What is a 16 point compass rose

Part 2 - THE DIVISION SYSTEMS

STRICH (traditional seafaring)

(For the STRICH as an angular unit in the artillery (6400 ') see below)

This term (rhumb in English and French) denotes the tick marks of the circle. If a circle is divided according to the 32 wind directions, each division ("line") comprises an angle of (360/32 =) 11 ° 15 '.
Right picture: Compass rose from the 18th century. in the Museum of the Stock Exchange in Marseille - Click on the image to enlarge

Note: The transition from the division of the line rose to the graduation rose in the German Navy was the cause of heated discussions in the first half of the XX. Century. It was primarily a matter of which subdivision should be highlighted graphically so that the skipper could give the helmsman easy-to-follow steering commands, corresponding to the previously common ones such as "North by North-West". Approx. Middle of the 18th century. the 32 "points" of the classic wind rose were subdivided (four quarters), so that a total of 128 control commands could be given (see Wikipedia Half and quarter points). There was already a clear formulation with the quadrant rose (see below, N46 ° E). Several proposals have been made to combine the two systems. Captain J. Bortfeldt, editor of North German Lloyd. suggested in 1892 to use a new type of graduation rose in order to avoid conversion errors (excerpt from Hansa, p. 205), since the data on the maps and on the compass rose would be expressed in the same unit. A Mr. G. v. In 1901, Hütschler from Bremerhaven proposed a rose called "UNION" with only 320 tick marks. In the same year, the U.S. Hydrographic Office submitted a proposal for a grade rose in the pilot charts for the month of March. Admiralty Councilor Dr. Maurer invented the so-called shear rose in 1912, where 1 shear corresponds to 15 degrees, divided into three 5 ° intervals, each of which was shown in the middle by highlighting two tick marks. The German-Australian Steamship Company preferred a different solution (the so-called Australrose). The question was only decided in 1941 with the introduction of the graduation rose (source: HANSA - Deutsche Nautische Zeitschrift - complete description online at digiview.bgv.de).

DASH plus non-linear values

On some maps from the 16th century. compass roses are shown surrounded by a non-linear scale, e.g. west and east at zero (or two zeros for infinity), north and south at 17½ and in between the values ​​18, 19, 21, 25, 31½, 46 and 88 ( see picture on the right). These are the distances in ancient nautical miles (1 / 20th of a degree of the circumference of the earth or 3 nautical miles or 5.5 km) that the ship must sail to cover a distance of 1 ° geographic latitude. The lowest number (17½) corresponds to a course on the most direct line perpendicular to the equator (N-S) and the highest (88) corresponds to a course at a shallow angle to the equator, i.e. close to the W-E direction. Such roses can be found in Les premières oeuvres de Jacques Devaulx (Le Havre, 1583) the work of a French maritime pilot and cartographer (link to the website of the French Bibliothèque Nationale GALLICA). A facsimile edition was published under the title Nautical Works with Engl. and German comments published.
Right picture: Denis de Rotis, 1674, Carte de l'Atlantique nord, source Gallica


Photo left. J. Eichhorn: Compass rose on a wall in the airport in Macau - To enlarge, click on the pictures

DEGREE

The degree is the most famous angle division of the circle. It was first used by Ptolemy in his astronomy compendium Almagest and corresponds to one 360th of the circumference. This number is derived from observing the apparent movement of the sun on the horizon over the course of an entire year (365.25) and has been known in many civilizations since ancient times.
A special variant that was used for a long time with both large geological compasses and small pocket compasses consisted of dividing the circle into four quadrants of 90 ° each, with the value zero for north and south. The directions were given in small angular sizes from the nearest zero together with the respective cardinal direction.
Example: 190 degrees then means 10 degrees SW.
Right picture: pocket compass, ca.1850 (Click on the image to enlarge it)

GON or grads

This dimension is the transfer of the metric (decimal) system established at the time of the French Revolution to the division of the circle: a right angle hereby measures 100 gons, the circumference is therefore 400 gons. This division is the official unit in France for all geodetic work. You can observe them on many French compasses, but also on the Italian STOPPANI, on Swiss MERIDIAN instruments or on products from Breithaupt or FPM. The gon was the official unit of measurement in the French army from 1921 (Bulletin Officiel of September 11, 1921). In 1899, experiments were planned in France with ships that carried compasses, maps, etc. with metric units (see Revue du Cercle Militaire No. 21, p. 551, of May 27, 1889), but this was immediately blocked, presumably, because the rest of the world only creates and uses nautical charts and compasses and other documents that have the 360 ​​° division.

French Marching Compass Modèle 1922 with 400 graduation

HOURS

Until the middle of the 19th century, French, German and Austrian pit compasses had a scale in 24 or 2 x 12 hours (with cardinal points in Latin, link to illustration), later together with a 360 ° graduation (see BREITHAUPT, ROSPINI, ROST, STUDER).
- Description in French in L'art d'exploiter les mines de charbon de terre, M. MORAND, 1768, as a pdf on the BnF Gallica website, article Platteau (pp. 213-214)
Right picture: Fig. On p. Pl. VI
- A description of even older pit compasses can be read in Boussoles des mines des XVIe et XVIIe siècles (especially the last paragraph on p. 620).
- Explanation: "The hour (lat. Hora) was the unit of the old compass division; it is equal to 15 °, thus equal to the angle around which the earth rotates in one hour. The hour is divided into eighths with subdivisions, so that is obtained by estimating sixteenth-eighth or twelfth-sixteenths. For Markscheiderische measurements the division of the hours has given way to the graduation; on the other hand, in the case of the geognosing compass, the division of two twelve hours is often used Direction of routes to be driven in the mines. "
(Source: Brathuhn, Lehrbuch der Markscheidekunst, 4th edition, Leipzig 1908).

Partial circle of a pit compass (2 x 12 hours), approx. 1750.

(Click on the image to enlarge it)