GB2319840A

GB2319840A - Navigational aid

Info

Publication number: GB2319840A
Application number: GB9620616A
Authority: GB
Inventors: Raymond Staines
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-10-03
Filing date: 1996-10-03
Publication date: 1998-06-03
Anticipated expiration: 2016-10-03
Also published as: GB2319840B; GB9620616D0

Abstract

A navigational aid comprising a support 2, 3 a plurality of leaves attached to the support and defining a plurality of pairs of adjacent pages 5. Each pair of adjacent pages defines a surface carrying instruction data 6 and at least one data field 7 defining a respective data location. There is also a data recordal member 9 for selectively overlying at least part of the each pair of adjacent pages and having a substantially transparent portion for selectively overlying the or each data field of each pair of adjacent pages to enable data to be recorded or highlighted on the data recordal member at a location thereof overlying a data field. The data fields include at least one first data field for defining a location to record on the data recordal member measured time and position data of one or more astronomical objects, at least one second data field for defining a location to record on the data recordal member data from a navigational reference manual and/or mathematical tables. The instruction data includes instructions on successive pairs of adjacent pages for carrying out successive steps of an astronomical navigation calculation on the data corresponding to the or each first and second data field to calculate a geographical position.

Description

NAVIGATIONAL AID The present invention relates to navigational aids for determining geographical position, and relates particularly, but not exclusively, to navigational aids for determining the geographical position in the event of failure of other position finding systems.

Until fairly recently, the only method of determining the position of a vessel at sea out of sight of land was two use astronomical navigation. However, recent advances in technology have enabled the position of a vessel to be determined by means of on-board devices operating on a system known as geographical position system (GPS) which calculate the position of the vessel from satellite derived data. GPS can be operated by laymen with no navigational skills, and is now the main navigational system for the majority of off-shore cruising yachts. As a result, it is common place for yachtsman to venture out of sight of land with no working knowledge of astronomical navigation.

Given that the yachtsman with no knowledge of astronomical navigation would be in a very serious situation were GPS to fail, many yachtsman take the precaution of having a second GPS as a backup, sailing in large groups, or having on-board teach yourself books on navigation in an attempt to provide some degree of safety should the main GPS system fail.

Such methods clearly suffer from the disadvantage that they are an inadequate substitute for a knowledge of astronomical navigation.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to the present invention there is provided a navigational aid comprising: a support; a plurality of leaves attached to the support and defining a plurality of pairs of adjacent pages, each said pair of adjacent pages defining a surface carrying instruction data and at least one data field defining a respective data location; and a data recordal member for selectively overlying at least part of the or each pair of adjacent pages and having a substantially transparent portion for selectively overlying the or each data field of each pair of adjacent pages to enable data to be recorded or highlighted on the data recordal member at a location thereof overlying a data field, wherein said data fields include at least one first data field for defining a location to record on the data recordal member measured time and position data of one or more astronomical objects, at least one second data field for defining a location to record on the data recordal member data from a navigational reference manual and/or mathematical tables, and wherein said instruction data includes instructions on successive pairs of adjacent pages for carrying out successive steps of an astronomical navigation calculation on the data corresponding to the or each first and second -data field to calculate a geographical position.

By providing a navigational aid in which instructions are provided for carrying out successive steps of an astronomical navigation calculation on measured time and position data of one or more astronomical objects and data from a navigational reference manual and/or mathematical tables, astronomical navigation calculations can be carried out by persons having no knowledge of astronomical navigation. This therefore has the advantage of making astronomical navigation techniques available to mariners out of sight of land without necessitating the complicated learning techniques of astronomical navigation.

In a preferred embodiment, the astronomical navigation calculation is a sight reduction calculation.

Preferably, the calculation utilises the Havesine formula for computing Zenith distance and utilises ABC tables for computing Azimuth.

In a preferred embodiment, the calculation applies the Greenwich hour angle (GHA) to measured longitude data to derive a local hour angle.

Preferably, said data fields include at least one third data field for defining a location to highlight recorded data on the data recordal member for inputting to a table of increments and corrections in the navigational reference manual.

The data fields may comprise at least one fourth data field for defining a location to record on the data recordal member data relating to GHA and correction for minutes and seconds.

The data fields may comprise at least one fifth data field for defining a location to record on the data recordal member data relating to longitude and GHA.

In a preferred embodiment, the data fields include at least one sixth data field for defining a location to highlight on the data recordal member data for inputting to versine tables in the navigational reference manual.

Preferably, the data fields include at least one seventh data field for defining a location to highlight on the data recordal member recorded data for inputting to log versine tables in the navigational reference manual and/or mathematical tables.

By including the use of logarithmic tables in the astronomical navigation calculation, this provides the advantage of reducing any arithmetic steps to addition and subtraction, thus reducing the likelihood of error.

In a preferred embodiment, -the or each said first and second data fields define locations for recording on the data recordal member one or more of date, time, sextant altitude, index error, height of eye and DR position.

Preferably, the astronomical navigation calculation determines at least one geographical position line.

In a preferred embodiment, the navigational reference manual is the nautical almanac.

Preferably, the astronomical object is the sun.

In a preferred embodiment, each said data field has a different colour from at least the surrounding portion of the associated page.

This has the advantage of increasing visibility of data to be recorded or highlighted on the data recordal member.

The navigational aid preferably further comprises means for recording data on the data recordal member in substantially the same colour as at least the region of each associated page surrounding the or each data field.

This has the advantage of obscuring data on the data recordal member surrounding the data overlying a particular data field, with the effect of therefore increasing visibility of the data overlying the data field.

In a preferred embodiment, multiple data fields on a single page have different colours.

This has the advantage of reducing the likelihood of confusion between different data fields.

As an aid to understanding of the invention, a preferred embodiment thereof will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawing, in which: Figure 1 is a schematic view of the navigational aid embodying the present invention.

Referring to Figure 1, a navigational aid 1 in the form of a book comprises a pair of cover members 2, 3 joined at a spine 4 to which a plurality of pages 5 are bound. The navigational aid 1 when open defines a series of pairs of adjacent pages 5 such that the left hand page 5 of each pair carries instruction data 6, and the right hand page carries one or more data fields 7, the purpose of which will be described in greater detail below.

The pages 5 have a width less than that of the cover members 2, 3 to leave an edge region 8 of one of the cover members 3, to which edge region 8 a flexible transparent member 9 is attached by any suitable means such as a series of staples 10 to enable the transparent member 9 to cover the data fields 7 on the right hand page 5 of each pair of pages 5 at which the navigational aid 1 is opened.

A pen or other similar means (not shown) is provided for manually recording data on the transparent member 9 at predetermined locations overlying selected data fields 7 in a colour, typically red, generally the same as the colour of back ground portions 11 of each page 5. Each of the data fields 7 is in a colour strongly contrasting with the colour of the background 11, and where more than one data field 7 occurs on a single page 5, the data fields 7 have different colours. As will be appreciated by persons skilled in the art, this accentuates the difference between regions of the transparent member 9 in those regions overlying and not overlying data fields 7, while obscuring data recorded on the transparent member 9 in those regions not overlying a data field 7. At the same time, the difference in colour between data fields 7 on a single page 5 reduces the likelihood of confusion between different data fields 7. As a further aid to clarity, data fields 7 are joined to the corresponding instructional text 6 by means of arrows 12.

The function of the navigational aid 1 will now be described.

A navigator, such as a mariner on a vessel out of sight of land, who wishes to determine his geographical position, for instance in the event of failure of an on-board GPS system, firstly determines the necessary data for enabling a sight reduction astronomical calculation to be carried out.

Typically, such data will be date, time, height of eye and DR position, and sextant altitude of an astronomical object such as the sun, and index error of the sextant. The navigational aid 1 is then opened to expose the first pair of adjacent pages 5 and the transparent member 9 then overlies most of the right hand page 5. The data mentioned above is then written on those parts of the transparent member 9 overlying the relevant data fields 7 indicated by instructional text 6.

After data has been recorded on the transparent member 9, the page of the navigational aid 1 is turned to expose the next pair of adjacent pages 5, the right hand page of which is now generally covered by the transparent member 9. In this way, it will be appreciated by persons skilled in the art that data has effectively been transferred from the first pair of adjacent pages 5 to the second pair of adjacent pages 5 in a relatively simple manner. A left hand page 5 subsequent to the first may have instructional text 6 for locating a particular page in the nautical almanac and/or a particular page and area in the relevant mathematical tables. The corresponding data fields 7 highlight data recorded on the transparent member 9 and thus transferred from previous pages 5, and provide locations for recording on the transparent member 9 data from the nautical almanac or mathematical tables.

To facilitate understanding by the user, one or more of the pages 5 may also have an example set of figures already input, thus allowing the user to see how the initial information input is retrieved forms the basis of subsequent calculations and to illustrate where information lies within the nautical almanac and mathematical tables, such as ABC tables and of how a chart is used.

By following the instructions on successive left hand pages 5 a sight reduction calculation is carried out on data recorded on the transparent member 9 to provide a geographical position line. When two position lines are derived, the navigator is able to determine his geographical position.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. In particular, the above embodiment is designed to use the Havesine method of sight reduction, although any other sight reduction method, including sight reduction methods using an electronic calculator, could be used. Similarly, the calculation process may be condensed so as to be completed with a smaller number of pages 5 by having more calculations per page, or may conversely be expanded to cover more pages.

Claims

CLAIMS:

1. A navigational aid comprising: a support; a plurality of leaves attached to the support and defining a plurality of pairs of adjacent pages, each said pair of adjacent pages defining a surface carrying instruction data and at least one data field defining a respective data location; and a data recordal member for selectively overlying at least part of the or each pair of adjacent pages and having a substantially transparent portion for selectively overlying the or each data field of each pair of adjacent pages to enable data to be recorded or highlighted on the data recordal member at a location thereof overlying a data field, wherein said data fields include at least one first data field for defining a location to record on the data recordal member measured time and position data of one or more astronomical objects, at least one second data field for defining a location to record on the data recordal member data from a navigational reference manual and/or mathematical tables, and wherein said instruction data includes instructions on successive pairs of adjacent pages for carrying out successive steps of an astronomical navigation calculation on the data corresponding to the or each first and second data field to calculate a geographical position.

2. A navigational aid according to claim 1, wherein the astronomical navigation calculation is a sight reduction calculation.

3. A navigational aid according to claim 1 or 2, wherein the calculation utilises the Havesine formula for computing Zenith distance and utilises ABC tables for computing Azimuth.

4. A navigational aid according to claim 1 or 2, wherein the calculation applies the Greenwich hour angle (ERA) to measured longitude data to derive a local hour angle.

5. A navigational aid according to any one of the preceding claims, wherein said data fields include at least one third data field for defining a location to highlight recorded data on the data recordal member for inputting to a table of increments and corrections in the navigational reference manual.

6. A navigational aid according to any one of the preceding claims, wherein the data fields comprise at least one fourth data field for defining a location to record on the data recordal member data relating to GMA and correction for minutes and seconds.

7. A navigational aid according to any one of the preceding claims, wherein the data fields comprise at least one fifth data field for defining a location to record on the data recordal member data relating to longitude and GHA.

8. A navigational aid according to any one of the preceding claims, wherein the data fields include at least one sixth data field for defining a location to highlight on the data recordal member data for inputting to versine tables in the navigational reference manual.

9. A navigational aid according to any one of the preceding claims, wherein the data fields include at least one seventh data field for defining a location to highlight on the data recordal member recorded data for inputting to log versine tables in the navigational reference manual and / or mathematical tables.

10. A navigational aid according to any one of the preceding claims, wherein the or each said first and second data fields define locations for recording on the data recordal member one or more of date, time, sextant altitude, index error, height of eye and DR position.

Il. A navigational aid according to any one of the preceding claims, wherein the astronomical navigation calculation determines at least one geographical position line.

12. A navigational aid according to any one of the preceding claims, wherein the navigational reference manual is the nautical almanac.

13. A navigational aid according to any one of the preceding claims, wherein the astronomical object is the sun.

14. A navigational aid according to any one of the preceding claims, wherein each said data field has a different colour from at least the surrounding portion of the associated page.

15. A navigational aid according to any one of the preceding claims, further comprising means for recording data on the data recordal member in substantially the same colour as at least the region of each associated page surrounding the or each data field.

16. A navigational aid according to any one of the preceding claims, wherein multiple data fields on a single page have different colours.