Puget Sound Area FCC Line A Regulations, Interpreted

The FCC Line A Regulations were established during the WARC 79 conference, (World Administrative Radio Conference, 1979) and are meant to protect Canadian Land/Mobile operations near the US/Canadian border from interference. There is a Line B in Canada that mimicks the US Line A, as well as a Line C and D between Alaska and Canada and for the same reason. Originally, the definition of Line A in Section 90.7 is taken from Paragraph 2 of Arrangement A contained in the revised Technical Annex to the agreement between the United States and Canada on the "Coordination and Use of Radio Frequencies Above 30 Megacycles per Second", signed at Ottawa on June 16 and 24, 1965. Due to the lack of easy to interpret information, I was prompted to wonder what and where the Line A Restrictions physically are, how to map the boundaries it defines, and how it affects Amateur 70 cm Operations, and other Radio Service Operations such as GMRS in the Puget Sound Area.

The Challenge that Line A presents in the Puget Sound Region of Northwest Washington State is that once the line leaves it' s path along the 48th Parallel, it becomes difficult to plot along it's diagonal and southwesterly path towards Aberdeen Washington. It leaves those who need to know begging the question of where they physically are in relation to where the line physically is. There is a real and genuine legal need to know.

To begin my search for information, I consulted the ARRL Repeater Directory, inside which I found a graphic, about two inches in size that roughly shows where Line A hits the ground along the northern border of the United States. Although it gives a general description, this graphic is inadequate for use in the Puget Sound Area because it doesn't accurately show Radio Operators where they really are in physical relationship to Line A.

After searching the Internet for more concise information and finding little, I set out to develop a method for creating a detailed map with improved accuracy that would be easy to draw and interpret for anyone needing to know where this line physically is located. Most of the information I needed, in order to develop this, was found in the FCC Part 97. It just needed a little further interpretation.

To Quote the FCC Part 97 Regulations, The Rule for Line A was found in The FCC Part §97.303 Frequency Sharing Requirements: (f) In the 70 cm. band: (1) No amateur station shall transmit from north of Line A in the 420-430 MHz segment.

The Legal Description of Line A was found in FCC Part 97, and is stated as:

§97.3 Definitions. (29) Line A. Begins at Aberdeen, WA, running by great circle arc to the intersection of 48º N, 120º W, thence along parallel 48º N, to the intersection of 95º W, thence by great circle arc through the southernmost point of Duluth, MN, thence by great circle arc to 45º N, 85º W, thence southward along meridian 85º W, to its intersection with parallel 41º N, thence along parallel 41º N, to its intersection with meridian 82º W, thence by great circle arc through the southernmost point of Bangor, ME, thence by great circle arc through the southernmost point of
Searsport, ME, at which point it terminates.

To most people, this looks like the language seen when we read a title company's legal description of our homes. To simplify this, I'll show which part of this regulation affects the Puget Sound Area and how to map this out for ourselves.

To begin, The only part of the definition we need to calculate from is this: Begins at Aberdeen, WA, running by great circle arc to the intersection of 48º N, 120º W. From this point, Line A follows the 48th Parallel east across the Midwest. There are 75 miles between Parallels, and the 49th Parrallel represents the US/Canadian border. Using the FCC Website Definition of Line A,
http://www.fcc.gov/oet/info/maps/canline/linea.html
The FCC officially puts the Latitude and Longitude for Aberdeen Washington at: 46º:58.00N Lat. 123º:50.00W Long. Based on this FCC Coordinate Location for Aberdeen Washington, and the Confluence Location, 48º N Lat, 120º W Long, given by the FCC in the Line A definition, the great circle arc is calculated as an arc line running from southwest at Aberdeen, northeast toward a location mapped as approximately 11 miles north and one mile east of the southern tip of Lake Chelan in Chelan County Washington.

Skipping the spherical trigonometry involved, I located a calculator online that would calculate the great circle arc headings and distances.
http://www.waypoint.org/gps1-calc.html
Using this, I found that: The Arc Line, True North Compass Heading from Aberdeen is 66.8 degrees. The Arc Line, True North Compass Heading from the Lake Chelan Area is 249.6 degrees The distance of the Arc Line is 191.3 statue miles. I tried several javascript based calculators online,and found that results vary but are similar to these results which I have listed here as an example. Authors Note, If someone familiar with the circular triginometry involved would like to tighten up these figures, please feel free to forward this information to the webmaster. After figuring the differences of these headings for a flat map projection, I found that over this short distance, a great circle arc line is virtually straight with only a 2.8 degree bend toward the northwesterly direction. What this means to most of us is that on a flat map of Washington, a straight line drawn between these points is as accurate as we need for a map of this resolution.

The findings, after drawing Line A on a map were enlightening. Since it runs diagonally through the Puget Sound Area, locations south of, yet near to Line A are: Tacoma, Federal Way, Auburn, Kent, Maple Valley and North Bend. North of, yet close to Line A are: Gig Harbor, Des Moines, Sea Tac, Burien, Renton, Snoqualmie, Seattle, and Bellevue. It was a surprise to learn that Wenachee and Leavenworth are both south of Line A, while Skykomish is North. The FCC has provided a web page which uses a beta javascript, where you can provide the coordinates of your location and it will tell you whether you are north or south of Line A
http://wtbwww05.fcc.gov/cgi-bin/scripts/lineac.pl

For those who would like to use their GPS units to help locate the physical location of Line A, some of the more advanced units will allow the projections of waypoints where they are needed without having to physically go to that said location. As of May 2nd, 2000, GPS Selective Availability was removed, resulting in highly increased accuracy from civilian GPS units.
GPS Selective Availability Removal
Projecting and storing these waypoints can either be done in the GPS unit itself, or there is mapping software available from the various GPS manufacturers for use with their respective brands of GPS units. This software can be used in PC computers to accomplish the locating and positioning of these waypoints and then this data can be uploaded to the GPS unit itself. Once both ends of this section of Line A are calculated and made into waypoints, the software can plot where other intermediate, user defined waypoints along Line A can be located for use in the field. If the software is not available, both the Aberdeen and Chelan area waypoints can be put into the GPS manually.
Using the Line A annotated Map, made from following these instructions; a compass corrected for Magnetic Declination, and the GPS unit programmed with at least the two ends of this section of Line A as waypoints; bearings and back bearings between the two main waypoints should be easy to determine in the field, so that intermediate waypoints can be created.

One important point of caution should be considered at this time. GPS units are meant to orient the user in reference to true north as a default setting, though this can be a user definable function in many GPS units. The FCC rule of Line A is referenced to true north, so it will be useful in this instance to determine that the GPS unit is set for this as well. it is just as important to remember that a compass is not referenced to true north. Compass needles always point toward magnetic north, and it is incumbant upon the user of any compass to determine the proper, up to date magnetic declination before using a compass with a map in any area.

Magnetic Declination varies not only with location, it also varies at a particular location over time. In some parts of the U.S. the magnetic declination is changing at a rate of 1 degree in ten years. If an older map, based on the date of the map's publication, is used for this exercise, accuracy can be affected by literally hundreds or thousands of feet due to this change of declination. Please consult the following link for up to date information on how to get the most accurate Magnetic Declination for your area:
Determining Accurate Magnetic Declination

Amateur Radio is a very portable hobby. There are places in the Puget Sound Area where it is legal to utilize and enjoy this grey area spectrum. If you live near this line, and operate between 420-430 MHz, Especially for ATV Repeater or Simplex, Repeater Control Links, or other Experimental Operation. Draw your own map to determine where you operate in relation to it. It is always a good idea to be sure.

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