QTH locator
The QTH Locator (also: QTH locator , locator , to GPS devices also like the Maidenhead Locator , or simply Maidenhead called) is the indication of a location based on a the longitude and latitude aligned geodetic network. This divides the earth's surface into fields that are used as position information. QTH-Locator systems were developed by radio amateurs and are used in amateur radio mainly in VHF radio traffic for position information.
The abbreviation QTH is free after the Q key QTH - My location is or QTH? - What's your location? selected and in the operation and maintenance often synonymous location used.
QTH locator systems emerged from the need to have simple, mathematically usable position information available in order to be able to calculate the direction and distance between the participants in a radio link. The distance is required for the evaluation of amateur radio contests and is also of general interest for the radio stations involved .
QRA locator
The first locator system was developed by Dieter Vollhardt under the name QRA-Locator and adopted in 1959 by the IARU Region 1 VHF Working Group as the 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 indicated the geographical longitude in 2 ° steps and the second the geographical latitude in 1 ° steps. The digits divided each of these large fields ten times in length and eight times in width into 80 small fields .
The four-digit information was expanded in 1963 by adding another letter, which divided each small field into 9 small fields (example: EN43d). Position information was possible with an accuracy of 4 'in west-east and 2' in north-south direction. In 1972 the name was changed to QTH-Locator .
The system quickly became popular and a desire arose to use it worldwide. However, this was countered by the fact that the field names were repeated several times if the system was expanded to cover the entire surface of the earth. Of many proposals, at the VHF Working Group meeting in Maidenhead ( England ) in 1980, the proposal by John Morris (GM4ANB) was seen as essentially the best and published. The new system was known as the Maidenhead Locator and was adopted by IARU Region 2 in 1982 and IARU Region 3 in 1983 . In 1984, the IARU Region 1 Conference set the official introduction date of the new system in its area to 1986.
Maidenhead locator
The Maidenhead Locator has a similar structure to its predecessor. The earth's surface is divided into 18 × 18 = 324 largest fields , each largest field into 10 × 10 = 100 large fields and each large field into 24 × 24 = 576 small fields. The large fields are congruent with those of the old system. The large and small fields are each designated with two letters from AA to RR or AA to XX, the large fields with two digits each from 00 to 99. The counting begins at the South Pole and 180 ° longitude and runs from west to east or south to north. Example: JO62PL. The World Geodetic System 1984 (WGS 84) was established in 1999 as the underlying coordinate system . The Maidenhead Locator allows position information with an accuracy of 5 ′ long and 2 ′ 30 ″ wide. In Germany, this corresponds to an accuracy of 6.33 km in the longitudinal direction and 4.63 km in the latitudinal direction. With this accuracy, the system has 324 × 100 × 576 = 18,662,400 small fields.
There are proposals to expand this system and subdivide the small fields into 100 micro fields. This improves the accuracy to 30 ″ length and 15 ″ width, or 500 meters. Example with micro fields : JO62PL45
The possibilities for expansion are unlimited here. The indication with nanofields (English nanosquares ) is rarely found , whereby each microfield is divided into 24 × 24 = 576 nanofields . Again, the letters from AA to XX are used for identification. Specifying nanofields only makes sense if the basic data provide an accuracy of at least 20 m, e.g. B. come from a GPS receiver.
Even more precise subdivisions are possible in principle, but are not used in practice.
See also
Web links
- QTH locator visualization with maps from OpenStreetMap
- C # class for converting geographic coordinates and QTH locator information as well as calculating distance
- C # classes and Visual Studio project for the conversion of geographic coordinates and QTH locator information with high accuracy as well as distance and azimuth calculation
- Distance and direction calculation with old (QRA) / new (QTH) connoisseur or geogr. Coordinates (description with pgm)