Overlay Mapper Foregrounds
Layer Notes - States and Provinces
The United States of America (USA) is divided into 50 states + the District of Columbia (DC). Canada is divided into 13 provinces. Mexico is divided into 32 states, though not all are shown in the North American Overlay Mapper, which has a southern border of 24 degree North. A full, sortable list of these 96 areas can be seen by clicking 'Tools' > 'Table Viewer', and choosing 'States and Provinces' from the Select List.
The USA states and Canadian provinces use a two-letter code for an abbreviation, though the Northwest Territories can also use the three-letter 'NWT'. Mexican states all use a three-letter code.
The state/province names and abbreviations are used as an exchange in a number of contests, mainly the international events.
The ARRL does not use the states as region-identifiers in its organization due to amateur population density; instead it divides the USA into 15 Divisions and 71 Sections. For more details, see the 'ARRL Section' page here.
The different states and provinces have a background layer as well as a foreground overlay in the North American Overlay Mapper. The background layer consists of colored areas and borders that define each state or province area; the foreground overlay consists of colored borders and text. The reason for this separation is so that the state/province borders and text can be overlayed and compared with other data; i.e. to see where the state/province borders are on the relief map, or to see which sections fall within which state area.
Layer Notes - Area Codes
The foreground overlay 'Area Codes' shows the boundaries which represent the telephone area codes for United States and Canada along with the three-digit numbers that represent each area. They are also known as Numbering Plan Areas (NPA), and are maintained by the North American Numbering Plan Association (NANPA).
Area Code borders are not currently available for Mexico.
Layer Notes - Zip Codes
The foreground overlay 'Zip Codes' shows the boundaries which represent the Three-Digit ZIP Code Areas for United States along with the three-digit numbers that represent each area.
A U.S. Three-Digit ZIP Code Area represents the first three digits of a ZIP Code. The first digit of a five-digit ZIP Code divides the country into 10 large groups of states numbered from 0 in the Northeast to 9 in the far West. Within these areas, each state is divided into an average of 10 smaller geographical areas, identified by the 2nd and 3rd digits. These digits, in conjunction with the first digit, represent a sectional center facility or a mail processing facility area. These areas are serviced by the U.S. Post Office Sectional Center Facility (SCF). This data was sourced from the Census website.
Zip or Postal Code borders are not currently available for Canada or Mexico.
Layer Notes - Radio Amateurs
The 'Hams' foreground overlay is used with only two maps: Overview East and Overview West. It shows a map of points indicating the presence of Radio Amateurs in the USA and Canada.
The US part of the overlay was created with the latest callsign data from the Federal Communications Commission's (FCC) Wireless Telecommunications Bureau's Universal Licensing System (ULS). The Canadian part of the overlay was created with the latest callsign data from the Industry Canada's Call Sign Database, available to download on the RAC website.
Both files were combined with a Zipcode database to provide a latitude/longitude position for each Amateur in the callsign database, the accuracy depending on the zipcode centroid. These were then plotted with specialist GIS software.
Note: For clarity, it was decided to take no account of the numbers of amateurs present in each 5-digit zipcode or postal-code entity. Each dot show a centroid where 1 or more amateurs have registered their addresses.
Layer Notes - Water Features
The 'Water' foreground overlay contains three different features:
River/Lake outlines and infill
Water Feature names
Island names, for maps that include coastline.
The data for this overlay came from a variety of sources; the major one being VMAP0 data.
Layer Notes - Urban Areas
The 'Urban' foreground overlay contains colored areas that show urban occupation. These can be used to gain an idea of the extent of urban sprawl or city boundaries on the landscape. They are best displayed as an overlay under other layers such as road, rail, or city.
The data for this overlay came from a variety of sources; the major one being VMAP0 data.
The 'Major City' foreground overlay shows three types of point feature:
National Capitals, which are indicated by having their name and point colored red.
State/Province Capitals, which are indicated by having their point colored red. Note that not all State/Province Capitals have a population >50,000.
Major Cities, which are classes as cities with a population >50,000. Note that not all maps contain cities of this size, but where there are none, the overlay will indicate this with a text message.
Choice of cities. Although all national and state capital cities are displayed on the maps, the design-brief was to give a good idea of population centers, whilst trying to avoid clutter and over-crowding of the maps. Therefore, certain large cities have been omitted if very close to more major ones in crowded areas.
The data for this overlay came from a variety of sources; the major one being VMAP0 data.
Layer Notes - Minor City
The 'Minor City' foreground overlay shows two types of point feature, each being differentiated by the color of the point and name. The bolder color indicates towns and cities with a population of between 10,000 and 50,000. The weaker color indicates towns and cities with a population of less than 10,000.
Choice of cities. The design-brief for NAOMI was to give a good idea of population centers, whilst trying to avoid clutter and over-crowding of the maps. Therefore, certain towns and cities have been omitted if very close to larger ones in crowded areas.
The data for this overlay came from a variety of sources; the major one being VMAP0 data.
Layer Notes - Roads and Rail
The 'Road' foreground overlay shows the presence and location of major roads throughout North America. In the USA, the roads shown are the 'Interstates' and the 'US Routes', differentiated with orange and blue colors. In Canada and Mexico, no direct equivalent of these exists, so the choice was made to assign the same colors to major and medium priority routes.
The 'Rail' foreground overlay shows the railroad routes from the National Transportation Atlas Database maintained by the Federal Railroad Administration, available from the Bureau of Transportation Statistics (BTS). No attempt has been made to identify any of the routes.
Layer Notes - Amateur Radio Prefixes
Prefixes are shown in a number of ways - the design-brief was to make them as quickly understandable as possible. Prefixes are split into three main groups, which are shown on the map as follows:
One prefix covers the whole country, without any divisions. Typical examples are C6: The Bahamas. The prefix overlay shows the prefix itself, with no other additions.
A country has a number of prefix areas, each of which correspond to individual country-regions. A typical example of this is VE:Canada. The prefix overlay shows the prefix itself, plus the region-borders that correspond to each prefix sub-division.
A country has a number of prefix areas, each of which correspond to regions composed of a number of individual country-regions.. A typical example of this is W:United States of America. The prefix overlay shows the prefix itself, plus a red border that shows how a number of individual country-regions are grouped to form each prefix sub-division. The region-borders themselves have not been included, but can be added by turning on the 'State' foreground or background overlay.
The size of prefixes used throughout the North American Overlay Mapper is based purely on map-room and clarity of information. No other meaning is intended or should be inferred.
Layer Notes - ARRL Sections
The American Radio Relay League (ARRL) divides the USA into 15 Divisions and 71 Sections. A full, sortable list of these can be seen by clicking 'Tools' > 'Table Viewer', and choosing 'ARRL Sections/Divisions' from the Select List.
The Radio Amateurs of Canada (RAC) use the two-letter province code as their section abbreviation, though the Northwest Territories can also use the three-letter 'NWT' abbreviation.
The sections are used as an exchange in a number of contests, including the popular Field Day and Sweepstakes.
Many of the USA sections consist of entire states; some states have more than one section. Each division is headed by a director. Each section is headed by a section manager.
The different sections have a background layer as well as a foreground overlay in the North American Overlay Mapper. The background layer consists of colored areas and borders that define each section area; the foreground overlay consists of colored borders and text. The reason for this separation is so that the section borders and text can be overlayed and compared with other data; i.e. to see where the section borders are on the relief map, or to see which counties fall within which section area.
Layer Notes - IOTA (Island On The Air)
This foreground overlay shows the IOTA reference numbers for islands qualifying in the popular 'Islands On The Air' award-scheme, also used in the annual IOTA competition. Created in 1964 by Geoff Watts, a leading SWL and editor of the famous DX News Sheet (DXNS), it was taken over by the Radio Society of Great Britain (RSGB) in 1985, and is an amateur radio activity program designed to encourage contacts with island Amateur Radio stations world-wide. The ocean's islands have been grouped into some 1200 IOTA groups, full details of which can be found in the highly recommended 'RSGB IOTA Directory', published by and available from the RSGB's main website. A list of all current IOTA island groups, plus the latest IOTA news, can be found at the RSGB's IOTA website. There are also many internet sites which provide additional information, lists, and photos of island expeditions.
The positions of each IOTA label on the NAOMI overlay correspond to the calculated center of each IOTA entity area. IOTA areas are mostly defined as being contained within a rectangular area of specified Latitude and Longitude range. A full sortable/searchable list of all North American IOTA entities has been provided; you can access this by clicking 'Tools' > 'Table Viewer' > 'NA IOTA'. This data has been provided here at no charge for non-commercial home use only, and remains the copyright of the RSGB.
You can jump straight to any North American IOTA number without having to know its position by using the 'Select Map by Name' > 'IOTA Reference Numbers' map-select tool, on the Map Navigation page.
A useful and unique IOTA resource is located at the EI8IC website. This page lets you enter your own 6-digit Grid Locator; the page will then return a list of all IOTA entities sorted by continent with distance and bearing to each from your own QTH.
Layer Notes - Flags
The 'Flags' foreground overlay contain national, state, and province flags, everyone of which has been hand-edited and resized for this application. The aspect ratio of each flag has been adjusted to a constant value for clarity.
Important: As is stated in the NAOMI License, you are not allowed to copy the flags presented here, or use their images in any other application. If you wish to obtain a complete set of flags that may be used commercially or for most other purposes, please visit the EI8IC website, where you can purchase the full set for only 10 US Dollars online with credit-card or PayPal account.
Layer Notes - Grid Locators
The 'Grid Loc' foreground overlay shows the IARU Grid Locator system, used to identify positions by Radio Amateurs on HF and VHF, and in some contests and operating awards. First proposed at a conference in Maidenhead, England in 1980 (and hence sometimes called Maidenhead Locators), grid squares allow three levels of precision (two, four or six character) to define a station's latitude and longitude. The world is divided into a grid of squares that are ten degrees of latitude high by twenty degrees of longitude wide. Each square is identified by a different two-letter code. For example, the District of Columbia is in location 'FM'.
Each of these squares is further divided into 10 on each axis, giving 100 sub-squares, each of which is one degree of latitude high by two degrees of longitude wide. A diagram of this can be seen in Fig. 1. Each of these squares is identified by the two letters of the alphabet (generally shown in capitals), and two numeric characters. For example, Washington,DC is in location FM18.
For higher precision, each grid square may be further divided into 24 on each axis, giving 576 sub-squares, each of which is 2.5 minutes of latitude high by 5 minutes of longitude wide. A diagram of this can be seen in Fig. 2. Each of these sub-squares is identified by the two letters of the alphabet and two numeric characters as before, plus two lower-case alphabetical characters. Using this system, a station's location is thus identified to within better than 5.6 nautical miles anywhere on the surface of the Earth. For example, the center of Washington, at latitude 38.92N and longitude 77.01W, is in location FM18lw.
There are a number of resources to help you find out your own Grid Locator, and some of these are listed below, but the easiest way is to select the correct NAOMI map and move the cursor over your location. The latitude/longitude and your grid-locator will be shown in the Status Bar, at the bottom of your browser. For more information, visit the Status Bar help-page
Layer Notes - Latitude/Longitude Grid
The 'LatLon' foreground overlay allows us to find the location of any point on the currently selected map. The colors chosen were designed to be visible against a range of backgrounds, without obscuring more important detail. Numbers are included to identify the lines. Those identifying lines of Longitude (North-South) are of three digits, whilst those identifying lines of Latitude (East-West) are of two digits.
To further sub-divide the 1degree grid, use one of the two Graticules. For information about their use and capabilities, see the Graticule help page.
For more exact positional information, the latitude/longitude of your current cursor-position is shown in the Status Bar, at the bottom of your browser. For more information, visit the Status Bar help-page. Depending on the map selected, this ranges in accuracy from ±0.005 degree (small scale) to ±0.04 degree (Overview).
A bit of history: Although the first map reference system was a simple rectangular grid, developed by the Chinese, later map-makers realized that they had to take account of the earth as a sphere. The Greeks derived from the Babylonians (present-day Iraq) the idea of dividing a circle into 360 degrees, and the Greek geographer Eratosthenes (c.276-194 B.C.) was the first to calculate the circumference of the earth, and was reported to have made a world map based on the concept of the earth's sphericity. From this, the Greeks went on to develop the system of spherical coordinates still in use today.
The poles at each end of the earth's axis provide the reference points in its rotation in relation to the celestial sphere. Parallel circles around the earth are degrees of Latitude, and express the idea of distance North or South of the Equator. Lines of Longitude running North or South through the poles express East-West distances. One Meridian is chosen as the meridian of origin, known as the Prime Meridian. In 1884, at an international conference in Washington DC, most countries agreed to adopt the Prime Meridian through the Royal Greenwich Observatory in England, and to calculate Longitude to 180 degrees East and West of Greenwich.