Maidenhead Locator System

The QTH Locator (also: QTH locator, locator ) is the indication of a location based on an aligned to the longitude and latitude geodetic network. The Earth's surface is thus divided into fields that are used as position information. QTH locator systems have been developed by radio amateurs and amateur radio used mainly in the VHF radio traffic for position information.

The abbreviation QTH is free after the Q key QTH - My Location is or QTH? - What is your location? chosen and is used synonymously for location in the operating technique often.

QTH locator systems arose from the need to have simple, mathematically suitable location information available to calculate the direction and distance between the participants of a wireless connection. The distance is required for the evaluation of amateur radio contests and is also of general interest for the participating radio stations.

QRA Locator

The first locator system was developed under the name QRA Locator by Dieter Vollhardt and taken over in 1959 by the IARU Region 1 VHF Working Group as a standard for position information. The original QRA locator consisted of two letters and two digits (example: EM17 ). Starting at 0 ° longitude and 40 ° north latitude, the first letter stated the longitude 2 ° increments, and the second the latitude in 1 ° increments. The digits divided each of these major fields tenfold in length and eight times in width in 80 small fields.

The four -digit format was expanded in 1963 by adding another letter, was divided by each small box again in 9 small fields (example: EN43d ). Position information was so with an accuracy of 4 ' in East-West, and 2' in north-south direction possible. In 1972 the name was changed to QTH - Locator.

The system quickly became popular and there was a desire to use it worldwide. The was opposed, however, that the field names repeated several times, if you expanded the system to the whole surface of the earth. Many proposals in 1980 on the VHF Working Group meeting in Maidenhead (England) essentially viewed the proposal and published by John Morris ( GM4ANB ) the best. The new system was known as the " Maidenhead Locator " and taken over in 1982 by IARU Region 2 and 1983 of IARU Region 3. In 1984, the IARU Region 1 Conference, the official launch date of the new system in their area on 1986 fixed.

Maidenhead Locator

The Maidenhead Locator is similar to its predecessor. The Earth's surface is 18 × 18 = 324 Größtfelder, each Größtfeld in 10 × 10 = 100 grid squares, each large field in 24 × 24 = 576 divided Kleinfelder. The grid squares are congruent with those of the old system. The maximum and mini-pitches are designated by two letters from AA to RR or AA to XX Large fields with two digits from 00 to 99. Counting begins at the South Pole and 180 ° longitude and runs from west to east or south to north. Example: JO62PL. The underlying coordinate system, the World Geodetic System 1984 ( WGS 84) was set in 1999. The Maidenhead Locator allowed as position information with an accuracy of 5 ' long and 2 ' 30 " width. This corresponds in Germany about an accuracy of 6.33 km in length direction and 4.63 km in width direction. With this accuracy, the system has 324 × 100 × 576 = 18.6624 million small fields.

There are proposals to extend this system and to divide the small fields in 100 micro fields. This improves the accuracy to 30 " long and 15 " wide, and 500 meters is improved. Example with micro fields: JO62PL45

Here the possibilities of expansion are unlimited. Rarely do you find the words with nano fields (English nano squares ), each micro- field in 24 × 24 = 576 nano fields is divided. Again, the letters from AA to XX be used to identify again. The specification of nano fields makes sense only if the base data provides an accuracy of at least 20 m, ie, for example, from a GPS receiver come.

Even more accurate subdivisions are possible in principle, but are not used in practice.