Geometrical instruments – Indicator of direction of force traversing natural media – Magnetic field responsive
Patent
1982-09-03
1984-07-31
Stearns, Richard R.
Geometrical instruments
Indicator of direction of force traversing natural media
Magnetic field responsive
33342, G01C 1702
Patent
active
044621647
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an orienteering compass comprising a compass housing with a moveable north indicator and a base plate having a fixed course line.
In order to enable a user of a compass to move in a given direction, the compass direction, conventional orienteering compasses of the aforedescribed kind are equipped with a moveable compass housing. For the purpose of extracting a compass direction, the compass is placed on a map or chart in a manner such that the course line coincides or extends parallel to the direction from a starting point to a target or goal. The compass housing is then rotated so that lines marked on the compass housing coincide with or extend parallel to meridians on the map. In this respect it must be ensured that the north marking on the compass housing is directed towards north on the map. The compass is then removed from the map and rotated so that the north indicator coincides with the north marking on the compass housing. The correct compass direction is indicated by the course line on the base plate, when the compass is held in this position.
The aforedescribed method is relatively complicated and involves a number of error risks. Since the compass is normally read when completely separated from the map, a error in compass-house setting can take a long time to discover. Thus, the original setting is not checked before it becomes obvious that an error has been made, which may be much too late. Further, it is difficult to teach the aforedescribed orienteering method so that a beginner can readily understand the coordination between compass and map. This is particularly true with respect to the transfer of a direction on a map to a corresponding compass direction. Simultaneous reading of the compass and map is made difficult by the fact that the compass and map are held in different hands, which constitutes a further error risk.
The main object of the present invention is to provide an orienteering compass in which the aforementioned disadvantages are eliminated. To this end the compass according to the invention is so constructed that it must always be used in connection with a map, said compass being characterized in that the compass housing is joined to the base plate in a non-rotatable fashion; and in that the base plate with the compass housing is so arranged that it can be pressed against and readily secured to a map with the course line in the desired direction.
According to the invention, the compass and map must be rotated as a unit in order to obtain the desired direction, and when aligning the map image in question is, at the same time, seen in a correctly orientated position. Thus, with each check of the direction there is also automatically obtained information concerning the map image or picture in question, or conversely each time the map image or picture is looked at it is possible, at the same time, by glancing at the north indicator of the compass, to check that the map is held correctly, i.e. orientated in the north-south direction, since it is only in this direction that the map image or picture agrees with reality.
In accordance with a preferred embodiment of the compass according to the invention, the compass housing is arranged with the centre of rotation of the north indicator located on the extended course line, which in the vicinity of the compass can have the form of a line drawn on the bottom of the compass housing or on the base plate. Further, that part of the course line which extends in front of the compass housing preferably coincides with a longitudinally extending edge of the base plate. This edge is suitably chamfered and provided with a distance scale.
To facilitate pressing of the compass against a map, the compass is suitably provided with a thumb-grip comprising an adjustable stirrup-like structure intended for the thumb, said structure preferably having the form of an elastic band preferably a rubber band, arranged on one side of the compass housing. For the purpose of increasing the friction betewen the thumb and the base pla
REFERENCES:
patent: 57970 (1866-09-01), Reid
patent: 3373429 (1968-03-01), Anderson
patent: 4404752 (1983-09-01), Hanna
Norman Erik B.
Yngstrom Sven A.
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