SPLAT!(1) KD2BD Software
SPLAT!(1)NAMEsplat An RF Signal Propagation, Loss, And Terrain analysis
toolSYNOPSISsplat [‐t transmitter_site.qth] [‐r receiver_site.qth]
[‐c rx antenna
height for LOS coverage analysis (feet/meters) (float)]
[‐L rx antenna
height for ITM coverage analysis (feet/meters)
(float)] [‐p ter‐
rain_profile.ext] [‐e elevation_profile.ext] [‐h
height_profile.ext]
[‐H normalized_height_profile.ext] [‐l
ITM_profile.ext] [‐o topo‐
graphic_map_filename.ppm] [‐b
cartographic_boundary_filename.dat] [‐s
site/city_database.dat] [‐d sdf_directory_path] [‐m earth
radius multi‐
plier (float)] [‐f frequency (MHz) for Fresnel zone
calculations
(float)] [‐R maximum coverage radius (miles/kilometers)
(float)] [‐dB
threshold beyond which contours will not be displayed]
[‐gc ground
clutter height (feet/meters) (float)] [‐fz Fresnel zone
clearance per‐
centage (default = 60)] [‐ano alphanumeric output file
name] [‐ani
alphanumeric input file name] [‐udt
user_defined_terrain_file.dat] [‐n]
[‐N] [‐nf] [‐sc] [‐dbm] [‐ngs] [‐geo] [‐kml] [‐gp‐
sav] [‐metric]
[‐olditm]
DESCRIPTION
SPLAT! is a powerful terrestrial RF propagation and
terrain analysis
tool for the spectrum between 20 MHz and 20 GHz. SPLAT!
is free soft‐
ware, and is designed for operation on Unix and Linux‐
based worksta‐
tions. Redistribution and/or modification is permitted
under the terms
of the GNU General Public License, Version 2, as pub‐
lished by the Free
Software Foundation. Adoption of SPLAT! source code in
proprietary or
closed‐source applications 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 warranty of MER‐
CHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License
for more details.
INTRODUCTION
Applications of SPLAT! include the visualization, design,
and link bud‐
get analysis of wireless Wide Area Networks (WANs), com‐
mercial and ama‐
teur radio communication systems above 20 MHz, mi‐
crowave links, fre‐
quency coordination and interference studies, and the
prediction of
analog and digital terrestrial radio and television con‐
tour regions.
SPLAT! provides RF site engineering data such as great
circle distances
and bearings between sites, antenna elevation angles (up‐
tilt), depres‐
sion angles (downtilt), antenna height above mean sea
level, antenna
height above average terrain, bearings, distances, and
elevations to
known obstructions, Irregular Terrain Model path at‐
tenuation, 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.
SPLAT! produces reports, graphs, and high resolution to‐
pographic 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 Irregular Terrain Model analyses in situations
where multiple
transmitter or repeater sites are employed, SPLAT! deter‐
mines individ‐
ual and mutual areas of coverage within the network speci‐
fied.INPUT FILES
SPLAT! is a command‐line driven application and reads
input data
through a number of data files. Some files are mandatory
for success‐
ful execution of the program, while others are option‐
al. Mandatory
files include digital elevation topography models in the
form of SPLAT
Data Files (SDF files), site location files (QTH files),
and Irregular
Terrain Model parameter files (LRP files). Optional files
include city
location files, cartographic boundary files, user‐de‐
fined terrain
files, path loss input files, antenna radiation pat‐
tern files, and
color definition files.
SPLAT DATA FILES
SPLAT! 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. Geo‐
logical Survey Digital Elevation Models (DEMs) using the
postdownload
and usgs2sdf utilities included with SPLAT!. USGS Digi‐
tal Elevation
Models compatible with these utilities may be
downloaded from:
http://edcftp.cr.usgs.gov/pub/data/DEM/250/.
Significantly better resolution and accuracy can be ob‐
tained through
the use of SRTM Version 2 digital elevation models,
especially when
supplemented by USGS‐derived SDF data. These one‐degree
by one‐degree
models are the product of the Space Shuttle STS‐99
Radar Topography
Mission, and are available for most populated regions of
the Earth.
SPLAT Data Files may be generated from 3 arc‐second
SRTM‐3 data using
the included srtm2sdf utility. SRTM‐3 Version 2 data may
be obtained
through anonymous FTP from:
ftp://e0srp01u.ecs.nasa.gov:21/srtm/ver‐
sion2/SRTM3/
Note that SRTM filenames refer to the latitude and lon‐
gitude of the
southwest corner of the topographic dataset contained
within the file.
Therefore, the region of interest must lie north and east
of the lati‐
tude and longitude provided in the SRTM filename.
The srtm2sdf utility may also be used to convert 3‐arc
second SRTM data
in Band Interleaved by Line (.BIL) format for use with
SPLAT!. This
data is available via the web at:
http://seamless.usgs.gov/web‐
site/seamless/
Band Interleaved by Line data must be downloaded in a
very specific
manner to be compatible with srtm2sdf and SPLAT!.
Please consult
srtm2sdf’s documentation for instructions on downloading
.BIL topo‐
graphic data through the USGS’s Seamless Web Site.
Even greater resolution and accuracy can be obtained by
using 1 arc‐
second SRTM‐1 Version 2 topography data. This data is
available for
the United States and its territories and possessions, and
may be down‐
loaded from:
ftp://e0srp01u.ecs.nasa.gov:21/srtm/version2/SRTM1/
High resolution SDF files for use with SPLAT! HD may be
generated from
data in this format using the srtm2sdf‐hd utility.
Despite the higher accuracy that SRTM data has to offer,
some voids in
the data sets exist. When voids are detected, the
srtm2sdf and
srtm2sdf‐hd utilities replace them with corresponding
data found in
usgs2sdf generated SDF files. If USGS‐derived SDF data is
not avail‐
able, voids are handled through adjacent pixel averag‐
ing, or direct
replacement.
SPLAT Data Files contain integer value topographic eleva‐
tions in meters
referenced to mean sea level for 1‐degree by 1‐degree
regions of the
Earth. SDF files can be read by SPLAT! in either
standard format
(.sdf) as generated directly by the usgs2sdf, srtm2sdf,
and srtm2sdf‐hd
utilities, or in bzip2 compressed format (.sdf.bz2).
Since uncom‐
pressed files can be read slightly faster than files
that have been
compressed, SPLAT! searches for needed SDF data in uncom‐
pressed format
first. If uncompressed data cannot be located, SPLAT!
then searches
for data in bzip2 compressed format. If no compressed SDF
files can be
found for the region requested, SPLAT! assumes the
region is over
water, 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 repre‐
sented by Digi‐
tal Elevation Model data. However, this behavior of
SPLAT! under‐
scores the importance of having all the SDF files re‐
quired for the
region being analyzed if meaningful results are to be ex‐
pected.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
(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 speci‐
fied in feet unless followed by the letter m or the
word meters in
either upper or lower case. Latitude and longitude infor‐
mation 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 (wnjt‐dt.qth) might read as follows:
WNJT‐DT
40.2828
74.6864
990.00
Each transmitter and receiver site analyzed by SPLAT!
must be repre‐
sented by its own site location (QTH) file.
IRREGULAR TERRAIN MODEL PARAMETER (LRP) FILES
Irregular Terrain Model Parameter data files are required
for SPLAT!
to determine RF path loss, field strength, or received
signal power
level in either point‐to‐point or area prediction mode.
Irregular Ter‐
rain Model parameter data is read from files having the
same base name
as the transmitter site QTH file, but with a .lrp exten‐
sion. SPLAT!
LRP files share the following format (wnjt‐dt.lrp):
15.000 ; Earth Dielectric Constant (Relative per‐
mittivity)
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 Temper‐
ate)
0 ; Polarization (0 = Horizontal, 1 = Verti‐
cal)
0.50 ; Fraction of situations (50% of loca‐
tions)
0.90 ; Fraction of time (90% of the time)
46000.0 ; Effective Radiated Power (ERP) in Watts
(optional)
If an LRP file corresponding to the tx_site QTH file
cannot be found,
SPLAT! scans the current working directory for the file
"splat.lrp".
If this file cannot be found, then default parameters
will be assigned
by SPLAT! and a corresponding "splat.lrp" file containing
these default
parameters will be written to the current working direc‐
tory. The gen‐
erated "splat.lrp" file can then be edited by the user as
needed.
Typical Earth dielectric constants and conductivity values
are as fol‐
lows:
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 Temper‐
ate climates.
The seventh and eighth parameters in the .lrp file cor‐
respond to the
statistical analysis provided by the ITM model. In
this example,
SPLAT! will return the maximum path loss occurring
50% of the time
(fraction of time, or Time Variability) in 90% of situa‐
tions (fraction
of situations, or Location Variability). This is of‐
ten 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‐lev‐
el VSB modula‐
tion), while F(50,50) is used for analog (VSB‐AM+NTSC)
broadcasts.
For further information on ITM propagation model param‐
eters, please
refer to: http://flattop.its.bldrdoc.gov/itm.html and
http://www.soft‐
wright.com/faq/engineering/prop_longley_rice.html
The last parameter in the .lrp file corresponds to the
transmitter’s
Effective Radiated Power (ERP), and is optional. If it
is included in
the .lrp file, then SPLAT! will compute received signal
strength levels
and field strength level contours when performing ITM
studies. If the
parameter is omitted, path loss is computed instead. The
ERP provided
in the .lrp file can be overridden by using SPLAT!’s ‐erp
command‐line
switch. If the .lrp file contains an ERP parameter and
the generation
of path loss rather than field strength contours is de‐
sired, the ERP
can be assigned to zero using the ‐erp switch without
having to edit
the .lrp file to accomplish the same result.
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
SPLAT!. SPLAT! imports the names of cities and loca‐
tions from ASCII
files containing the location of interest’s name, lati‐
tude, and longi‐
tude. 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 longitude information may be entered in ei‐
ther 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, and
there is no limit to the size of these files. SPLAT!
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 SPLAT! generated topo‐
graphic 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 citydecoder utility included
with SPLAT!.
Such data is available free of charge via the
Internet at:
http://www.census.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 topographic maps gener‐
ated 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 carto‐
graphic 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 lends it‐
self well to
scripted (batch) operations. SPLAT!’s CPU and memory
scheduling prior‐
ity may be modified through the use of the Unix nice com‐
mand.
The number and type of switches passed to SPLAT! determine
its mode of
operation and method of output data generation. Nearly
all of SPLAT!’s
switches may be cascaded in any order on the command line
when invoking
the program.
Simply typing splat on the command line will return
a summary of
SPLAT!’s command line options:
‐‐==[ SPLAT! v1.4.0 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 path loss 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 re‐
ports
‐f frequency for Fresnel zone calculation (MHz)
‐R modify default range for ‐c or ‐L (miles/kilome‐
ters)
‐sc display smooth rather than quantized contour lev‐
els
‐db threshold beyond which contours will not be dis‐
played
‐nf do not plot Fresnel zones in height plots
‐fz Fresnel zone clearance percentage (default = 60)
‐gc ground clutter height (feet/meters)
‐ngs display greyscale topography as white in .ppm
files
‐erp override ERP in .lrp file (Watts)
‐ano name of alphanumeric output file
‐ani name of alphanumeric input 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)
‐dbm plot signal power level contours rather than field
strength
‐gpsav preserve gnuplot temporary working files after
SPLAT! execution
‐metric employ metric rather than imperial units for
all user I/O
‐olditm invoke older ITM propagation model rather than the
newer ITWOM
The command‐line options for splat and splat‐hd are iden‐
tical.
SPLAT! operates in two distinct modes: point‐to‐point
mode, and area
prediction mode. Either a line‐of‐sight (LOS) or Ir‐
regular 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.
POINT‐TO‐POINT ANALYSIS
SPLAT! may be used to perform line‐of‐sight terrain
analysis between
two specified site locations. For example:
splat ‐t tx_site.qth ‐r rx_site.qth
invokes a line‐of‐sight terrain analysis between the
transmitter speci‐
fied in tx_site.qth and receiver specified in rx_site.qth
using a True
Earth radius model, and writes a SPLAT! Path Analysis
Report to the
current working directory. The report contains details of
the trans‐
mitter and receiver sites, and identifies the location of
any obstruc‐
tions detected along the line‐of‐sight path. If an ob‐
struction can be
cleared by raising the receive antenna to a greater al‐
titude, SPLAT!
will indicate the minimum antenna height required for a
line‐of‐sight
path to exist between the transmitter and receiver loca‐
tions specified.
Note that imperial units (miles, feet) are specified un‐
less the ‐metric
switch is added to SPLAT!’s command line options:
splat ‐t tx_site.qth ‐r rx_site.qth ‐metric
If the antenna must be raised a significant amount, this
determination
may take a few moments. Note that the results provided
are the minimum
necessary for a line‐of‐sight path to exist, and in the
case of this
simple example, do not take Fresnel zone clearance re‐
quirements into
consideration.
qth extensions are assumed by SPLAT! for QTH files, and
are optional
when specifying ‐t and ‐r arguments on the command‐line.
SPLAT! auto‐
matically reads all SPLAT Data Files necessary to con‐
duct the terrain
analysis between the sites specified. SPLAT!
searches for the
required SDF files in the current working directory
first. If the
needed files are not found, SPLAT! then searches in the
path specified
by the ‐d command‐line switch:
splat ‐t tx_site ‐r rx_site ‐d /cdrom/sdf/
An external directory path may be specified by placing a
".splat_path"
file under the user’s home directory. This file must con‐
tain the full
directory path of last resort to all the SDF files.
The path in the
$HOME/.splat_path file must be of the form of a single
line of ASCII
text:
/opt/splat/sdf/
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 ‐p switch:
splat ‐t tx_site ‐r rx_site ‐p terrain_profile.png
SPLAT! invokes gnuplot when generating graphs. The file‐
name extension
specified to SPLAT! determines the format of the graph
produced. .png
will produce a 640x480 color PNG graphic file, while .ps
or .postscript
will produce postscript output. Output in formats such as
GIF, Adobe
Illustrator, AutoCAD dxf, LaTeX, and many others are
available. Please
consult gnuplot, and gnuplot’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 gener‐
ated by using the ‐e switch:
splat ‐t tx_site ‐r rx_site ‐e elevation_profile.png
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 per‐
spective 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 el‐
evation angle
required for a line‐of‐sight path to exist between the
receiver and
transmitter locations. If the trace intersects the ele‐
vation 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 obstruc‐
tions can be clearly identified on the graph at the
point(s) of inter‐
section.
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.png
A terrain height plot normalized to the transmitter
and receiver
antenna heights can be obtained using the ‐H switch:
splat ‐t tx_site ‐r rx_site ‐H normalized_height_pro‐
file.png
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 ‐f switch, and
specifying a fre‐
quency (in MHz) at which the Fresnel Zone should be mod‐
eled:splat ‐t tx_site ‐r rx_site ‐f 439.250 ‐H normal‐
ized_height_profile.png
Fresnel Zone clearances other 60% can be specified using
the ‐fz switch
as follows:
splat ‐t tx_site ‐r rx_site ‐f 439.250 ‐fz 75 ‐H
height_profile2.png
A graph showing ITM path loss may be plotted using the ‐l
switch:splat ‐t tx_site ‐r rx_site ‐l path_loss_profile.png
As before, adding the ‐metric switch forces the graphs to
be plotted
using metric units of measure. The ‐gpsav switch in‐
structs SPLAT! to
preserve (rather than delete) the gnuplot working files
generated dur‐
ing SPLAT! execution, allowing the user to edit these
files and re‐run
gnuplot if desired.
When performing a point‐to‐point analysis, a SPLAT!
Path Analysis
Report is generated in the form of a text file with a
.txt filename
extension. The report contains bearings and distances
between the
transmitter and receiver, as well as the free‐space and
ITM path loss
for the path being analyzed. The mode of propagation for
the path is
given as Line‐of‐Sight, Single Horizon, Double
Horizon, Diffraction
Dominant, or Troposcatter Dominant. Additionally, if the
receiver is
located at the peak of a single obstruction or at the
peak of a second
obstruction, SPLAT! will report RX at Peak Terrain
Along Path when
operating under the ITWOM propagation model.
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 transmit‐
ter’s correspond‐
ing .lrp file, then predicted signal strength and antenna
voltage at
the receiving location is also provided in the Path Analy‐
sis Report.
To determine the signal‐to‐noise (SNR) ratio at remote
location where
random Johnson (thermal) noise is the primary limiting
factor in recep‐
tion:
SNR=T‐NJ‐L+G‐NF
where T is the ERP of the transmitter in dBW in the di‐
rection of the
receiver, NJ is Johnson Noise in dBW (‐136 dBW for a 6
MHz television
channel), L is the path loss provided by SPLAT! in dB
(as a positive
number), G is the receive antenna gain in dB over isotrop‐
ic, 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 re‐
ceiver is over
the horizon).
To compute how much more signal is available over the min‐
imum to neces‐
sary to achieve a specific signal‐to‐noise ratio:
Signal_Margin=SNR‐S
where S 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 SPLAT! to visual‐
ize the path
between the transmitter and receiver sites from yet an‐
other perspec‐
tive. Topographic maps generated by SPLAT! display eleva‐
tions using a
logarithmic grayscale, with higher elevations repre‐
sented through
brighter shades of gray. The dynamic range of the im‐
age is scaled
between the highest and lowest elevations present in the
map. The only
exception to this is sea‐level, which is represented us‐
ing the color
blue.
Topographic output is invoked 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 cir‐
cle path between the two sites will be drawn over loca‐
tions for which
an unobstructed path exists to the transmitter at a re‐
ceiving 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 loca‐
tions of cities, tower sites, or other important loca‐
tions. 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 fol‐
lowing 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.png
In this example, four separate terrain profiles and ob‐
struction 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 be‐
tween the fourth
transmitter and the receiver will be in sienna.
SPLAT! generated topographic maps are 24‐bit TrueColor
Portable PixMap
(PPM) images. They may be viewed, edited, or con‐
verted 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 topo‐
graphic output
files. ImageMagick’s command‐line utility easily converts
SPLAT!’s PPM
files to PNG format:
convert splat_map.ppm splat_map.png
Another excellent PPM to PNG command‐line utility 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.
The ‐ngs 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:splat ‐t tx_site ‐r rx_site ‐b co34_d00.dat ‐ngs ‐o
white_map
The resulting .ppm image file can be converted to .png
format with a
transparent background using ImageMagick’s convert utili‐
ty:
convert ‐transparent "#FFFFFF" white_map.ppm transpar‐
ent_map.pngREGIONAL COVERAGE ANALYSIS
SPLAT! can analyze a transmitter or repeater site, or net‐
work of sites,
and predict the regional coverage for each site speci‐
fied. In this
mode, SPLAT! can generate a topographic map displaying
the geometric
line‐of‐sight coverage area of the sites based on the lo‐
cation of each
site and the height of receive antenna wishing to commu‐
nicate with the
site in question. A regional analysis may be performed by
SPLAT! using
the ‐c switch 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_cover‐
age.ppm that illustrates the predicted line‐of‐sight re‐
gional coverage
of tx_site to receiving locations having antennas
30.0 feet above
ground level (AGL). If the ‐metric switch is used, the
argument fol‐
lowing the ‐c switch is interpreted as being in meters
rather than in
feet. 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 re‐
gional coverage,
SPLAT! by default does not account for the effects of at‐
mospheric bend‐
ing. However, this behavior may be modified by using the
Earth radius
multiplier (‐m) switch:
splat ‐t wnjt‐dt ‐c 30.0 ‐m 1.333 ‐s cities.dat ‐b
counties.dat ‐o
map.ppm
An earth radius multiplier of 1.333 instructs SPLAT! to
use the "four‐
thirds earth" model for line‐of‐sight propagation analy‐
sis. Any appro‐
priate earth radius multiplier may be selected by the us‐
er.
When performing a regional analysis, SPLAT! generates a
site report for
each station analyzed. SPLAT! site reports contain de‐
tails 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 aver‐
age terrain, and the height of the average terrain cal‐
culated toward
the bearings of 0, 45, 90, 135, 180, 225, 270, and 315 de‐
grees azimuth.DETERMINING MULTIPLE REGIONS OF LOS COVERAGE
SPLAT! can also display line‐of‐sight coverage areas for
as many as
four separate transmitter sites on a common topographic
map. For exam‐
ple:
splat ‐t site1 site2 site3 site4 ‐c 10.0 ‐metric ‐o net‐
work.ppm
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
network.ppm. The
line‐of‐sight coverage area of the transmitters are plot‐
ted as follows
in the colors indicated (along with their corresponding
RGB values 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 to‐
pographic map
illustrating the regional coverage from as many as four
separate loca‐
tions on a single tower may be generated by SPLAT!.
PATH LOSS ANALYSIS
If the ‐c switch is replaced by a ‐L switch, an ITM path
loss map for a
transmitter site may be generated:
splat ‐t wnjt ‐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 in areas surrounding the transmitter site.
A legend at
the bottom of the map correlates each color with a spe‐
cific path loss
range in decibels.
The ‐db switch allows a threshold to be set beyond which
contours will
not be plotted on the map. For example, if a path loss
beyond ‐140 dB
is irrelevant to the survey being conducted, SPLAT!’s
path loss plot
can be constrained to the region bounded by the 140 dB at‐
tenuation con‐
tour as follows:
splat ‐t wnjt‐dt ‐L 30.0 ‐s cities.dat ‐b co34_d00.dat
‐db 140 ‐o
plot.ppm
The path loss contour threshold may be expressed as ei‐
ther a positive
or negative quantity.
The path loss analysis range may be modified to a user‐
specific dis‐
tance using the ‐R switch. The argument must be given
in miles (or
kilometers if the ‐metric switch is used). If a range
wider than the
generated topographic map is specified, SPLAT! will
perform ITM path
loss calculations between all four corners of the area
prediction map.
The colors used to illustrate contour regions in SPLAT!
generated cov‐
erage maps may be tailored by the user by creating
or modifying
SPLAT!’s color definition files. SPLAT! color definition
files have
the same base name as the transmitter’s .qth file,
but carry .lcf,
.scf, and .dcf extensions. If the necessary file does not
exist in the
current working when SPLAT! is run, a file containing
default color
definition parameters that is suitable for manual editing
by the user
is written into the current directory.
When a regional ITM analysis is performed and the trans‐
mitter’s ERP is
not specified or is zero, a .lcf path loss color defini‐
tion file corre‐
sponding to the transmitter site (.qth) is read by SPLAT!
from the cur‐
rent working directory. If a .lcf file corresponding to
the transmit‐
ter site is not found, then a default file suitable for
manual editing
by the user is automatically generated by SPLAT!.
A path loss color definition file possesses the follow‐
ing structure
(wnjt‐dt.lcf):
; SPLAT! Auto‐generated Path‐Loss Color Definition
("wnjt‐dt.lcf")
File
;
; Format for the parameters held in this file is as fol‐
lows:
;
; 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 speci‐
fied.
;
; The following parameters may be edited and/or expanded
; for future runs of SPLAT! A total of 32 contour re‐
gions
; 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
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 re‐
gions 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 con‐
tour. Adding the ‐sc switch will smooth the transitions
between the
specified quantized contour levels.
FIELD STRENGTH ANALYSIS
If the transmitter’s effective radiated power (ERP) is
specified in the
transmitter’s .lrp file, or expressed on the command‐
line using the
‐erp switch, field strength contours referenced to
decibels over one
microvolt per meter (dBuV/m) rather than path loss are
produced:splat ‐t wnjt‐dt ‐L 30.0 ‐erp 46000 ‐db 30 ‐o plot.ppm
The ‐db switch can be used in this mode as before to limit
the extent
to which field strength contours are plotted. When
plotting field
strength contours, however, the argument given is inter‐
preted as being
expressed in dBuV/m.
SPLAT! field strength color definition files share a
very similar
structure to .lcf files used for plotting path loss:
; SPLAT! Auto‐generated Signal Color Definition ("wnjt‐
dt.scf") File
;
; Format for the parameters held in this file is as fol‐
lows:
;
; 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 speci‐
fied.
;
; The following parameters may be edited and/or expanded
; for future runs of SPLAT! A total of 32 contour re‐
gions
; 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
If the signal strength is greater than or equal to 128 dB
over 1 micro‐
volt per meter (dBuV/m), the color Red (255, 0, 0) is dis‐
played 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 dis‐
played, 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 ser‐
vices in the United States are as follows:
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
RECEIVED POWER LEVEL ANALYSIS
If the transmitter’s effective radiated power (ERP) is
specified in the
transmitter’s .lrp file, or expressed on the command‐
line using the
‐erp switch, and the ‐dbm switch is invoked, received pow‐
er level con‐
tours referenced to decibels over one milliwatt (dBm) are
produced:splat ‐t wnjt‐dt ‐L 30.0 ‐erp 46000 ‐dbm ‐db ‐100 ‐o
plot.ppm
The ‐db switch can be used to limit the extent to which
received power
level contours are plotted. When plotting power level
contours, the
argument given is interpreted as being expressed in dBm.
SPLAT! received power level color definition files share a
very similar
structure to the color definition files described earlier,
except that
the power levels in dBm may be either positive or neg‐
ative, and are
limited to a range between +40 dBm and ‐200 dBm:
; SPLAT! Auto‐generated DBM Signal Level Color Defi‐
nition ("wnjt‐
dt.dcf") File
;
; Format for the parameters held in this file is as fol‐
lows:
;
; dBm: red, green, blue
;
; ...where "dBm" is the received signal power level be‐
tween +40 dBm
; and ‐200 dBm, and "red", "green", and "blue" are the
corresponding
; RGB color definitions ranging from 0 to 255 for the
region speci‐
fied.
;
; The following parameters may be edited and/or expanded
; for future runs of SPLAT! A total of 32 contour re‐
gions
; may be defined in this file.
;
;
+0: 255, 0, 0
‐10: 255, 128, 0
‐20: 255, 165, 0
‐30: 255, 206, 0
‐40: 255, 255, 0
‐50: 184, 255, 0
‐60: 0, 255, 0
‐70: 0, 208, 0
‐80: 0, 196, 196
‐90: 0, 148, 255
‐100: 80, 80, 255
‐110: 0, 38, 255
‐120: 142, 63, 255
‐130: 196, 54, 255
‐140: 255, 0, 255
‐150: 255, 194, 204
ANTENNA RADIATION PATTERN PARAMETERS
Normalized field voltage patterns for a transmitting an‐
tenna’s horizon‐
tal and vertical planes are imported automatically into
SPLAT! when a
path loss, field strength, or received power level cover‐
age 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 .az and
.el extensions for azimuth and elevation pattern files,
respectively.
Specifications regarding pattern rotation (if any) and me‐
chanical beam
tilt and tilt direction (if any) are also contained
within SPLAT!
antenna pattern files.
For example, the first few lines of a SPLAT! azimuth pat‐
tern file might
appear as follows (kvea.az):
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
The first line of the .az file specifies the amount of
azimuthal pat‐
tern rotation (measured clockwise in degrees from True
North) to be
applied by SPLAT! to the data contained in the .az file.
This is fol‐
lowed by azimuth headings (0 to 360 degrees) and their as‐
sociated nor‐
malized field patterns (0.000 to 1.000) separated by
whitespace.
The structure of SPLAT! elevation pattern files is
slightly different.
The first line of the .el file specifies the amount of me‐
chanical beam
tilt applied to the antenna. Note that a downward
tilt (below the
horizon) is expressed as a positive angle, while an upward
tilt (above
the horizon) is expressed as a negative angle. This da‐
ta is followed
by the azimuthal direction of the tilt, separated by
whitespace.
The remainder of the file consists of elevation angles and
their corre‐
sponding normalized voltage radiation pattern (0.000 to
1.000) values
separated by whitespace. Elevation angles must be spec‐
ified over a
‐10.0 to +90.0 degree range. As was the convention
with mechanical
beamtilt, negative elevation angles are used to repre‐
sent elevations
above the horizon, while positive angles represents el‐
evations below
the horizon.
For example, the first few lines a SPLAT! elevation pat‐
tern file might
appear as follows (kvea.el):
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
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 da‐
ta should be
specified to the nearest degree azimuth, and elevation
pattern data
resolution should be specified to the nearest 0.01 de‐
grees. If the
pattern data specified does not reach this level of reso‐
lution, SPLAT!
will interpolate the values provided to determine the
data at the
required resolution, although this may result in a loss in
accuracy.EXPORTING AND IMPORTING REGIONAL CONTOUR DATA
Performing a regional coverage analysis based on an ITM
path analysis
can be a very time consuming process, especially if the
analysis is
performed repeatedly to discover what effects changes
to a transmit‐
ter’s antenna radiation pattern make to the predicted cov‐
erage area.
This process can be expedited by exporting the contour da‐
ta produced by
SPLAT! to an alphanumeric output (.ano) file. The data
contained in
this file can then be modified to incorporate antenna pat‐
tern effects,
and imported back into SPLAT! to quickly produce a revised
contour map.
Depending on the way in which SPLAT! is invoked, al‐
phanumeric output
files can describe regional path loss, signal
strength, or received
signal power levels.
For example, an alphanumeric output file containing path
loss informa‐
tion can be generated by SPLAT! 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 (assuming ERP is not specified in the
transmitter’s
.lrp file) using the following syntax:
splat ‐t kvea ‐L 30.0 ‐R 50.0 ‐db 140 ‐ano pathloss.dat
If ERP is specified in the .lrp file or on the command
line through the
‐erp switch, the alphanumeric output file will instead
contain pre‐
dicted field values in dBuV/m. If the ‐dBm command
line switch is
used, then the alphanumeric output file will contain
receive signal
power levels in dBm.
SPLAT! alphanumeric output files can exceed many hundreds
of megabytes
in size. They contain information relating to the
boundaries of the
region they describe followed by latitudes (degrees
North), longitudes
(degrees West), azimuths (referenced to True North), ele‐
vations (to the
first obstruction), followed by either path loss (in
dB), received
field strength (in dBuV/m), or received signal power
level (in dBm)
without regard to the transmitting antenna’s radiation
pattern.
The first few lines of a SPLAT! alphanumeric output file
could take on
the following appearance (pathloss.dat):
119, 117 ; max_west, min_west
35, 34 ; max_north, min_north
34.2265424, 118.0631096, 48.199, ‐32.747, 67.70
34.2270358, 118.0624421, 48.199, ‐19.161, 73.72
34.2275292, 118.0617747, 48.199, ‐13.714, 77.24
34.2280226, 118.0611072, 48.199, ‐10.508, 79.74
34.2290094, 118.0597723, 48.199, ‐11.806, 83.26 *
34.2295028, 118.0591048, 48.199, ‐11.806, 135.47 *
34.2299962, 118.0584373, 48.199, ‐15.358, 137.06 *
34.2304896, 118.0577698, 48.199, ‐15.358, 149.87 *
34.2314763, 118.0564348, 48.199, ‐15.358, 154.16 *
34.2319697, 118.0557673, 48.199, ‐11.806, 153.42 *
34.2324631, 118.0550997, 48.199, ‐11.806, 137.63 *
34.2329564, 118.0544322, 48.199, ‐11.806, 139.23 *
34.2339432, 118.0530971, 48.199, ‐11.806, 139.75 *
34.2344365, 118.0524295, 48.199, ‐11.806, 151.01 *
34.2349299, 118.0517620, 48.199, ‐11.806, 147.71 *
34.2354232, 118.0510944, 48.199, ‐15.358, 159.49 *
34.2364099, 118.0497592, 48.199, ‐15.358, 151.67 *
Comments can be placed in the file if they are pre‐
ceeded by a semi‐
colon. The vim text editor has proven capable of editing
files of this
size.
Note as was the case in the antenna pattern files, nega‐
tive 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 ‐L switch if the path between
transmitter and
receiver is unobstructed. If the path between the
transmitter and
receiver is obstructed, an asterisk (*) is placed on
the end of the
line, and the elevation angle returned by SPLAT! refers
the elevation
angle to the first obstruction rather than the geo‐
graphic location
specified on the line. This is done in response to the
fact that the
ITM model considers the energy reaching a distant
point over an
obstructed path to be the result of the energy scattered
over the top
of the first obstruction along the path. Since energy
cannot reach the
obstructed location directly, the actual elevation angle
to the desti‐
nation over such a path becomes irrelevant.
When modifying SPLAT! path loss files to reflect antenna
pattern data,
only the last numeric column should be amended to reflect
the antenna’s
normalized gain at the azimuth and elevation angles
specified in the
file. Programs and scripts capable of performing this
task are left as
an exercise for the user.
Modified alphanumeric output files can be imported
back into SPLAT!
for generating revised coverage maps provided that the
ERP and ‐dBm
options are used as they were when the alphanumeric
output file was
originally generated:
splat ‐t kvea ‐ani pathloss.dat ‐s city.dat ‐b county.dat
‐o map.ppm
Note that alphanumeric output files generated by splatcannot be used
with splat‐hd, or vice‐versa due to the resolution
incompatibility
between the two versions of the program. Also, each of
the three types
of alphanumeric output files are incompatible with one
another, so a
file containing path loss data cannot be imported into
SPLAT! to pro‐
duce signal strength or received power level contours,
etc.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 ter‐
rain features believed to be of importance to the SPLAT!
analysis being
conducted, but noticeably absent from the SDF files be‐
ing used. A
user‐defined terrain file is imported into a SPLAT! anal‐
ysis using the
‐udt switch:
splat ‐t tx_site ‐r rx_site ‐udt udt_file.txt ‐o map.ppm
A user‐defined terrain file has the following appearance
and structure:
40.32180556, 74.1325, 100.0 meters
40.321805, 74.1315, 300.0
40.3218055, 74.1305, 100.0 meters
Terrain height is interpreted as being described in feet
above ground
level unless followed by the word meters, and is added
on top of the
terrain specified in the SDF data for the locations
specified. Be
aware that each user‐defined terrain feature specified
will be inter‐
preted as being 3‐arc seconds in both latitude and longi‐
tude in splat
and 1 arc‐second in latitude and longitude in splat‐
hd. Features
described in the user‐defined terrain file that over‐
lap previously
defined features in the file are ignored by SPLAT! to
avoid ambiguity.GROUND CLUTTER
The height of ground clutter can be specified using the
‐gc switch:
splat ‐t wnjt‐dt ‐r kd2bd ‐gc 30.0 ‐H wnjt‐
dt_path.png
The ‐gc switch as the effect of raising the overall
terrain by the
specified amount in feet (or meters if the ‐metric switch
is invoked),
except over areas at sea‐level and at the transmitting
and receiving
antenna locations.
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 ‐n switch
should be invoked as follows:
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 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:
splat ‐t tx_site ‐R 50.0 ‐s NJ_Cities ‐b NJ_Counties ‐o
topo_map.ppm
where ‐R specifies the minimum radius of the map in miles
(or kilome‐
ters if the ‐metric switch is used). Note that the
tx_site name and
location are not displayed in this example. If display of
this infor‐
mation is desired, simply create a SPLAT! city file
(‐s option) and
append it to the list of command‐line options illustrated
above.
If the ‐o switch and output filename are omitted in these
operations,
topographic output is written to a file named
tx_site.ppm in the cur‐
rent working directory by default.
GEOREFERENCE FILE GENERATION
Topographic, coverage (‐c), and path loss contour (‐L)
maps generated
by SPLAT! may be imported into Xastir (X Amateur Station
Tracking and
Information Reporting) software by generating a georefer‐
ence file using
SPLAT!’s ‐geo switch:
splat ‐t kd2bd ‐R 50.0 ‐s NJ_Cities ‐b NJ_Counties ‐geo ‐o
map.ppm
The georeference file generated will have the same base
name as the ‐o
file specified, but have a .geo extension, and permit
proper interpre‐
tation and display of SPLAT!’s .ppm graphics in Xastir
software.GOOGLE MAP KML FILE GENERATION
Keyhole Markup Language files compatible with Google
Earth may be gen‐
erated by SPLAT! when performing point‐to‐point or re‐
gional coverage
analyses by invoking the ‐kml switch:
splat ‐t wnjt‐dt ‐r kd2bd ‐kml
The KML file generated will have the same filename struc‐
ture as a Path
Analysis Report for the transmitter and receiver site
names given,
except it will carry a .kml extension.
Once loaded into Google Earth (File ‐‐> Open), the KML
file will anno‐
tate 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 dis‐
played as a white
line while the RF line‐of‐sight path will be dis‐
played in green.
Google Earth’s navigation tools allow the user to
"fly" around the
path, identify landmarks, roads, and other featured con‐
tent.
When performing regional coverage analysis, the .kml file
generated by
SPLAT! will permit path loss or signal strength contours
to be layered
on top of Google Earth’s display along with a correspond‐
ing color key
in the upper left‐hand corner. The generated .kml file
will have the
same basename as that of the .ppm file normally generated.
DETERMINATION OF ANTENNA HEIGHT ABOVE AVERAGE TERRAIN
SPLAT! determines antenna height above average terrain
(HAAT) according
to the procedure defined by Federal Communications
Commission Part73.313(d). According to this definition, terrain ele‐
vations along
eight radials between 2 and 10 miles (3 and 16 kilome‐
ters) 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‐3 elevation data, unlike older USGS data,
extends beyond
the borders of the United States. Therefore, HAAT re‐
sults 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 SPLAT! are
SRTM‐derived.
When performing point‐to‐point terrain analysis, SPLAT!
determines the
antenna height above average terrain only if enough to‐
pographic 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 ques‐
tion does not lie within 10 miles of the boundary of
the topography
data in memory.
When performing area prediction analysis, enough topog‐
raphy 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 de‐
grees, 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, SPLAT! reports No Terrain for the
radial paths
affected.
ADDITIONAL INFORMATION
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.
AUTHORS
John A. Magliacane, KD2BD <kd2bd@amsat.org>
Creator, Lead Developer
Doug McDonald <mcdonald@scs.uiuc.edu>
Original Longley‐Rice ITM Model integration
Ron Bentley <ronbentley@embarqmail.com>
Fresnel Zone plotting and clearance determination
KD2BD Software 01 February 2011
SPLAT!(1)
