RF Column 33 - July 1994
Copyright (c) 1994,1995 H. Douglas Lung ALL RIGHTS RESERVED

TOPICS:   Low cost computer map databases for RF engineers
              AutoMap
              Street Atlas USA
              MapExpert
              Precision Mapping
          Plotting station coverage maps - tips and tricks

--------------------------------

I'm pleased to report this month that the engineers at Scientific
Atlanta have made some progress with the digital video compression
system we're installing. The annoying software bug that caused the video
to lock up every twelve hours or so is gone, the resolution is improved
to 704 x 480 and it seems to be handling most video without any
noticable compression artifacts. However, I can't give you a report on
how the RF side of the system is doing because we haven't received the
upconverters yet. Our older existing upconverters exhibit a lot of phase
noise which can interfere with the digital data, which is coded as phase
shifts. Hopefully we'll have it on line for testing in June and carrying
programming in July. If the testing goes as planned, I should have some
reports "from the field" in next month's column. I'll be installing and
testing the digital IRD (Integrated Receiver Decoders) using dishes
ranging in size from 3 meters to 9 meters with various LNB's and
different local in terference characteristics.

It seems that during the last month I've been focused on software and
software problems - mostly related to video compression, so somehow it
makes sense to me to do a column this month on software. Not compression
software, but mapping software. Since I use a DOS / Windows based
machine, my report will focus on that platform. I haven't checked,
although I believe some of the programs are also available for the MAC.

I've always enjoyed studying maps. In High School I used US Geological
Survey maps and VFR Sectional charts to find the best sites for ham
radio VHF "mountain-topping". Now I study the charts to locate tower
sites t be discussing them. The programs I'll
describe here are ones I've purchased myself. I couldn't afford to try
all of the ones available! In this survey I'll concentrate on some under
$100 programs and one under $300 program that cover the United States.
Most are available at yo ur local computer store or by mail order.

Many of the map programs you see advertised are either Atlases, nice for
looking at big areas or specialized programs linked to databases for
plotting sales or demographic data. I've found the street atlas type
maps to be the best for locating transmitter sites. It's nice to know
where a site is. It's even better to know how to get there! I've used
two PC maps - AutoMap and AutoMap for Windows and three CD-ROM maps -
Precision Mapping, Street Atlas USA and MapExpert..

My first introduction to computer mapping was a program called
"AutoMap". It's published by AutoMap, Inc., 1309 114th Avenue SE, Suite
110, Bellevue, WA 98004 (Phone 206-455-3552) and can be purchased for
less than $100 from most software distributors. . Figure 1 shows how it
plotted a map of KSTS's transmitter location at 37 degrees, 29 minutes,
5 seconds north latitude and 121 degrees, 51 minutes, 51 seconds west
longitude. You can go to a position on the map by specifying either
coordinates or place name. Don't expect great accuracy, especially in
the DOS version. As you can see from the map, it displayed coordinates
to within a tenth of a minute. It can display a scale of miles and will
read out the coordinates of the cursor. It doesn't default to this mode,
so you'll have to look at the book or menus to find out how to enable it
(look under "Tracking") . Some water features are shown, including coast
lines and rivers. Mountains are indicated by little graphic symbols. A
major 3, 500 foot peak will show up the same as a major 10,000 foot
peak. Elevations for major mountains are available in a text window by
clicking on the symbol. You can use a distance line function to anchor
one end the line on a position and read out the direction (in degrees
true) and distance to the other end as you move the other end around.
This is useful for a quick check of path length and direction.

Figure 1 is taken from the Windows version. While the Windows version
has more features, only the DOS version will plot latitude and longitude
lines. This is important because the map projection AutoMap uses doesn't
aways place true north at the top of the screen. It may be rotated by
ten degrees. Also, only the DOS version allows you to anchor the
distance line at specific points by entering coordinates. In the Windows
version, you have to set it by positioning the mouse, which isn't easy
if you've had a couple cups of coffee. An early version of AutoMap for
Windows 3.0 did not correctly handle locating position by latitude and
longitude. If you have this version, call AutoMap and ask for the fix.
Here's one more problem with AutoMap for Windows. If you mark a location
by coordinates on the map, it will not print those coordinates when you
print the map -- you have to "copy" to the Windows clip board and then
paste it into another program for printing.

In fairness to AutoMap, it was not designed as an engineering tool. It
was designed to show you the major routes from city to city. It does an
excellent job of that given the cost and size of the program. If you
have a fast computer, the Windows version works well. On my 386SX-16 I
usually used the DOS version, simply because the Windows version was too
slow. I'll describe some tips later on for putting a coverage contours
on top of the map. Either AutoMap works well for quick site location,
but they won't help you find the dirt trail to a mountain top site nor
will they show you anything but the major numbered highways. If you
don't have a CD-ROM or tons of disk space, one of these two programs is
probably your best option. For heavy duty site selection, you need a
CD-ROM. (You wanted one anyway, right?)

Street Atlas USA is also geared more to the auto driver than the RF
engineer. It's published on CD-ROM by DeLorme Mapping, Lower Main
Street, P.O. Box 298, Freeport, Maine 04032, telephone 207-865-1234.
Street Atlas USA is widely distributed and usually sells for just under
$100. You will need a CD-ROM drive and Windows to run this program. It
is amazing in its detail. I like the look it -- it offers seamless
coverage of the entire U.S.A. including Alaska and Hawaii on one disk.
Although precise elevation data isn't available, it shows 1000 foot
contour lines and identifies mountain peaks. It includes little dirt
roads and fire trails. Poking around in Volcanoes National Park in
Hawaii, I found it even showed some hiking trails I'd been on! It isn't
perfect -- it misspelled the street I live on in Miami. Overall I was
impressed. Unfortunately, the program as purchased is unsuitable for
locating transmitter sites and difficult to use for plotting coverage
maps! Why? It doesn't include or allow any reference to coordinates by
latitude or longitude! There are ways around this, which I'll cover
later, but they take some time and a database of city coordinates.

Fortunately, DeLorme, the publisher, offers a more expensive version of
Street Atlas USA called "MapExpert". This program does allow positions
to be referenced by coordinates with read out to a thousandth of a
second! It has all the detail of Street Atlas, along with tools that
allow you to draw in features on the map. One hidden feature of the
program is the "point" menu. Displaying that menu you can enter
coordinates whenever you need to position an item on the screen. In
Figure 2 you'll see I've used the point menu to place a strange symbol
at KSTS's precise coordinates. You can enter lines this way too, so it
should be possible to plot coverage maps right in the map program.
Notice the detail in the drawing, the displayed latitude and longitude
lines and the elevation contour lines. The map is plotted to a precise
scale, which makes it easy to use another program to plot coverage maps
to a transparency for overlaying on the map. MapExpert isn't cheap. They
will give you a $100 t rade in for Street Atlas, so you can buy that,
see if you like it, then call DeLorme for the upgrade. MapExpert Version
2.0 was available from DeLorme directly for $295.00 when this Column was
written in June. You must have a CD-ROM drive and Windows is required.
DeLorme uses an automatic detail scaling scheme that makes maps plot
very quickly. This is the program I recommend. It offers the most
features and has the best manual and user interface of any I've tried.

If you don't "do Windows"there is an alternative. Precision Mapping,
published by S&S Publishing, Inc., Post Office Box 552, Lemont, Illinois
60439, telephone 708-257-7616, covers the continental U.S. using two
CD-ROMs. It is widely available for under $100.00 It is the only CD-ROM
I tried that runs under DOS. You'll need 550K of available conventional
memory to run this program -- anything less and it won't start. I found
its interface much more difficult to use than that of the Windows
programs. While it shows a lot of detail, the labels and tools available
make difficult to locate isolated spots without using coordinates
coordinates to find them. You can set the detail level for different
zoom sizes, but it is not easy. The default factory settings don't
always show small roads in less populated areas, even though they are in
the database and will be drawn at greater magnifications. Figure 3 shows
how Precision Mapping displays KSTS's trasmitter site. You'll notice the
road detai l is similar to that of the DeLorme products. (By the way -
the road up to the site is nothing more than a dirt trail and the
eastern side crosses private land and closed to the public.) It doesn't
include elevation contours or show population concentrations.

I mentioned earlier that Precision Mapping came on two disks. One disk
covers areas west of the Mississippi River and the other areas east.
Alaska and Hawaii aren't included. This could be a problem if the area
you're working with spans the river, since there is no overlap between
the two disks. If you have an older computer and don't run Windows,
Precision Mapping is the only choice. It can be configured to work with
EGA, VGA or monochrome monitors. It can even be used without a mouse! My
package included a CD-ROM called "11 Million Businesses' Phone
Directory" covering the U.S. and Canada published by American Business
Information. Overall, inspite of the user interface (which may be
preferred by die-hard DOS users), it is well worth the money if you
don't have the hardware or dollars for MapExpert.

I promised some tips on how to use this mapping software to generate
coverage maps. I won't go into a lot of detail on how to calculate the
coverage contours. This is covered in the FCC Rules and Regulations.
Distance to contours can be found on the applications for broadcast
construction permits or you can calculate it by hand or computer. I use
Dataworld's computer services to calculate the distance to contours at
10 degree or finer increments. Their computer has the elevation data for
the country in it and can quickly calculate the Height Above Average
Terrain (HAAT) for each radial and calculate the contour distance from
the FCC's coverage graphs. I take the tabular data from Dataworld, parse
it into a spreadsheet and convert the data to a batch file I can feed
into Generic Cadd. Generic Cadd then plots the contours. I usually use a
scale of 1 meter = 1 kilometer. Knowing the scale is 1:1000 to start, I
can adjust the scale when printing to match the map. For example, if I
was pl otting a map to overlay Figure 2 I would plot it at 1:12.5 to
obtain the same scale. This method works fine if you know the map scale,
the location of the transmitter and the direction to true north.

If you us AutoMap for Windows or Street Atlas, this data won't be
available. Here's how to calculate it. First, locate some small towns
near the edges of the contours. You'll need three if you want to get a
perfect match. Find the coordinates for the center of each town (that's
why I suggested small towns) from either the map program, or a computer
database. There are several versions of this database available. I
haven't looked for one on CompuServe, but Dataworld lets subscribers use
their program at no charge or you can use the Internet to TELNET to the
Geography Server at martini.eecs.umich.edu 3000. Use one of the distance
/ coordinate calculators to find the bearing and distance to each of
these cities from the transmitter site. Again, there are several
available. Look in the Broadcast Professionals Forum (GO BPFORUM) on
CompuServe. When plotting the coverage map, include these cities on the
map as small points. While you have the program running, calculate the
distance between the cities to generate the horizontal and vertical
scale for the map. Don't be surprised if the two are different,
particularly if you are using a printed map. These scales can be used to
adjust the side of the printed coverage contours, if you are using a
transparency.

If you are doing a quick map for coverage comparisions, it isn't aways
necessary to bother with transparencies. I've had good luck importing
the map into Word For Windows, opening Draw, and then importing the
coverage contours (either as a graphic or DXF file) next to the map.
(You don't want to import it OVER the map, otherwise it will be
difficult to adjust the scale.) You may have to adjust the contour
rotation in the Cadd program if true north on the contour plot doesn't
match true north on the map. Usually the map and contours will be
imported as a collection of individual objects. Use the GROUP command to
make the map one object and all the contours another object. Now you can
select the contour object and use the sizing and positioning handles to
make the points you placed on the contour plot line up with their
respective towns on the map. Once this is done you will know you have
the correct scale and the correct orientation, as well as the correct
transmitter site.

A few words of warning... Read the license agreement that came with the
map software before handing one of your maps over to the sales
department for distribution. There was a license agreement that came
with MapExpert that had to be signed and returned before any maps could
be distributed outside the company. Even then, the number of maps
permitted was limited and there were other restrictions. Also, I
recommend you do not use these maps when maps are required in an FCC
application. The FCC Rules state that in some cases only US Geological
Survey maps may be used. In any case, unless the accuracy of the map can
be traced to a government agency it could be a cause for contesting an
application.

That's all the space for this month. Next month I hope to have the first
reports on our digital video compression conversion. I've also been
receiving a lot of interesting info from manufacturers and I'll try to
get some of that in next month. I received the FCC Type Acceptance data
on the LPTV transmitter I referred to last month as well as some
encouraging test data on the broad band transmission line Dielectric has
developed for use with all channel UHF antennas. Look for my report on
these as well as other developments in RF engineering over the next few
months. I welcome your comments. The best way to reach me is
electronically - via CompuServe E-MAIL at user ID 70255,460 or via the
Internet mail to 70255.460@compuserve.com. I currently have three
Internet connections beside CompuServe, however, I'll probably drop one
of them soon. If you need a copy of my Cheap Remote software, the
calorimetric power calculation program or a text copy (specify Word for
Windows, WordPerfect or DOS text) of a previous column send an E-MAIL to
me and I'll E-MAIl the file back to you. If you use Internet, I can code
the binary files with either UUENCODE or MIME for mailing. Specify which
you want. More conventional ways to reach me are via FAX to
305-884-9661, phone call to 305-884-9664 (9:30-10 AM or 6-7 PM eastern
time only, please), or mail to Doug Lung, 2265 Westwood Blvd., Suite
553, Los Angeles, CA 90064.


Copyright (c) 1994,1995 H. Douglas Lung ALL RIGHTS RESERVED