+LONGLEY-RICE PATH LOSS ANALYSIS
+ If the -c switch is replaced by a -L switch, a Longley-
+ Rice path loss map for a transmitter site may be gener-
+ ated:
+
+ splat -t 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 (path loss) in areas sur-
+ rounding the transmitter site. A legend at the bottom of
+ the map correlates each color with a specific path loss
+ range in decibels.
+
+ The Longley-Rice analysis range may be modified to a user-
+ specific value 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 Longley-Rice path
+ loss calculations between all four corners of the area
+ prediction map.
+
+ The -db 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, SPLAT!'s path
+ loss plot can be constrained to the region bounded by the
+ 140 dB attenuation contour as follows:
+
+ splat -t wnjt -L 30.0 -s cities.dat -b co34_d00.dat -db
+ 140 -o plot.ppm
+
+
+ANTENNA RADIATION PATTERN PARAMETERS
+ Normalized field voltage patterns for a transmitting
+ antenna's horizontal and vertical planes are imported
+ automatically into SPLAT! 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 transmit-
+ ter and LRP files, but with .az and .el extensions for
+ azimuth and elevation pattern files, respectively. Speci-
+ fications regarding pattern rotation (if any) and
+ mechanical 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 pattern rotation (measured clockwise in degrees
+ from True North) to be applied by SPLAT! to the data con-
+ tained in the .az file. This is followed by azimuth head-
+ ings (0 to 360 degrees) and their associated normalized
+ 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 speci-
+ fies the amount of mechanical 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 data
+ is followed by the azimuthal direction of the tilt, sepa-
+ rated 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. Eleva-
+ tion angles must be specified over a -10.0 to +90.0 degree
+ range. As was the convention with mechanical beamtilt,
+ negative elevation angles are used to represent elevations
+ above the horizon, while positive angles represents eleva-
+ tions 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 down-
+ ward 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, SPLAT! will
+ interpolate the values provided to determine the data at
+ the required resolution, although this may result in a
+ loss in accuracy.
+
+
+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 cov-
+ erage 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 SPLAT! to rapidly produce a
+ revised path loss map.
+
+ For example, a path loss output file 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 maxi-
+ mum path loss of 140 dB using the following syntax:
+
+ splat -t kvea -L 30.0 -R 50.0 -db 140 -plo pathloss.dat
+
+ SPLAT! path loss output files often exceed 100 megabytes
+ in size. They contain information relating to the bound-
+ aries of region they describe followed by latitudes
+ (degrees North), longitudes (degrees West), azimuths, ele-
+ vations (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 SPLAT! path loss output file take on the fol-
+ lowing appearance (pathloss.dat):
+
+ 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
+
+ It is not uncommon for SPLAT! 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 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 trans-
+ mitter and receiver is unobstructed. If the path between
+ the transmitter and receiver is obstructed, then the ele-
+ vation angle to the first obstruction is returned by
+ SPLAT!. 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 SPLAT! path loss files to reflect antenna
+ pattern data, only the last column (path loss) 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 SPLAT!
+ for generating revised coverage maps:
+
+ splat -t kvea -pli pathloss.dat -s city.dat -b county.dat
+ -o map.ppm
+
+ SPLAT! path loss files can also be used for conducting
+ coverage or interference studies outside of SPLAT!.
+
+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 SPLAT! analysis being conducted, but
+ noticeably absent from the SDF files being used. A user-
+ defined terrain file is imported into a SPLAT! analysis
+ 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 interpreted as
+ being 3-arc seconds in both latitude and longitude. Fea-
+ tures described in the user-defined terrain file that
+ overlap previously defined features in the file are
+ ignored by SPLAT!.
+
+SIMPLE TOPOGRAPHIC MAP GENERATION
+ In certain situations it may be desirable to generate a