GB2101342A

GB2101342A - A navigational aid

Info

Publication number: GB2101342A
Application number: GB08127577A
Authority: GB
Inventors: Brian Timothy Rough
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-03-17
Filing date: 1981-08-25
Publication date: 1983-01-12

Abstract

A navigational aid, to obviate the use of parallel rulers when transferring a compass bearing to a Mercator Projection navigation chart, especially in rough weather, comprises a circular disc rotatably mounted at one end of a rule and clampable in an adjusted position corresponding to a compass bearing, relative to a mark I, by a lock- nut. The disc has a square grid marking to enable it to be aligned with the longitude and latitude of the Mercator Projection chart, whilst the set position of the rule allows a bearing direction to be drawn on the chart. <IMAGE>

Description

SPECIFICATION A navigational aid The invention concerns the combination of the functions of a set of parallel rulers and a compass rose on a Mercator Projection Chart.

Drawing facilities and Chart Tables in many small yachts are often too cramped to allow charts to lie flat so that a pair of parallel rulers can easily and comfortably be used to transfer compass bearings from the chart rose to the position in which they are required.

Even if this facility is generous enough so that the above does not apply, rough weather can soon make this procedure difficult to execute accurately without any erroneous movement of the rulers.

The preferred form of the invention will be described in detail, by way of an example, with reference to the drawings accompanying the specification in which Figure 1 is a detailed section, Figure 2 a plan view of the device.

A compass rose and squared grid marked on a circular plastic disc B, is set in a similar sized circular recess cut into a rule A, which has an enlarged centre section C, to stabilise the disc B, and strengthen the rule A.

The disc B has a central recess D, into which a similar sized, threaded, locating and locking 'pen' E, is set amd fixed to disc B, to facilitate locking the disc and rule together.

A spacing marker F, to allow the free movement of the disc B, is set in a recess in rule A.

A marker G, is located under the lock-nut H, to prevent the nut damaging the surface of rule A. In Figure 2, a central mark at I, on rule A, is used to set the required calibration markXbearing on the disc B.

All calibrations and markings are on the lower surface of the ruler A, and disc B, to avoid parallax and subsequent visual error.

Once a compass bearing has been taken with a hand held compass or radio compass, and the variation allowed for, the bearing is transferred to the device by setting the calibrated disc B, to the required angle at the point I, on the rule A, and locking it in with the lock-nut H.

One side of the ruler A is placed on that point on the chart on which the bearing was taken and this point used on a pivot.

The rule is then swung on this pivot point untii the grid lines on the disc B lie parallel to the lines of longitude or latitude on the chart.

Once this is achieved a line can be drawn on the chart, along the rule A, passing through the bearing point and extending past the point upon which the craft lies and from which the bearing was taken.

This procedure is repeated with two more bearing points to form a 'cocked hat' in which the craft lies.

It will be understood that the invention is not restricted to the details of the preferred form described by way of example which can be modified without departure from the invention as defined in the following claim.

Claim

1. Device which comprises a ruler with a compass rose set in it, with a locking nut, so that compass bearings can be set off and drawn on a chart, using the "bearing point" and lines of longitude and latitude, without reference to the charts compass rose, except to establish the degree of variation between True and Magnetic North.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

SPECIFICATION A navigational aid The invention concerns the combination of the functions of a set of parallel rulers and a compass rose on a Mercator Projection Chart.

Drawing facilities and Chart Tables in many small yachts are often too cramped to allow charts to lie flat so that a pair of parallel rulers can easily and comfortably be used to transfer compass bearings from the chart rose to the position in which they are required.

Even if this facility is generous enough so that the above does not apply, rough weather can soon make this procedure difficult to execute accurately without any erroneous movement of the rulers.

The preferred form of the invention will be described in detail, by way of an example, with reference to the drawings accompanying the specification in which Figure 1 is a detailed section, Figure 2 a plan view of the device.

A compass rose and squared grid marked on a circular plastic disc B, is set in a similar sized circular recess cut into a rule A, which has an enlarged centre section C, to stabilise the disc B, and strengthen the rule A.

The disc B has a central recess D, into which a similar sized, threaded, locating and locking 'pen' E, is set amd fixed to disc B, to facilitate locking the disc and rule together.

A spacing marker F, to allow the free movement of the disc B, is set in a recess in rule A.

A marker G, is located under the lock-nut H, to prevent the nut damaging the surface of rule A. In Figure 2, a central mark at I, on rule A, is used to set the required calibration markXbearing on the disc B.

All calibrations and markings are on the lower surface of the ruler A, and disc B, to avoid parallax and subsequent visual error.

Once a compass bearing has been taken with a hand held compass or radio compass, and the variation allowed for, the bearing is transferred to the device by setting the calibrated disc B, to the required angle at the point I, on the rule A, and locking it in with the lock-nut H.

One side of the ruler A is placed on that point on the chart on which the bearing was taken and this point used on a pivot.

The rule is then swung on this pivot point untii the grid lines on the disc B lie parallel to the lines of longitude or latitude on the chart.

Once this is achieved a line can be drawn on the chart, along the rule A, passing through the bearing point and extending past the point upon which the craft lies and from which the bearing was taken.

This procedure is repeated with two more bearing points to form a 'cocked hat' in which the craft lies.

It will be understood that the invention is not restricted to the details of the preferred form described by way of example which can be modified without departure from the invention as defined in the following claim.

Claim

1. Device which comprises a ruler with a compass rose set in it, with a locking nut, so that compass bearings can be set off and drawn on a chart, using the "bearing point" and lines of longitude and latitude, without reference to the charts compass rose, except to establish the degree of variation between True and Magnetic North.