continental  Temper-
       ate)
               0       ; Polarization (0 = Horizontal, 1 = Verti-
       cal)
               0.5     ; Fraction of  situations  (50%  of  loca-
       tions)
               0.5     ; Fraction of time (50% of the time)

       If  an LRP file corresponding to the tx_site QTH file can-
       not be found, SPLAT! scans the current  working  directory
       for  the  file "splat.lrp".  If this file cannot be found,
       then the default parameters listed above will be  assigned
       by  SPLAT! and a corresponding "splat.lrp" file containing
       this data will be written to the  current  working  direc-
       tory.

       Typical Earth dielectric constants and conductivity values
       are as follows:

                                  Dielectric Constant  Conductiv-
       ity
               Salt water       :        80                5.000
               Good ground      :        25                0.020
               Fresh water      :        80                0.010
               Marshy land      :        12                0.007
               Farmland, forest :        15                0.005
               Average ground   :        15                0.005
               Mountain, sand   :        13                0.002
               City             :         5                0.001
               Poor ground      :         4                0.001

       Radio climate codes used by SPLAT! are as follows:

               1: Equatorial (Congo)
               2: Continental Subtropical (Sudan)
               3: Maritime Subtropical (West coast of Africa)
               4: Desert (Sahara)
               5: Continental Temperate
               6:  Maritime  Temperate,  over  land  (UK and west
       coasts of US & EU)
               7: Maritime Temperate, over sea

       The Continental Temperate climate is common to large  land
       masses  in  the temperate zone, such as the United States.
       For paths shorter than 100 km, there is little  difference
       between Continental and Maritime Temperate climates.

       The  final  two  parameters in the .lrp file correspond to
       the statistical  analysis  provided  by  the  Longley-Rice
       model.   In  this example, SPLAT!  will return the maximum
       path loss occurring 50% of the time (fraction of time)  in
       50%   of  situations  (fraction  of  situations).   Use  a
       fraction of time parameter of 0.97 for digital television,
       0.50  for analog in the United States.  Isotropic antennas
       are assumed.

       For  further  information  on   these   parameters,   see:
       http://elbert.its.bldrdoc.gov/itm.html                 and
       http://www.softwright.com/faq/engineering/prop_long-
       ley_rice.html

CITY LOCATION FILES
       The  names  and locations of cities, tower sites, or other
       points of interest may imported and be  plotted  on  topo-
       graphic  maps  generated  by  SPLAT!.   SPLAT! imports the
       names of cities and locations from ASCII files  containing
       the  location's  name,  the  location's  latitude, and the
       location's longitude.  Each field is separated by a comma.
       Each  record is separated by a single line feed character.
       As was the case with the .qth files, latitude  and  longi-
       tude  information  may  be  entered  in  either decimal or
       degree, minute, second (DMS) format.

       For example (cities.dat):

               Teaneck, 40.891973, 74.014506
               Tenafly, 40.919212, 73.955892
               Teterboro, 40.859511, 74.058908
               Tinton Falls, 40.279966, 74.093924
               Toms River, 39.977777, 74.183580
               Totowa, 40.906160, 74.223310
               Trenton, 40.219922, 74.754665

       A total of five separate city data files may  be  imported
       at  a time.  There is no limit to the size of these files.
       SPLAT! reads city data sequentially, and plots only  those
       locations  whose positions do not conflict with previously
       plotted locations when generating topographic maps.

       City data files may be generated manually using  any  text
       editor,  imported from other sources, or derived from data
       available from the U.S. Census Bureau  using  the  cityde-
       coder  utility  included with SPLAT!.  Such data is avail-
       able free of charge via the Internet  at:  http://www.cen-
       sus.gov/geo/www/cob/bdy_files.html,  and  must be in ASCII
       format.

CARTOGRAPHIC BOUNDARY DATA FILES
       Cartographic boundary data may also be  imported  to  plot
       the  boundaries  of  cities,  counties, or states on topo-
       graphic maps generated by SPLAT!.  Such data  must  be  of
       the  form  of  ARC/INFO Ungenerate (ASCII Format) Metadata
       Cartographic Boundary Files, and are  available  from  the
       U.S.   Census  Bureau via the Internet at: http://www.cen-
       sus.gov/geo/www/cob/co2000.html#ascii and  http://www.cen-
       sus.gov/geo/www/cob/pl2000.html#ascii.   A  total  of five
       separate cartographic boundary files may be imported at  a
       time.   It  is not necessary to import state boundaries if
       county boundaries have already been imported.

PROGRAM OPERATION
       SPLAT! is invoked via the command-line using a  series  of
       switches  and arguments.  Since SPLAT! is a CPU and memory
       intensive application, this type  of  interface  minimizes
       overhead,  and  also  lends itself well to scripted opera-
       tions.  SPLAT!'s CPU and memory scheduling priority may be
       adjusted through the use of the Unix nice command.

       The number and type of switches passed to SPLAT! determine
       its mode of operation and method of  output  data  genera-
       tion.   Nearly all of SPLAT!'s switches may be cascaded in
       any order on the command line when invoking the program to
       include  all the features described by those switches when
       performing an analysis.

POINT-TO-POINT ANALYSIS
       SPLAT! may be used to perform line-of-sight terrain analy-
       sis between two specified site locations.  For example:

       splat -t tx_site.qth -r rx_site.qth

       invokes  a terrain analysis between the transmitter speci-
       fied in tx_site.qth and receiver specified in rx_site.qth,
       and  writes  a  SPLAT!  Obstruction  Report to the current
       working directory.  The report  contains  details  of  the
       transmitter  and  receiver sites, and identifies the loca-
       tion of any obstructions detected during the analysis.  If
       an  obstruction  can  be  cleared  by  raising the receive
       antenna to a greater altitude, SPLAT!  will  indicate  the
       minimum  antenna  height required for a line-of-sight path
       to exist between the transmitter  and  receiver  locations
       specified.   If  the  antenna must be raised a significant
       amount, this determination may take some time.

       are optional when invoking the program.  SPLAT!  automati-
       cally  reads all SPLAT Data Files necessary to conduct the
       terrain analysis between the sites specified.  By default,
       the  location of SDF files is assumed to be in the current
       working directory unless a ".splat_path" file  is  present
       under the user's home directory.  If this file is present,
       it must contain the full directory path to the location of
       all the SDF files required by SPLAT! to perform its analy-
       sis for the region containing the transmitter and receiver
       sites  specified.   The  path  in this file must be of the
       form of a single line of ASCII text:

       /opt/splat/sdf/

       and may be generated with any text  editor.   The  default
       path  specified in the $HOME/.splat_path file may be over-
       ridden at any time using the -d switch:

       splat -t tx_site -r rx_site -d /cdrom/sdf/

       A graph of the terrain profile between  the  receiver  and
       transmitter  locations  as a function of distance from the
       receiver can be generated by adding the -p switch:

       splat -t tx_site -r rx_site -p terrain_profile.gif

       SPLAT! invokes gnuplot when generating graphs.  The  file-
       name  extension  specified to SPLAT! determines the format
       of the graph produced.  .gif will produce a 640x480  color
       GIF  graphic  file,  while .ps or .postscript will produce
       postscript output.  Output in formats such as  PNG,  Adobe
       Illustrator,  AutoCAD  dxf,  LaTeX,  and  many  others are
       available.  Please consult gnuplot, and gnuplot's documen-
       tation for details on all the supported output formats.

       A graph of elevations subtended by the terrain between the
       receiver and transmitter as a function  of  distance  from
       the receiver can be generated by using the -e switch:

       splat -t tx_site -r rx_site -e elevation_profile.gif

       The  graph produced using this switch illustrates the ele-
       vation and depression angles resulting  from  the  terrain
       between  the  receiver's location and the transmitter site
       from the perspective of the receiver's location.  A second
       trace  is  plotted  between  the  left  side  of the graph
       (receiver's location) and the location of the transmitting
       antenna  on  the right.  This trace illustrates the eleva-
       tion angle required for  a  line-of-sight  path  to  exist
       between  the  receiver  and transmitter locations.  If the
       trace intersects the elevation profile at any point on the
       graph,  then  this  is  an indication that a line-of-sight
       path does not exist under the conditions  given,  and  the
       obstructions can be clearly identified on the graph at the
       point(s) of intersection.

       A graph illustrating terrain height referenced to a  line-
       of-sight  path between the transmitter and receiver may be
       generated using the -h switch:

       splat -t tx_site -r rx_site -h height_profile.gif

       The Earth's curvature is  clearly  evident  when  plotting
       height profiles.

       A  graph  showing  Longley-Rice  path  loss may be plotted
       using the -l switch:

       splat -t tx_site -r rx_site -l path_loss_profile.gif

       When performing path loss profiles, a  Longley-Rice  Model
       Path  Loss  Report is generated by SPLAT! in the form of a
       text file with a .lro filename extension.  The report con-
       tains  bearings  and distances between the transmitter and
       receiver, as well as the Longley-Rice path loss for  vari-
       ous  distances  between the transmitter and receiver loca-
       tions.  The mode of propagation for points along the  path
       are  given  as Line-of-Sight, Single Horizon, Double Hori-
       zon, Diffraction Dominant, and Troposcatter Dominant.

       To determine the signal-to-noise  (SNR)  ratio  at  remote
       location  where random Johnson (thermal) noise is the pri-
       mary limiting factor in reception:

       SNR=T-NJ-L+G-NF

       where T is the ERP of the transmitter in dBW, NJ is  John-
       son  Noise  in dBW (-136 dBW for a 6 MHz TV channel), L is
       the path loss provided by SPLAT! in dB (as a positive num-
       ber),  G is the receive antenna gain in dB over isotropic,
       and NF is the receiver noise figure in dB.

       T may be computed as follows:

       T=TI+GT

       where TI is actual amount of RF  power  delivered  to  the
       transmitting  antenna  in  dBW,  GT  is  the  transmitting
       antenna gain (over isotropic)  in  the  direction  of  the
       receiver (or the horizon if the receiver is over the hori-
       zon).

       To compute how much more signal is available over the min-
       imum  to  necessary  to achieve a specific signal-to-noise
       ratio:

       Signal_Margin=SNR-S

       where S is the minimum desired SNR ratio (15.5 dB for ATSC
       DTV, 42 dB for analog NTSC television).

       A  topographic map may be generated by SPLAT! to visualize
       the path between the transmitter and receiver  sites  from
       yet  another  perspective.   Topographic maps generated by
       SPLAT! display elevations using a  logarithmic  grayscale,
       with higher elevations represented through brighter shades
       of gray.  The dynamic range of the image is scaled between
       the highest and lowest elevations present in the map.  The
       only exception to this is sea-level, which is  represented
       in blue.

       SPLAT!  generated  topographic  maps  are 24-bit TrueColor
       Portable PixMap (PPM) images, and may be  viewed,  edited,
       or  converted  to  other  graphic formats by popular image
       viewing applications such as xv,  The  GIMP,  ImageMagick,
       and XPaint.  PNG format is highly recommended for lossless
       compressed storage of SPLAT!  generated topographic output
       files.   An excellent command-line utility capable of con-
       verting SPLAT! PPM graphic files to PNG files is wpng, and
       is                      available                      at:
       http://www.libpng.org/pub/png/book/sources.html.    As   a
       last  resort,  PPM files may be compressed using the bzip2
       utility, and read directly by The  GIMP  in  this  format.
       Topographic output is specified using the -o switch:

       splat -t tx_site -r rx_site -o topo_map.ppm

       The  .ppm  extension  on the output filename is assumed by
       SPLAT!, and is optional.

       In this example, topo_map.ppm will  illustrate  the  loca-
       tions of the transmitter and receiver sites specified.  In
       addition, the great circle path between the two sites will
       be  drawn  over  locations  for which an unobstructed path
       exists to the transmitter at a  receiving  antenna  height
       equal   to   that  of  the  receiver  site  (specified  in
       rx_site.qth).

       It may desirable to  populate  the  topographic  map  with
       names  and  locations  of  cities,  tower  sites, or other
       important locations.  A city file may be passed to  SPLAT!
       using the -s switch:

       splat -t tx_site -r rx_site -s cities.dat -o topo_map

       Up  to five separate city files may be passed to SPLAT! at
       a time following the -s switch.

       County and state boundaries may be added  to  the  map  by
       specifying  up  to  five  U.S.  Census Bureau cartographic
       boundary files using the -b switch:

       splat -t tx_site -r rx_site -b co34_d00.dat -o topo_map

       In situations where multiple transmitter sites are in use,
       as  many as four site locations may be passed to SPLAT! at
       a time for analysis:

       splat -t tx_site1 tx_site2 tx_site3 tx_site4 -r rx_site -p
       profile.gif

       In  this  example,  four  separate  terrain  profiles  and
       obstruction reports will be generated by SPLAT!.  A single
       topographic  map can be specified using the -o switch, and
       line-of-sight  paths  between  each  transmitter  and  the
       receiver  site indicated will be produced on the map, each
       in its own color.  The path between the first  transmitter
       specified  to  the  receiver  will  be  in green, the path
       between the second transmitter and the receiver will be in
       cyan,  the  path  between  the  third  transmitter and the
       receiver will be in  violet,  and  the  path  between  the
       fourth transmitter and the receiver will be in sienna.

DETERMINING REGIONAL COVERAGE
       SPLAT! can analyze a transmitter or repeater site, or net-
       work of sites, and predict the regional coverage for  each
       site specified.  In this mode, SPLAT! can generate a topo-
       graphic map displaying the geometric line-of-sight  cover-
       age  area of the sites based on the location of each site,
       and the height of receive antenna wishing  to  communicate
       with the site in question.  SPLAT! switches from point-to-
       point analysis mode to area prediction mode  when  the  -c
       switch is invoked as follows:

       splat  -t tx_site -c 30.0 -s cities.dat -b co34_d00.dat -o
       tx_coverage

       In this example, SPLAT! generates a topographic map called
       tx_coverage.ppm  that  illustrates  the predicted line-of-
       sight regional coverage of tx_site to receiving  locations
       having  antennas  30.0 feet above ground level (AGL).  The
       contents of cities.dat are plotted on the map, as are  the
       cartographic    boundaries    contained    in   the   file
       co34_d00.dat.

       When plotting line-of-sight paths and  areas  of  regional
       coverage,  SPLAT!  by  default  does  not  account for the
       effects of atmospheric bending.   However,  this  behavior
       may  be modified by using the Earth radius multiplier (-m)
       switch:

       splat -t wnjt -c 30.0 -m  1.333  -s  cities.dat  -b  coun-
       ties.dat -o map.ppm

       An  earth  radius multiplier  of 1.333 instructs SPLAT! to
       use the "four-thirds earth" model for line-of-sight propa-
       gation  analysis.  Any appropriate earth radius multiplier
       may be selected by the user.

       When invoked in area prediction mode, SPLAT!  generates  a
       site  report  for  each  station  analyzed.   SPLAT!  site
       reports contain details of the site's geographic location,
       its  height  above  mean  sea  level, the antenna's height
       above mean sea level, the antenna's height  above  average
       terrain,  and the height of the average terrain calculated
       in the directions of 0, 45, 90, 135, 180,  225,  270,  and
       315 degrees azimuth.

       If  the  -c  switch is replaced by a -L switch, a Longley-
       Rice path loss map for a transmitter site  may  be  gener-
       ated:

       splat  -t tx_site -L 30.0 -s cities.dat -b co34_d00.dat -o
       path_loss_map

       In this mode, SPLAT! generates a  multi-color  map  illus-
       trating  expected  signal levels (path loss) in areas sur-
       rounding the transmitter site.  A legend at the bottom  of
       the  map  correlates  each color with a specific path loss
       level in decibels.  Since Longley-Rice area prediction map
       generation  is quite CPU intensive, provision for limiting
       the analysis range is provided  by  the  -R  switch.   The
       argument  must  be  given in miles.  If a range wider than
       the generated topographic map is  specified,  SPLAT!  will
       perform  Longley-Rice  path  loss calculations between all
       four corners of the area prediction map.

DETERMINING MULTIPLE REGIONS OF COVERAGE
       SPLAT! can also display line-of-sight coverage  areas  for
       as  many  as  four  separate transmitter sites on a common
       topographic map.  For example:

       splat -t site1 site2 site3 site4 -c 30.0 -o network.ppm

       plots the regional line-of-sight coverage of site1, site2,
       site3,  and  site4 based on a receive antenna located 30.0
       feet above ground level.  A topographic map is then  writ-
       ten  to  the file network.ppm.  The line-of-sight coverage
       area of the transmitters are plotted  as  follows  in  the
       colors  indicated (along with their corresponding RGB val-
       ues in decimal):

           site1: Green (0,255,0)
           site2: Cyan (0,255,255)
           site3: Medium Violet (147,112,219)
           site4: Sienna 1 (255,130,71)

           site1 + site2: Yellow (255,255,0)
           site1 + site3: Pink (255,192,203)
           site1 + site4: Green Yellow (173,255,47)
           site2 + site3: Orange (255,165,0)
           site2 + site4: Dark Sea Green 1 (193,255,193)
           site3 + site4: Dark Turquoise (0,206,209)

           site1 + site2 + site3: Dark Green (0,100,0)
           site1 + site2 + site4: Blanched Almond (255,235,205)
           site1 + site3 + site4: Medium Spring Green (0,250,154)
           site2 + site3 + site4: Tan (210,180,140)

           site1 + site2 + site3 + site4: Gold2 (238,201,0)

       If  separate .qth files are generated, each representing a
       common site location but a  different  antenna  height,  a
       single  topographic map illustrating the regional coverage
       from as many as four separate locations on a single  tower
       may be generated by SPLAT!.

TOPOGRAPHIC MAP GENERATION
       In  certain  situations, it may be desirable to generate a
       topographic map of  a  region  without  plotting  coverage
       areas,  line-of-sight  paths,  or  generating  obstruction
       reports.  There are several ways of doing  this.   If  one
       wishes  to  generate  a  topographic  map illustrating the
       location of a transmitter and receiver site along  with  a
       brief  text  report describing the locations and distances
       between the sites, the -n switch should be invoked as fol-
       lows:

       splat -t tx_site -r rx_site -n -o topo_map.ppm

       If no text report is desired, then the -N switch is used:

       splat -t tx_site -r rx_site -N -o topo_map.ppm

       If  the  -o  switch  and  output filename are omitted when
       using either the -n or -N switches, output is written to a
       file  named  map.ppm  in  the current working directory by
       default.

DETERMINATION OF ANTENNA HEIGHT ABOVE AVERAGE TERRAIN
       SPLAT! determines antenna  height  above  average  terrain
       (HAAT)  according to the procedure defined by Federal Com-
       munications Commission Part 73.313(d).  According to  this
       definition, terrain elevations along eight radials between
       2 and 10 miles (3 and 16 kilometers) from the  site  being
       analyzed  are  sampled and averaged for each 45 degrees of
       azimuth starting with True North.  If one or more  radials
       lie  entirely  over water, or over land outside the United
       States (areas for which no USGS topography data is  avail-
       able), then those radials are omitted from the calculation
       of average terrain.  If part of a radial  extends  over  a
       body of water or over land outside the United States, then
       only that part of the radial lying over United States land
       is used in the determination of average terrain.

       When  performing  point-to-point  terrain analysis, SPLAT!
       determines the antenna height above average  terrain  only
       if  enough topographic data has already been loaded by the
       program to perform the point-to-point analysis.   In  most
       cases, this will be true, unless the site in question does
       not lie within 10 miles of the boundary of the  topography
       data in memory.

       When  performing area prediction analysis, enough topogra-
       phy data is normally loaded by SPLAT! to  perform  average
       terrain  calculations.  Under such conditions, SPLAT! will
       provide the antenna height above average terrain  as  well
       as  the  average terrain above mean sea level for azimuths
       of 0, 45, 90, 135, 180, 225, 270,  and  315  degrees,  and
       include such information in the site report generated.  If
       one or more of the eight radials surveyed fall over  water
       or  land outside the United States, SPLAT! reports No Ter-
       rain for those radial paths.

SETTING THE MAXIMUM SIZE OF AN ANALYSIS REGION
       SPLAT! reads SDF files into a series of memory "slots"  as
       required within the structure of the program.  Each "slot"
       holds one SDF file.  Each SDF file represents a one degree
       by  one  degree  region  of  terrain.   A #define MAXSLOTS
       statement in the first several lines of splat.cpp sets the
       maximum  number  of "slots" available for topography data.
       It also sets the maximum size of the topographic maps gen-
       erated  by  SPLAT!.   MAXSLOTS is set to 9 by default.  If
       SPLAT! produces a segmentation fault on start-up with this
       default,  it  is  an indication that not enough RAM and/or
       virtual memory (swap space) are available  to  run  SPLAT!
       with  this number of MAXSLOTS.  In this case, MAXSLOTS may
       be reduced to 4, although this will greatly limit the max-
       imum  region  SPLAT!  will  be  able  to  analyze.  If 118
       megabytes or more of total memory (swap space plus RAM) is
       available,  then  MAXSLOTS  may  be increased to 16.  This
       will permit operation over a 4-degree by 4-degree  region,
       which  is  sufficient for single antenna heights in excess
       of 10,000 feet above mean  sea  level,  or  point-to-point
       distances of over 1000 miles.

ADDITIONAL INFORMATION
       Invoking SPLAT! without any arguments will display all the
       command-line options available with the program along with
       a brief summary of each.

       The  latest news and information regarding SPLAT! software
       is available through the official SPLAT! software web page
       located at: http://www.qsl.net/kd2bd/splat.html.

FILES
       $HOME/.splat_path
              User-generated  file containing the default path to
              the directory containing the SDF data files.

       splat.lrp
              Default Longley-Rice model parameters.

AUTHORS
       John A. Magliacane, KD2BD <kd2bd@amsat.org>
              Creator, Lead Developer

       Doug McDonald <mcdonald@scs.uiuc.edu>
              Longley-Rice Model integration



KD2BD Software           20 January 2004                SPLAT!(1)
