Imported Upstream version 1.2.1

[debian/splat] / docs / english / man / splat.man

.TH SPLAT! 1 "16 September 2007" "KD2BD Software" "KD2BD Software"
.SH NAME
splat \- An RF \fBS\fPignal \fBP\fPropagation, \fBL\fPoss, \fBA\fPnd \fBT\fPerrain analysis tool
.SH SYNOPSIS
splat [-t  \fItransmitter_site.qth\fP]
[-r \fIreceiver_site.qth\fP]
[-c \fIrx antenna height for LOS coverage analysis (feet/meters) (float)\fP]
[-L \fIrx antenna height for Longley-Rice coverage analysis (feet/meters) (float)\fP]
[-p \fIterrain_profile.ext\fP]
[-e \fIelevation_profile.ext\fP]
[-h \fIheight_profile.ext\fP]
[-H \fInormalized_height_profile.ext\fP]
[-l \fILongley-Rice_profile.ext\fP]
[-o \fItopographic_map_filename.ppm\fP]
[-b \fIcartographic_boundary_filename.dat\fP]
[-s \fIsite/city_database.dat\fP]
[-d \fIsdf_directory_path\fP]
[-m \fIearth radius multiplier (float)\fP]
[-f \fIfrequency (MHz) for Fresnel zone calculations (float)\fP]
[-R \fImaximum coverage radius (miles/kilometers) (float)\fP]
[-dB \fImaximum attenuation contour to display on path loss maps (80-230 dB)\fP]
[-fz \fIFresnel zone clearance percentage (default = 60)\fP]
[-plo \fIpath_loss_output_file.txt\fP]
[-pli \fIpath_loss_input_file.txt\fP]
[-udt \fIuser_defined_terrain_file.dat\fP]
[-n]
[-N]
[-nf]
[-ngs]
[-geo]
[-kml]
[-metric]
.SH DESCRIPTION
\fBSPLAT!\fP is a powerful terrestrial RF propagation and terrain
analysis tool for the spectrum between 20 MHz and 20 GHz.
\fBSPLAT!\fP is free software, and is designed for operation on Unix
and Linux-based workstations.  Redistribution and/or modification
is permitted under the terms of the GNU General Public License, Version 2,
as published by the Free Software Foundation.  Adoption of \fBSPLAT!\fP
source code in proprietary or closed-source applications is a violation
of this license and is \fBstrictly\fP forbidden. 

\fBSPLAT!\fP is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.
.SH INTRODUCTION
Applications of \fBSPLAT!\fP include the visualization, design, and
link budget analysis of wireless Wide Area Networks (WANs), commercial
and amateur radio communication systems above 20 MHz, microwave links,
frequency coordination and interference studies, and the prediction
of analog and digital terrestrial radio and television contour regions.

\fBSPLAT!\fP provides RF site engineering data such as great circle
distances and bearings between sites, antenna elevation angles (uptilt),
depression angles (downtilt), antenna height above mean sea level,
antenna height above average terrain, bearings, distances, and elevations
to known obstructions, Longley-Rice path attenuation, and received signal
strength.  In addition, the minimum antenna height requirements needed to
clear terrain, the first Fresnel zone, and any user-definable percentage
of the first Fresnel zone are also provided.

\fBSPLAT!\fP produces reports, graphs, and high resolution topographic
maps that depict line-of-sight paths, and regional path loss and signal
strength contours through which expected coverage areas of transmitters
and repeater systems can be obtained.  When performing line-of-sight
and Longley-Rice analyses in situations where multiple transmitter or
repeater sites are employed, \fBSPLAT!\fP determines individual and
mutual areas of coverage within the network specified.

Simply typing \fCsplat\fR on the command line will return a summary
of \fBSPLAT!\fP's command line options:
\fC

             --==[ SPLAT! v1.2.1 Available Options... ]==--

     -t txsite(s).qth (max of 4 with -c, max of 30 with -L)
     -r rxsite.qth
     -c plot coverage of TX(s) with an RX antenna at X feet/meters AGL
     -L plot path loss map of TX based on an RX at X feet/meters AGL
     -s filename(s) of city/site file(s) to import (5 max)
     -b filename(s) of cartographic boundary file(s) to import (5 max)
     -p filename of terrain profile graph to plot
     -e filename of terrain elevation graph to plot
     -h filename of terrain height graph to plot
     -H filename of normalized terrain height graph to plot
     -l filename of Longley-Rice graph to plot
     -o filename of topographic map to generate (.ppm)
     -u filename of user-defined terrain file to import
     -d sdf file directory path (overrides path in ~/.splat_path file)
     -m earth radius multiplier
     -n do not plot LOS paths in .ppm maps
     -N do not produce unnecessary site or obstruction reports
     -f frequency for Fresnel zone calculation (MHz)
     -R modify default range for -c or -L (miles/kilometers)
    -db maximum loss contour to display on path loss maps (80-230 dB)
    -nf do not plot Fresnel zones in height plots
    -fz Fresnel zone clearance percentage (default = 60)
   -ngs display greyscale topography as white in .ppm files
   -erp override ERP in .lrp file (Watts)
   -pli filename of path-loss input file
   -plo filename of path-loss output file
   -udt filename of user defined terrain input file
   -kml generate Google Earth (.kml) compatible output
   -geo generate an Xastir .geo georeference file (with .ppm output)
-metric employ metric rather than imperial units for all user I/O
\fR
.SH INPUT FILES
\fBSPLAT!\fP is a command-line driven application and reads input
data through a number of data files.  Some files are mandatory for
successful execution of the program, while others are optional.
Mandatory files include 3-arc second topography models in the
form of SPLAT Data Files (SDF files), site location files (QTH
files), and Longley-Rice model parameter files (LRP files).
Optional files include city location files, cartographic boundary
files, user-defined terrain files, path-loss input files, antenna
radiation pattern files, and color definition files.
.SH SPLAT DATA FILES
\fBSPLAT!\fP imports topographic data in the form of SPLAT Data Files
(SDFs).  These files may be generated from a number of information sources.
In the United States, SPLAT Data Files can be generated through U.S.
Geological Survey Digital Elevation Models (DEMs) using the \fBusgs2sdf\fP
utility included with \fBSPLAT!\fP.  USGS Digital Elevation Models
compatible with this utility may be downloaded from:
\fIhttp://edcftp.cr.usgs.gov/pub/data/DEM/250/\fP.

Significantly better resolution and accuracy can be obtained through
the use of SRTM-3 Version 2 digital elevation models.  These models are
the product of the STS-99 Space Shuttle Radar Topography Mission, and
are available for most populated regions of the Earth.  SPLAT Data Files
may be generated from SRTM data using the included \fBsrtm2sdf\fP utility.
SRTM-3 Version 2 data may be obtained through anonymous FTP from:
\fIftp://e0srp01u.ecs.nasa.gov:21/srtm/version2/\fP

The \fBstrm2sdf\fP utility may also be used to convert 3-arc second SRTM
data in Band Interleaved by Line (.BIL) format for use with \fBSPLAT!\fP.
This data is available via the web at:
\fIhttp://seamless.usgs.gov/website/seamless/\fP

Band Interleaved by Line data must be downloaded in a very specific manner
to be compatible with \fBsrtm2sdf\fP and \fBSPLAT!\fP.  Please consult
\fBsrtm2sdf\fP's documentation for instructions on downloading .BIL
topographic data through the USGS's Seamless Web Site.

Despite the higher accuracy that SRTM data has to offer, some voids
in the data sets exist.  When voids are detected, the \fBsrtm2sdf\fP
utility replaces them with corresponding data found in existing SDF
files (that were presumably created from earlier USGS data through the
\fBusgs2sdf\fP utility).  If USGS-derived SDF data is not available, voids
are handled through adjacent pixel averaging, or direct replacement.

SPLAT Data Files contain integer value topographic elevations (in meters)
referenced to 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 (\fI.sdf\fP) as generated by the \fBusgs2sdf\fP
and \fBsrtm2sdf\fP utilities, or in bzip2 compressed format
(\fI.sdf.bz2\fP).  Since uncompressed files can be read slightly
faster than files that have been compressed, \fBSPLAT!\fP searches for
needed SDF data in uncompressed format first.  If uncompressed data
cannot be located, \fBSPLAT!\fP then searches for data in bzip2 compressed
format.  If no compressed SDF files can be found for the region requested,
\fBSPLAT!\fP assumes the region is over water, and will assign an
elevation of sea-level to these areas.

This feature of \fBSPLAT!\fP makes it possible to perform path analysis
not only over land, but also between coastal areas not represented by
Digital Elevation Model data.  However, this behavior of \fBSPLAT!\fP
underscores the importance of having all the SDF files required for
the region being analyzed if meaningful results are to be expected.
.SH SITE LOCATION (QTH) FILES
\fBSPLAT!\fP imports site location information of transmitter and receiver
sites analyzed by the program from ASCII files having a \fI.qth\fP extension.
QTH files contain the site's name, the site's latitude (positive if North
of the equator, negative if South), the site's longitude (in degrees West,
0 to 360 degrees, or degrees East 0 to -360 degrees), and the site's
antenna height above ground level (AGL), each separated by a single
line-feed character.  The antenna height is assumed to be specified in
feet unless followed by the letter \fIm\fP or the word \fImeters\fP in
either upper or lower case.  Latitude and longitude information may be
expressed in either decimal format (74.6864) or degree, minute, second
(DMS) format (74 41 11.0).

For example, a site location file describing television station WNJT-DT,
Trenton, NJ (\fIwnjt-dt.qth\fP) might read as follows:
\fC
        WNJT-DT
        40.2828
        74.6864
        990.00
\fR
Each transmitter and receiver site analyzed by \fBSPLAT!\fP must be
represented by its own site location (QTH) file.
.SH LONGLEY-RICE PARAMETER (LRP) FILES
Longley-Rice parameter data files are required for \fBSPLAT!\fP to
determine RF path loss in either point-to-point or area prediction
mode.  Longley-Rice model parameter data is read from files having
the same base name as the transmitter site QTH file, but with a
\fI.lrp\fP extension.  \fBSPLAT!\fP LRP files share the following
format (\fIwnjt-dt.lrp\fP):
\fC
        15.000  ; Earth Dielectric Constant (Relative permittivity)
        0.005   ; Earth Conductivity (Siemens per meter)
        301.000 ; Atmospheric Bending Constant (N-units)
        647.000 ; Frequency in MHz (20 MHz to 20 GHz)
        5       ; Radio Climate (5 = Continental Temperate)
        0       ; Polarization (0 = Horizontal, 1 = Vertical)
        0.50    ; Fraction of situations (50% of locations)
        0.90    ; Fraction of time (90% of the time)
        46000.0 ; ERP in Watts (optional)
\fR
If an LRP file corresponding to the tx_site QTH file cannot
be found, \fBSPLAT!\fP scans the current working directory for
the file "splat.lrp".  If this file cannot be found, then default
parameters will be assigned by \fBSPLAT!\fP and a corresponding
"splat.lrp" file containing these default parameters will be written
to the current working directory.  The generated "splat.lrp" file can
then be edited by the user as needed.

Typical Earth dielectric constants and conductivity values are as
follows:
\fC
                           Dielectric Constant  Conductivity
        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
\fR
Radio climate codes used by \fBSPLAT!\fP are as follows:
\fC
        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
\fR
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 seventh and eighth parameters in the \fI.lrp\fP file correspond to the
statistical analysis provided by the Longley-Rice model.  In this example,
\fBSPLAT!\fP will return the maximum path loss occurring 50% of the time
(fraction of time) in 90% of situations (fraction of situations).  This is
often denoted as F(50,90) in Longley-Rice studies.  In the United States,
an F(50,90) criteria is typically used for digital television (8-level
VSB modulation), while F(50,50) is used for analog (VSB-AM+NTSC) broadcasts.

For further information on these parameters, see:
\fIhttp://flattop.its.bldrdoc.gov/itm.html\fP and
\fIhttp://www.softwright.com/faq/engineering/prop_longley_rice.html\fP

The final parameter in the \fI.lrp\fP file corresponds to the transmitter's
effective radiated power, and is optional.  If it is included in the
\fI.lrp\fP file, then \fBSPLAT!\fP will compute received signal strength
levels and field strength level contours when performing Longley-Rice
studies.  If the parameter is omitted, path loss is computed instead.
The ERP provided in the \fI.lrp\fP file can be overridden by using
\fBSPLAT!\fP's \fI-erp\fP command-line switch.  If the \fI.lrp\fP file
contains an ERP parameter and the generation of path-loss rather than
signal strength contours is desired, the ERP can be assigned to zero
using the \fI-erp\fP switch without having to edit the \fI.lrp\fP file
to accomplish the same result.
.SH CITY LOCATION FILES
The names and locations of cities, tower sites, or other points of interest
may be imported and plotted on topographic maps generated by \fBSPLAT!\fP.
\fBSPLAT!\fP imports the names of cities and locations from ASCII files
containing the location of interest's name, latitude, and longitude.
Each field is separated by a comma.  Each record is separated by a
single line feed character.  As was the case with the \fI.qth\fP
files, latitude and longitude information may be entered in either
decimal or degree, minute, second (DMS) format.

For example (\fIcities.dat\fP):
\fC
        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
\fR
A total of five separate city data files may be imported at a time,
and there is no limit to the size of these files.  \fBSPLAT!\fP reads
city data on a "first come/first served" basis, and plots only those
locations whose annotations do not conflict with annotations of
locations read earlier in the current city data file, or in previous
files.  This behavior minimizes clutter in \fBSPLAT!\fP generated
topographic maps, but also mandates that important locations be placed
toward the beginning of the first city data file, and locations less
important be positioned further down the list or in subsequent data
files.

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 \fBcitydecoder\fP utility included with
\fBSPLAT!\fP.  Such data is available free of charge via the Internet
at: \fIhttp://www.census.gov/geo/www/cob/bdy_files.html\fP, and must
be in ASCII format.
.SH CARTOGRAPHIC BOUNDARY DATA FILES
Cartographic boundary data may also be imported to plot the boundaries of
cities, counties, or states on topographic maps generated by \fBSPLAT!\fP.
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:
\fIhttp://www.census.gov/geo/www/cob/co2000.html#ascii\fP and
\fIhttp://www.census.gov/geo/www/cob/pl2000.html#ascii\fP.  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.
.SH PROGRAM OPERATION
\fBSPLAT!\fP is invoked via the command-line using a series of switches
and arguments.  Since \fBSPLAT!\fP is a CPU and memory intensive application,
this type of interface minimizes overhead and lends itself well to
scripted (batch) operations.  \fBSPLAT!\fP's CPU and memory scheduling
priority may be modified through the use of the Unix \fBnice\fP command.

The number and type of switches passed to \fBSPLAT!\fP determine its
mode of operation and method of output data generation.  Nearly all
of \fBSPLAT!\fP's switches may be cascaded in any order on the command
line when invoking the program.

\fBSPLAT!\fP operates in two distinct modes: \fIpoint-to-point mode\fP,
and \fIarea prediction mode\fP.  Either a line-of-sight (LOS) or Longley-Rice
Irregular Terrain (ITM) propagation model may be invoked by the user.  True
Earth, four-thirds Earth, or any other user-defined Earth radius may be
specified when performing line-of-sight analysis.
.SH POINT-TO-POINT ANALYSIS
\fBSPLAT!\fP may be used to perform line-of-sight terrain analysis
between two specified site locations.  For example:

\fCsplat -t tx_site.qth -r rx_site.qth\fR

invokes a line-of-sight terrain analysis between the transmitter
specified in \fItx_site.qth\fP and receiver specified in \fIrx_site.qth\fP
using a True Earth radius model, and writes a \fBSPLAT!\fP Path Analysis
Report to the current working directory.  The report contains details of
the transmitter and receiver sites, and identifies the location of any
obstructions detected along the line-of-sight path.  If an obstruction
can be cleared by raising the receive antenna to a greater altitude,
\fBSPLAT!\fP will indicate the minimum antenna height required for a
line-of-sight path to exist between the transmitter and receiver locations
specified.  Note that imperial units (miles, feet) are specified unless
the \fI-metric\fP switch is added to \fBSPLAT!\fP's command line options:

\fCsplat -t tx_site.qth -r rx_site.qth -metric\fR

If the antenna must be raised a significant amount, this determination
may take a few moments.  Note that the results provided are the \fIminimum\fP
necessary for a line-of-sight path to exist, and in the case of this
simple example, do not take Fresnel zone clearance requirements into
consideration.

\fIqth\fP extensions are assumed by \fBSPLAT!\fP for QTH files, and
are optional when specifying -t and -r arguments on the command-line.
\fBSPLAT!\fP automatically reads all SPLAT Data Files necessary to
conduct the terrain analysis between the sites specified.  \fBSPLAT!\fP
searches for the required SDF files in the current working directory
first.  If the needed files are not found, \fBSPLAT!\fP then searches
in the path specified by the \fI-d\fP command-line switch:

\fCsplat -t tx_site -r rx_site -d /cdrom/sdf/\fR

An external directory path may be specified by placing a ".splat_path"
file under the user's home directory.  This file must contain the full
directory path of last resort to all the SDF files.  The path in the
\fI$HOME/.splat_path\fP file must be of the form of a single line of
ASCII text:

\fC/opt/splat/sdf/\fR

and can be generated using any text editor.

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 \fI-p\fP switch:

\fCsplat -t tx_site -r rx_site -p terrain_profile.png\fR

\fBSPLAT!\fP invokes \fBgnuplot\fP when generating graphs.  The filename
extension specified to \fBSPLAT!\fP determines the format of the graph
produced.  \fI.png\fP will produce a 640x480 color PNG graphic file,
while \fI.ps\fP or \fI.postscript\fP will produce postscript output.
Output in formats such as GIF, Adobe Illustrator, AutoCAD dxf,
LaTeX, and many others are available.  Please consult \fBgnuplot\fP,
and \fBgnuplot\fP's documentation 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 \fI-e\fP switch:

\fCsplat -t tx_site -r rx_site -e elevation_profile.png\fR

The graph produced using this switch illustrates the elevation 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 elevation 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 \fI-h\fP switch:

\fCsplat -t tx_site -r rx_site -h height_profile.png\fR

A terrain height plot normalized to the transmitter and receiver
antenna heights can be obtained using the \fI-H\fP switch:

\fCsplat -t tx_site -r rx_site -H normalized_height_profile.png\fR

A contour of the Earth's curvature is also plotted in this mode.

The first Fresnel Zone, and 60% of the first Fresnel Zone can be
added to height profile graphs by adding the \fI-f\fP switch, and
specifying a frequency (in MHz) at which the Fresnel Zone should be
modeled:

\fCsplat -t tx_site -r rx_site -f 439.250 -H normalized_height_profile.png\fR

Fresnel Zone clearances other 60% can be specified using the \fI-fz\fP
switch as follows:

\fCsplat -t tx_site -r rx_site -f 439.250 -fz 75 -H height_profile2.png\fR

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

\fCsplat -t tx_site -r rx_site -l path_loss_profile.png\fR

As before, adding the \fI-metric\fP switch forces the graphs to
be plotted using metric units of measure.

When performing a point-to-point analysis, a \fBSPLAT!\fP Path Analysis
Report is generated in the form of a text file with a \fI.txt\fP filename
extension.  The report contains bearings and distances between the
transmitter and receiver, as well as the free-space and Longley-Rice
path loss for the path being analyzed.  The mode of propagation for
the path is given as \fILine-of-Sight\fP, \fISingle Horizon\fP,
\fIDouble Horizon\fP, \fIDiffraction Dominant\fP, or \fITroposcatter
Dominant\fP.

Distances and locations to known obstructions along the path
between transmitter and receiver are also provided.  If the
transmitter's effective radiated power is specified in the
transmitter's corresponding \fI.lrp\fP file, then predicted
signal strength and antenna voltage at the receiving location
is also provided in the Path Analysis Report.

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

.EQ
SNR = T - NJ - L + G - NF
.EN

where \fBT\fP is the ERP of the transmitter in dBW in the direction
of the receiver, \fBNJ\fP is Johnson Noise in dBW (-136 dBW for a 6 MHz
television channel), \fBL\fP is the path loss provided by \fBSPLAT!\fP
in dB (as a \fIpositive\fP number), \fBG\fP is the receive antenna gain
in dB over isotropic, and \fBNF\fP is the receiver noise figure in dB.

\fBT\fP may be computed as follows:

.EQ
T = TI + GT
.EN

where \fBTI\fP is actual amount of RF power delivered to the transmitting
antenna in dBW, \fBGT\fP is the transmitting antenna gain (over isotropic)
in the direction of the receiver (or the horizon if the receiver is over
the horizon).

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

.EQ
Signal_Margin = SNR - S
.EN

where \fBS\fP is the minimum required SNR ratio (15.5 dB for
ATSC (8-level VSB) DTV, 42 dB for analog NTSC television).

A topographic map may be generated by \fBSPLAT!\fP to visualize the
path between the transmitter and receiver sites from yet another
perspective.  Topographic maps generated by \fBSPLAT!\fP 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 using the color blue.

Topographic output is invoked using the \fI-o\fP switch:

\fCsplat -t tx_site -r rx_site -o topo_map.ppm\fR

The \fI.ppm\fP extension on the output filename is assumed by
\fBSPLAT!\fP, and is optional.

In this example, \fItopo_map.ppm\fP will illustrate the locations 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 \fIrx_site.qth\fP).

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 \fBSPLAT!\fP using the \fI-s\fP switch:

\fCsplat -t tx_site -r rx_site -s cities.dat -o topo_map\fR

Up to five separate city files may be passed to \fBSPLAT!\fP at a time
following the \fI-s\fP 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 \fI-b\fP
switch:

\fCsplat -t tx_site -r rx_site -b co34_d00.dat -o topo_map\fR

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

\fCsplat -t tx_site1 tx_site2 tx_site3 tx_site4 -r rx_site -p profile.png\fR

In this example, four separate terrain profiles and obstruction reports
will be generated by \fBSPLAT!\fP.  A single topographic map can be
specified using the \fI-o\fP 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.

\fBSPLAT!\fP generated topographic maps are 24-bit TrueColor Portable
PixMap (PPM) images.  They may be viewed, edited, or converted to other
graphic formats by popular image viewing applications such as \fBxv\fP,
\fBThe GIMP\fP, \fBImageMagick\fP, and \fBXPaint\fP.  PNG format is
highly recommended for lossless compressed storage of \fBSPLAT!\fP
generated topographic output files.  \fBImageMagick\fP's command-line
utility easily converts \fBSPLAT!\fP's PPM files to PNG format:

\fCconvert splat_map.ppm splat_map.png\fR

Another excellent PPM to PNG command-line utility is available
at: \fIhttp://www.libpng.org/pub/png/book/sources.html\fP.  As a last
resort, PPM files may be compressed using the bzip2 utility, and read
directly by \fBThe GIMP\fP in this format.

The \fI-ngs\fP option assigns all terrain to the color white, and can be
used when it is desirable to generate a map that is devoid of terrain:

\fCsplat -t tx_site -r rx_site -b co34_d00.dat -ngs -o white_map\fR

The resulting .ppm image file can be converted to .png format with a
transparent background using \fBImageMagick\fP's \fBconvert\fP utility:

\fCconvert -transparent "#FFFFFF" white_map.ppm transparent_map.png\fR
.SH REGIONAL COVERAGE ANALYSIS
\fBSPLAT!\fP can analyze a transmitter or repeater site, or network
of sites, and predict the regional coverage for each site specified.
In this mode, \fBSPLAT!\fP can generate a topographic map displaying
the geometric line-of-sight coverage 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.  A regional analysis may be
performed by \fBSPLAT!\fP using the \fI-c\fP switch as follows:

\fCsplat -t tx_site -c 30.0 -s cities.dat -b co34_d00.dat -o tx_coverage\fR

In this example, \fBSPLAT!\fP generates a topographic map called
\fItx_coverage.ppm\fP that illustrates the predicted line-of-sight
regional coverage of \fItx_site\fP to receiving locations having
antennas 30.0 feet above ground level (AGL).  If the \fI-metric\fP
switch is used, the argument following the \fI-c\fP switch is
interpreted as being in meters rather than in feet.  The contents
of \fIcities.dat\fP are plotted on the map, as are the cartographic
boundaries contained in the file \fIco34_d00.dat\fP.

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

\fCsplat -t wnjt-dt -c 30.0 -m 1.333 -s cities.dat -b counties.dat -o map.ppm\fR

An earth radius multiplier of 1.333 instructs \fBSPLAT!\fP to use
the "four-thirds earth" model for line-of-sight propagation analysis.
Any appropriate earth radius multiplier may be selected by the user.
 
When performing a regional analysis, \fBSPLAT!\fP generates a
site report for each station analyzed.  \fBSPLAT!\fP 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 toward the bearings of 0, 45, 90, 135,
180, 225, 270, and 315 degrees azimuth.
.SH DETERMINING MULTIPLE REGIONS OF LOS COVERAGE
\fBSPLAT!\fP can also display line-of-sight coverage areas for as
many as four separate transmitter sites on a common topographic map.
For example:

\fCsplat -t site1 site2 site3 site4 -c 10.0 -metric -o network.ppm\fR

plots the regional line-of-sight coverage of site1, site2, site3,
and site4 based on a receive antenna located 10.0 meters above ground
level.  A topographic map is then written to the file \fInetwork.ppm\fP.
The line-of-sight coverage area of the transmitters are plotted as
follows in the colors indicated (along with their corresponding RGB
values in decimal):
\fC
    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)
\fR
If separate \fI.qth\fP 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 \fBSPLAT!\fP.
.SH LONGLEY-RICE PATH LOSS ANALYSIS 
If the \fI-c\fP switch is replaced by a \fI-L\fP switch, a
Longley-Rice path loss map for a transmitter site may be generated:

\fCsplat -t wnjt -L 30.0 -s cities.dat -b co34_d00.dat -o path_loss_map\fR

In this mode, \fBSPLAT!\fP generates a multi-color map illustrating
expected signal levels in areas surrounding the transmitter site.  A
legend at the bottom of the map correlates each color with a specific
path loss range in decibels or signal strength in decibels over one
microvolt per meter (dBuV/m).

The Longley-Rice analysis range may be modified to a user-specific
value using the \fI-R\fP switch.  The argument must be given in miles
(or kilometers if the \fI-metric\fP switch is used).  If a range wider
than the generated topographic map is specified, \fBSPLAT!\fP will
perform Longley-Rice path loss calculations between all four corners
of the area prediction map.

The \fI-db\fP switch allows a constraint to be placed on the maximum
path loss region plotted on the map.  A maximum path loss between 80
and 230 dB may be specified using this switch.  For example, if a path
loss beyond -140 dB is irrelevant to the survey being conducted,
\fBSPLAT!\fP's path loss plot can be constrained to the region
bounded by the 140 dB attenuation contour as follows:

\fCsplat -t wnjt-dt -L 30.0 -s cities.dat -b co34_d00.dat -db 140 -o plot.ppm\fR

.SH SIGNAL CONTOUR COLOR DEFINITION PARAMETERS
The colors used to illustrate signal strength and path loss contours
in \fBSPLAT!\fP generated coverage maps may be tailored by the user
by creating or modifying \fBSPLAT!\fP's color definition files.
\fBSPLAT!\fP color definition files have the same base name as the
transmitter's \fI.qth\fP file, but carry \fI.lcf\fP and \fI.scf\fP
extensions.

When a regional Longley-Rice analysis is performed and the transmitter's
ERP is not specified or is zero, a \fI.lcf\fP path loss color
definition file corresponding to the transmitter site (\fI.qth\fP) is
read by \fBSPLAT!\fP from the current working directory.  If a \fI.lcf\fP
file corresponding to the transmitter site is not found, then a default
file suitable for manual editing by the user is automatically generated
by \fBSPLAT!\fP.  If the transmitter's ERP is specified, then a signal
strength map is generated and a signal strength color definition file
(\fI.scf\fP) is read, or generated if one is not available in the current
working directory.

A path-loss color definition file possesses the following structure
(\fIwnjt-dt.lcf\fP):
\fC
 ; SPLAT! Auto-generated Path-Loss Color Definition ("wnjt-dt.lcf") File
 ;
 ; Format for the parameters held in this file is as follows:
 ;
 ;    dB: red, green, blue
 ;
 ; ...where "dB" is the path loss (in dB) and
 ; "red", "green", and "blue" are the corresponding RGB color
 ; definitions ranging from 0 to 255 for the region specified.
 ;
 ; The following parameters may be edited and/or expanded
 ; for future runs of SPLAT!  A total of 32 contour regions
 ; may be defined in this file.
 ;
 ;
  80: 255,   0,   0
  90: 255, 128,   0
 100: 255, 165,   0
 110: 255, 206,   0
 120: 255, 255,   0
 130: 184, 255,   0
 140:   0, 255,   0
 150:   0, 208,   0
 160:   0, 196, 196
 170:   0, 148, 255
 180:  80,  80, 255
 190:   0,  38, 255
 200: 142,  63, 255
 210: 196,  54, 255
 220: 255,   0, 255
 230: 255, 194, 204
\fR

If the path loss is less than 80 dB, the color Red (RGB = 255, 0, 0) is
assigned to the region.  If the path-loss is greater than or equal to
80 dB, but less than 90 db, then Dark Orange (255, 128, 0) is assigned
to the region.  Orange (255, 165, 0) is assigned to regions having a
path loss greater than or equal to 90 dB, but less than 100 dB, and
so on.  Greyscale terrain is displayed beyond the 230 dB path loss
contour.

\fBSPLAT!\fP signal strength color definition files share a very similar
structure (\fIwnjt-dt.scf\fP):
\fC
 ; SPLAT! Auto-generated Signal Color Definition ("wnjt-dt.scf") File
 ;
 ; Format for the parameters held in this file is as follows:
 ;
 ;    dBuV/m: red, green, blue
 ;
 ; ...where "dBuV/m" is the signal strength (in dBuV/m) and
 ; "red", "green", and "blue" are the corresponding RGB color
 ; definitions ranging from 0 to 255 for the region specified.
 ;
 ; The following parameters may be edited and/or expanded
 ; for future runs of SPLAT!  A total of 32 contour regions
 ; may be defined in this file.
 ;
 ;
 128: 255,   0,   0
 118: 255, 165,   0
 108: 255, 206,   0
  98: 255, 255,   0
  88: 184, 255,   0
  78:   0, 255,   0
  68:   0, 208,   0
  58:   0, 196, 196
  48:   0, 148, 255
  38:  80,  80, 255
  28:   0,  38, 255
  18: 142,  63, 255
   8: 140,   0, 128
\fR

If the signal strength is greater than or equal to 128 db over 1 microvolt
per meter (dBuV/m), the color Red (255, 0, 0) is displayed for the region.
If the signal strength is greater than or equal to 118 dbuV/m, but less than
128 dbuV/m, then the color Orange (255, 165, 0) is displayed, and so on.
Greyscale terrain is displayed for regions with signal strengths less than
8 dBuV/m.

Signal strength contours for some common VHF and UHF broadcasting services
in the United States are as follows:
\fC
       Analog Television Broadcasting
       ------------------------------
       Channels 2-6:       City Grade: >= 74 dBuV/m
                              Grade A: >= 68 dBuV/m
                              Grade B: >= 47 dBuV/m
       --------------------------------------------
       Channels 7-13:      City Grade: >= 77 dBuV/m
                              Grade A: >= 71 dBuV/m
                              Grade B: >= 56 dBuV/m
       --------------------------------------------
       Channels 14-69:   Indoor Grade: >= 94 dBuV/m
                           City Grade: >= 80 dBuV/m
                              Grade A: >= 74 dBuV/m
                              Grade B: >= 64 dBuV/m

       Digital Television Broadcasting
       -------------------------------
       Channels 2-6:       City Grade: >= 35 dBuV/m
                    Service Threshold: >= 28 dBuV/m
       --------------------------------------------
       Channels 7-13:      City Grade: >= 43 dBuV/m
                    Service Threshold: >= 36 dBuV/m
       --------------------------------------------
       Channels 14-69:     City Grade: >= 48 dBuV/m
                    Service Threshold: >= 41 dBuV/m

       NOAA Weather Radio (162.400 - 162.550 MHz)
       ------------------------------------------
                  Reliable: >= 18 dBuV/m
              Not reliable: <  18 dBuV/m
       Unlikely to receive: <  0 dBuV/m

       FM Radio Broadcasting (88.1 - 107.9 MHz)
       ----------------------------------------
       Analog Service Contour:  60 dBuV/m
       Digital Service Contour: 65 dBuV/m       
\fR

.SH ANTENNA RADIATION PATTERN PARAMETERS
Normalized field voltage patterns for a transmitting antenna's horizontal
and vertical planes are imported automatically into \fBSPLAT!\fP when a
Longley-Rice coverage analysis is performed.  Antenna pattern data is
read from a pair of files having the same base name as the transmitter
and LRP files, but with \fI.az\fP and \fI.el\fP extensions for azimuth
and elevation pattern files, respectively.  Specifications regarding
pattern rotation (if any) and mechanical beam tilt and tilt direction
(if any) are also contained within \fBSPLAT!\fP antenna pattern files.

For example, the first few lines of a \fBSPLAT!\fP azimuth pattern file
might appear as follows (\fIkvea.az\fP):
\fC
        183.0
        0       0.8950590
        1       0.8966406
        2       0.8981447
        3       0.8995795
        4       0.9009535
        5       0.9022749
        6       0.9035517
        7       0.9047923
        8       0.9060051
\fR
The first line of the \fI.az\fP file specifies the amount of azimuthal
pattern rotation (measured clockwise in degrees from True North) to be
applied by \fBSPLAT!\fP to the data contained in the \fI.az\fP file.
This is followed by azimuth headings (0 to 360 degrees) and their associated
normalized field patterns (0.000 to 1.000) separated by whitespace.

The structure of \fBSPLAT!\fP elevation pattern files is slightly different.
The first line of the \fI.el\fP file specifies the amount of mechanical
beam tilt applied to the antenna.  Note that a \fIdownward tilt\fP
(below the horizon) is expressed as a \fIpositive angle\fP, while an
\fIupward tilt\fP (above the horizon) is expressed as a \fInegative angle\fP.
This data is followed by the azimuthal direction of the tilt, separated by
whitespace.

The remainder of the file consists of elevation angles and their
corresponding normalized voltage radiation pattern (0.000 to 1.000)
values separated by whitespace.  Elevation angles must be specified
over a -10.0 to +90.0 degree range.  As was the convention with mechanical
beamtilt, \fInegative elevation angles\fP are used to represent elevations
\fIabove the horizon\fP, while \fIpositive angles\fP represents elevations
\fIbelow the horizon\fP.

For example, the first few lines a \fBSPLAT!\fP elevation pattern file
might appear as follows (\fIkvea.el\fP):
\fC
        1.1    130.0
       -10.0   0.172
       -9.5    0.109
       -9.0    0.115
       -8.5    0.155
       -8.0    0.157
       -7.5    0.104
       -7.0    0.029
       -6.5    0.109
       -6.0    0.185
\fR
In this example, the antenna is mechanically tilted downward 1.1 degrees
towards an azimuth of 130.0 degrees.

For best results, the resolution of azimuth pattern data should be
specified to the nearest degree azimuth, and elevation pattern data
resolution should be specified to the nearest 0.01 degrees.  If the
pattern data specified does not reach this level of resolution,
\fBSPLAT!\fP will interpolate the values provided to determine the
data at the required resolution, although this may result in a loss
in accuracy.

.SH IMPORTING AND EXPORTING REGIONAL PATH LOSS CONTOUR DATA
Performing a Longley-Rice coverage analysis can be a very time
consuming process, especially if the analysis is repeated repeatedly
to discover what effects changes to the antenna radiation patterns
make to the predicted coverage area.

This process can be expedited by exporting the Longley-Rice
regional path loss contour data to an output file, modifying the
path loss data externally to incorporate antenna pattern effects,
and then importing the modified path loss data back into \fBSPLAT!\fP
to rapidly produce a revised path loss map.

For example, a path loss output file can be generated by \fBSPLAT!\fP
for a receive site 30 feet above ground level over a 50 mile radius
surrounding a transmitter site to a maximum path loss of 140 dB using
the following syntax:

\fCsplat -t kvea -L 30.0 -R 50.0 -db 140 -plo pathloss.dat\fR

\fBSPLAT!\fP path loss output files often exceed 100 megabytes in size.
They contain information relating to the boundaries of region they describe
followed by latitudes (degrees North), longitudes (degrees West), azimuths,
elevations (to the first obstruction), and path loss figures (dB) for a
series of specific points that comprise the region surrounding the
transmitter site.  The first few lines of a \fBSPLAT!\fP path loss
output file take on the following appearance (\fIpathloss.dat\fP):
\fC
        119, 117    ; max_west, min_west
        35, 33      ; max_north, min_north
        34.2265434, 118.0631104, 48.171, -37.461, 67.70
        34.2270355, 118.0624390, 48.262, -26.212, 73.72
        34.2280197, 118.0611038, 48.269, -14.951, 79.74
        34.2285156, 118.0604401, 48.207, -11.351, 81.68
        34.2290077, 118.0597687, 48.240, -10.518, 83.26
        34.2294998, 118.0591049, 48.225, 23.201, 84.60
        34.2304878, 118.0577698, 48.213, 15.769, 137.84
        34.2309799, 118.0570984, 48.234, 15.965, 151.54
        34.2314720, 118.0564346, 48.224, 16.520, 149.45
        34.2319679, 118.0557632, 48.223, 15.588, 151.61
        34.2329521, 118.0544281, 48.230, 13.889, 135.45
        34.2334442, 118.0537643, 48.223, 11.693, 137.37
        34.2339401, 118.0530930, 48.222, 14.050, 126.32
        34.2344322, 118.0524292, 48.216, 16.274, 156.28
        34.2354164, 118.0510941, 48.222, 15.058, 152.65
        34.2359123, 118.0504227, 48.221, 16.215, 158.57
        34.2364044, 118.0497589, 48.216, 15.024, 157.30
        34.2368965, 118.0490875, 48.225, 17.184, 156.36
\fR
It is not uncommon for \fBSPLAT!\fP path loss files to contain as
many as 3 million or more lines of data.  Comments can be placed in
the file if they are proceeded by a semicolon character.  The \fBvim\fP
text editor has proven capable of editing files of this size.

Note as was the case in the antenna pattern files, negative elevation
angles refer to upward tilt (above the horizon), while positive angles
refer to downward tilt (below the horizon).  These angles refer to the
elevation to the receiving antenna at the height above ground level
specified using the \fI-L\fP switch \fIif\fP the path between transmitter
and receiver is unobstructed.  If the path between the transmitter
and receiver is obstructed, then the elevation angle to the first
obstruction is returned by \fBSPLAT!\fP.  This is because
the Longley-Rice model considers the energy reaching a distant point
over an obstructed path as a derivative of the energy scattered from
the top of the first obstruction, only.  Since energy cannot reach
the obstructed location directly, the actual elevation angle to that
point is irrelevant.

When modifying \fBSPLAT!\fP path loss files to reflect antenna
pattern data, \fIonly the last column (path loss)\fP should be amended
to reflect the antenna's normalized gain at the azimuth and elevation
angles specified in the file.  (At this time, programs and scripts
capable of performing this operation are left as an exercise for
the user.)

Modified path loss maps can be imported back into \fBSPLAT!\fP for
generating revised coverage maps:

\fCsplat -t kvea -pli pathloss.dat -s city.dat -b county.dat -o map.ppm\fR

\fBSPLAT!\fP path loss files can also be used for conducting coverage or
interference studies outside of \fBSPLAT!\fP.
.SH USER-DEFINED TERRAIN INPUT FILES
A user-defined terrain file is a user-generated text file containing latitudes,
longitudes, and heights above ground level of specific terrain features believed
to be of importance to the \fBSPLAT!\fP analysis being conducted, but noticeably
absent from the SDF files being used.  A user-defined terrain file is imported
into a \fBSPLAT!\fP analysis using the \fI-udt\fP switch:

\fC splat -t tx_site -r rx_site -udt udt_file.txt -o map.ppm\fR

A user-defined terrain file has the following appearance and structure:
\fC
       40.32180556, 74.1325, 100.0 meters
       40.321805, 74.1315, 300.0
       40.3218055, 74.1305, 100.0 meters
\fR
Terrain height is interpreted as being described in feet above ground
level unless followed by the word \fImeters\fP, and is added \fIon top of\fP
the terrain specified in the SDF data for the locations specified.  Be
aware that each user-defined terrain feature specified will be interpreted
as being 3-arc seconds in both latitude and longitude.  Features described 
in the user-defined terrain file that overlap previously defined features
in the file are ignored by \fBSPLAT!\fP. 
.SH SIMPLE 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 \fI-n\fP
switch should be invoked as follows:

\fCsplat -t tx_site -r rx_site -n -o topo_map.ppm\fR

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

\fCsplat -t tx_site -r rx_site -N -o topo_map.ppm\fR

If a topographic map centered about a single site out to a minimum
specified radius is desired instead, a command similar to the following
can be used:

\fCsplat -t tx_site -R 50.0 -s NJ_Cities -b NJ_Counties -o topo_map.ppm\fR

where -R specifies the minimum radius of the map in miles (or kilometers
if the \fI-metric\fP switch is used).  Note that the tx_site name and
location are not displayed in this example.  If display of this information
is desired, simply create a \fBSPLAT!\fP city file (\fI-s\fP option) and
append it to the list of command-line options illustrated above.

If the \fI-o\fP switch and output filename are omitted in these
operations, topographic output is written to a file named \fItx_site.ppm\fP
in the current working directory by default.
.SH GEOREFERENCE FILE GENERATION
Topographic, coverage (\fI-c\fP), and path loss contour (\fI-L\fP) maps
generated by \fBSPLAT!\fP may be imported into \fBXastir\fP (X Amateur
Station Tracking and Information Reporting) software by generating a
georeference file using \fBSPLAT!\fP's \fI-geo\fP switch:

\fCsplat -t kd2bd -R 50.0 -s NJ_Cities -b NJ_Counties -geo -o map.ppm\fR

The georeference file generated will have the same base name as the
\fI-o\fP file specified, but have a \fI .geo\fP extension, and permit
proper interpretation and display of \fBSPLAT!\fP's .ppm graphics in
\fBXastir\fP software.
.SH GOOGLE MAP KML FILE GENERATION
Keyhole Markup Language files compatible with \fBGoogle Earth\fP may
be generated by \fBSPLAT!\fP when performing point-to-point or regional
coverage analyses by invoking the \fI-kml\fP switch:

\fCsplat -t wnjt-dt -r kd2bd -kml\fR

The KML file generated will have the same filename structure as a
Path Analysis Report for the transmitter and receiver site names given,
except it will carry a \fI .kml\fP extension.

Once loaded into \fBGoogle Earth\fP (File --> Open), the KML file
will annotate the map display with the names of the transmitter and
receiver site locations.  The viewpoint of the image will be from the
position of the transmitter site looking towards the location of the
receiver.  The point-to-point path between the sites will be displayed
as a white line while the RF line-of-sight path will be displayed in
green.  \fBGoogle Earth\fP's navigation tools allow the user to
"fly" around the path, identify landmarks, roads, and other
featured content.

When performing regional coverage analysis, the \fI .kml\fP file
generated by \fBSPLAT!\fP will permit path loss or signal strength contours
to be layered on top of \fBGoogle Earth\fP's display in a semi-transparent
manner.  The generated \fI.kml\fP file will have the same basename as
that of the \fI.ppm\fP file normally generated.
.SH DETERMINATION OF ANTENNA HEIGHT ABOVE AVERAGE TERRAIN
\fBSPLAT!\fP determines antenna height above average terrain (HAAT)
according to the procedure defined by Federal Communications 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 available), then those radials are omitted from the calculation
of average terrain.

Note that SRTM elevation data, unlike older 3-arc second USGS data,
extends beyond the borders of the United States.  Therefore, HAAT
results may not be in full compliance with FCC Part 73.313(d)
in areas along the borders of the United States if the SDF files
used by \fBSPLAT!\fP are SRTM-derived. 

When performing point-to-point terrain analysis, \fBSPLAT!\fP 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 topography data is
normally loaded by \fBSPLAT!\fP to perform average terrain calculations.
Under such conditions, \fBSPLAT!\fP 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 generated site report.  If one or
more of the eight radials surveyed fall over water, or over regions
for which no SDF data is available, \fBSPLAT!\fP reports \fINo Terrain\fP
for the radial paths affected.
.SH RESTRICTING THE MAXIMUM SIZE OF AN ANALYSIS REGION
\fBSPLAT!\fP reads SDF files as needed into a series of memory "pages"
within the structure of the program.  Each "page" holds one SDF file
representing a one degree by one degree region of terrain.
A \fI#define MAXPAGES\fP statement in the first several lines of
\fIsplat.cpp\fP sets the maximum number of "pages" available for holding
topography data.  It also sets the maximum size of the topographic maps
generated by \fBSPLAT!\fP.  MAXPAGES is set to 9 by default.  If \fBSPLAT!\fP
produces a segmentation fault on start-up with this default, it is an indication
that not enough RAM and/or virtual memory (swap space) is available to
run \fBSPLAT!\fP with the number of MAXPAGES specified.  In situations where
available memory is low, MAXPAGES may be reduced to 4 with the understanding
that this will greatly limit the maximum region \fBSPLAT!\fP will be able
to analyze.  If 118 megabytes or more of total memory (swap space plus
RAM) is available, then MAXPAGES 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.
.SH ADDITIONAL INFORMATION
The latest news and information regarding \fBSPLAT!\fP software is
available through the official \fBSPLAT!\fP software web page located
at: \fIhttp://www.qsl.net/kd2bd/splat.html\fP.
.SH AUTHORS
.TP
John A. Magliacane, KD2BD <\fIkd2bd@amsat.org\fP>
Creator, Lead Developer
.TP
Doug McDonald <\fImcdonald@scs.uiuc.edu\fP>
Original Longley-Rice Model integration
.TP
Ron Bentley <\fIronbentley@earthlink.net\fP>
Fresnel Zone plotting and clearance determination