GB2344654A - Survey and navigation device - Google Patents

Abstract

A device 15, for angular determination or measurement, employs a cross-arm structure 17, 19, with a sighting arm for alignment with a target 30, either viewed along it, or from one side; the angle of inclination of the arm being determined by either a pendulum or plumb line 24, freely suspended from the arm intersection 25; a scale 22 interposed between the arms 17, 19; a scale reading being taken where the pendulum or plumb line intersects the scale. Alternatively, a plumb weighted scale (28, Fig. 4B), is pivotally mounted at the intersection of the cross-arms (26), with an index upon one cross-arm (17, 19) for scale reading, whereby, if correctly sighted, the scale reading reflects target angle of elevation or inclination. Other embodiments are disclosed.

Description

Survey & Navigation Device This invention is concemed with survey and/or navigation-and is particularly, but not exclusively concerned with angular determination or measurement.

Such angular determination is required for terrestrial measurement of structural features, landscape slope, grade or pitch in surveying-and (orbital) elevation, or azimuth, of celestial bodies in navigation and astronomy.

In practice a broad division arises in angle determination between, on the one hand, relatively close (say, less than a mile and typically less than, say, 100 metres), stationery, or terrestrial (earth-bound), target objects, such as buildings, or immediately surrounding landscape features, and, on the other hand, longer distance (ie global scale), (relatively) movable (ie in orbit), extra terrestrial celestial bodies.

The scale of measurement, and the accuracy required, broadly dictate the measurement methodology and type of instrument deployed.

That said, some, albeit marginal, overlap arises between broad navigational and surveying requirements-thus admitting a duality of roles, for an instrument capable of angular determination and measurement.

Visual or optical wavelength sighting aside, contemporary, radio-based, systems, such as Radar (Radio Direction and Ranging) and GPS (Global Positioning Satellites), represent a convergence of navigation (from position determination to weapons target-sighting) and surveying-allowing accuracies of a metre or less.

Background Art NAVIGATION Early terrestrial and nautical navigation relied simply upon available individual, line-ofsight,'static', reference landmarks, whether on land, or at sea.

A raw judgement of bearing and distance and intersection or triangulation of bearing points allows a primitive position fix.

Absent some reliable, relatively stationary, ground-based reference, attention turned to celestial bodes, visible to the naked eye, in orbit across the sky, at day or night-vis the sun, moon and stars.

The local time, and periodicity of motion, of planetary systems, at least in the solar system, then become considerations in nautical navigation.

The inventor has hypothesized that, as early as Ancient times (circa 1 st Century AD), albeit rudimentary devices for practical angular determination had been contrived.

Subsequently, the Polynesian race-generally accredited with colonization of the Pacific Islands-are believed to have relied upon some non-terrestrial reference measures.

On a technical and scientific front, a major advance in navigation was the introduction, in the 12th Century, of the magnetic compass into Europe, allowing direction to be determined in relation to a magnetic north pole-albeit not distance or specific location.

Moreover, magnetic direction is susceptible to local variation and distortion by proximity of metal, and is indeterminate near the poles themselves.

It was not until the 18th Century, that navigation at sea became more reliable-with the invention of: the chronometer (John Harrison, circa 1759), in keeping accurate time, for longitude determination; the sextant (John Hadley and Thomas Godfrey, circa 1930), allowing angular sighting of celestial bodies; and the production of British Nautical Almanac (1765).

If the time and position, of individual, or (collectively) several, celestial bodies is known, (nautical) almanacs, or sidereal (time) tables, can be used to determine location upon the earth surface-particularly valuable upon the oceans.

SURVEYING Generally, surveying determines and delineates position, extent and form of (proximate, stationary) features on, or beneath, the earth's surface.

Historically, in, say, Egyptian Pyramid construction, some means of continuous terrestrial reference alignment and checking would have been required.

Fragmentary archeological finds have supported the present Applicant's hypothesis that plumb lines and weights were used in early surveying, in order to strike a reference line-from which angular (offset) could be derived by some form of scale.

Diverse surveying instruments have since been devised, for distance, size and inclination measurement, with varying precision.

Thus, a so-called, theodolite is commonly used for direct read-out of (relative) levels, and thus indirect calculation of level change, or inclination, over a given distance or span.

Effectively, a tripod-mounted, gimbal-supported, telescope is sighted upon a remote upright scale, set at a reference position.

Provision is made for orientating the telescope sight horizontally, by reference to a spirit-level bubble adjustment, through a screw vemier.

A gimbal mount allows swivel of the levelled sight to a relative bearing, allowing triangulation from multiple relative sights at different distances and bearings.

This requires a precision engineering instrument-expensive to produce and vulnerable to damage.

Electronic or computerised theodolites, some with laser light ranging, have been devised, for data-logging of multiple co-ordinates and associated elevations, in relation to (common, universally-agreed) map survey datum.

Related, construction industry, local-scale, levelling, grading and sighting reference and mutual alignment devices include : GB2317012-a profile board, constructed from a rigid post and moveable cross piece, used to set levels on construction sites; GB2298275-a level indicator, using a pendulum, with fixed reference to determine horizontal.

GB2292220-a levelling aid, comprising two pivotally connected arms, one arm acting as a plumb bob, employed to determine horizontal, or to set a specific angle.

Simple variants of such devices may also have a utilitarian role as, albeit primitive or crude, educational or teaching aids-in order to demonstrate raw principles, allow participation in practical application of mathematics, and in particular geometry-and in doing so, reinforce appreciation and understanding of underlying theory.

For example, a rudimentary (in) clinometer-to measure inclination, slant or slope-can be assemble from a protractor, with a string and weight attached.

By measuring an observer's distance from a target object, and using the clinometer to calculate the angle from the observer to the top of the object, basic (triangulation) geometry can be used to calculate the object's height.

However, the accuracy, consistency or repeatability and so reliability of such a (handheld) device approach is limite.

The present invention is concerned to afford a device for robust, consistently repeatable, determination of elevation.

An overall (stark) simplicity and ruggedness of construction, stability and a degree of precision are desirable-in a single integrated device, combining functions, or roles, of survey and navigation.

Such a device could be used where resources do not allow sophistication-such as in the third world-and as a back-up, should more complex systems fail.

Statement Of Invention According to one aspect of the invention, a (measurement) device comprises an elongate, unitary, member, [one end] acting as a pointer, for sighting upon a target, by viewing either along its length, from the opposite end, or from alongside, with the other end as a support fulcrum ; a fixed scale, mounted upon the member, a pendulum or weighted plumb line, freely suspended from the member, to intersect the scale, allowing (direct) scale reading, for determining member inclination, and thus target elevation.

According to another aspect of the invention, a (measurement) device comprises a plurality of intersecting arms, disposed in a cross configuration, one arm deployable as sight line, for line-of-sight viewing longitudinally, from one end to another, in alignment with a remote target object; another arm deployable as a fulcrum, to provide stability, and to act as pivot, about which to adjust sight-line orientation, inclination and/or elevation ; a pendulum or weighted plumb line, freely suspended from the arm intersection; and a scale, interposed between the arms, below the suspended pendulum, or plumb line, to allow a direct scale reading, for determining sight-line inclination, or elevation, of a target object.

Generally, the overall (degree o accuracy, or angular resolution, is determined by the relative scale, or absolute physical size, of the device-a larger scale enabling a more precise determination.

For example, a linear scale rule, of some 90 centimetres in length, allows accuracy to individual minutes of arc-when deployed to bridge the cross-arms of a device according to the present invention.

A one centimetre sub-division of such a scale is equivalent to one degree of arc, in angular determination-and which, in longitude, subtends some 60 nautical miles at the earth's surface.

Thus, 1 millimetre is equivalent to 1 minute of arc-which in longitude represents some 6 nautical miles.

However, if the device is too large, it risks becoming cumbersome and unwieldy.

A comprise, between accuracy from scale size, and accuracy through ability to operate, must be struck.

Embodiments There now follows a description of some particular embodiments of a'dual-role'-ie navigation and/or survey-instrument, for angular determination, according to the invention, by way of example, with reference to the accompanying diagrammatic and schematic drawings, in which: Figures 1A and 1 B show a (measuring) device, comprising a unitary sighting and support member, with'fixed' [arcuate] scale and freely suspended pendulum or weighted plumb line.

Thus, more specifically : Figure 1A shows a unitary member, disposed generally upright, or inclined to the vertical, with a suspended pendulum, or weighted plumb line, at some 90 degrees inclination (ie to the horizontal), as recorded upon scale subdivision markings.

Figure 1 B shows the member pivoted about a lower end fulcrum, such that the distal, pointer end is aligned with a target [object].

The pendulum or plumb line intersects the arcuate scale, allowing direct reading of the inclination of the member-and which, if sighted correctly, allows the angle of elevation of the target to be derived.

Figures 2A and 2B show a (measuring) device, comprising a unitary sighting and support member, carrying a pivoted, freely-rotatable, offset bias-weighted arcuate scale-with an index on the member for taking scale readings.

Thus, more specifically : Figure 2A shows the member disposed generally vertically, or upright, with the index, indicating 90 degrees inclination, on the rotatable scale.

Figure 2B shows the member pivoted about a lower end fulcrum, such that the upper, distal, pointer end aligns with a target [object].

The member index, points to the angle of inclination on the arcuate scale-which, if sighted correctly, allows the angle of elevation of the target to be determined.

Figures 3A and 3B show a multiple (in this case dual) element (measuring) device, of general, differential-length, cross-arm configuration, with a fixed arcuate scale interposed between the arms, and a pendulum, or weighted plumb line, freely suspended from the cross-arm intersection.

Once assembled and erected (in the case of a collapsible structure), the cross-arms are set in a fixed relative disposition (in this case mutually orthogonal)-as a cooperative pair.

One (conveniently a generally longer) arm used for overall support and stability.

The other (relatively shorter) arm deployed to'sight'-by longitudinal axial alignment with-a target.

The overall arm sizes and relative proportions are set to facilitate ease of handling and steady sighting, so that a stable scale reading can be taken.

Thus, more specifically : Figure 3A shows a dual cross-arm (measuring) device, disposed with a support arm initially stood generally upright, or vertical, upon a support surface (ie the ground)and a suspended pendulum, or weighted plumb line, intersecting the arcuate scale, calibrated to give a reading of some 90 degrees.

Figure 3B shows the support arm (progressively) pivoted about a lower end fulcrum, so that the sighting arm-set transversely (in fact orthogonally) thereto-aligns with a target [object].

Sighting-from initial approximation to a final determination-is facilitated and steady or stabilise by the co-operatively disposed support arm.

The pendulum, or plumb line, intersects the arcuate scale, allowing a reading to be taken, of the inclination of the sighting arm-and which, if correctly aligned, is equivalent to target angular elevation.

Figures 4A and 4B show a dual, differential-length cross-arm (measuring) device, with a freely-rotatable, bias-weighted arcuate scale, pivotally mounted at the cross-arm intersection.

An index (eg mark, pointer or graticule) on the support arm, allows scale readings to be taken, for a given relative disposition of the sighting arm.

Thus, more specifically : Figure 4A shows a dual cross-arm (measuring) device, initially disposed with a support arm stood generally upright or vertical, upon a support surface (ie the ground)-and so with a support arm index, indicating some 90 degrees on the rotatable scale.

Figure 4B shows the dual cross-arm device, pivoted about a fulcrum, at the lower end of the support arm, so that the sighting arm axis aligns with a target.

The support arm index, indicates, on the scale, the angle of inclination of the sighting arm.

If correctly aligned, this is equivalent to the target angular elevation.

Figures 5A and 5B show a (measuring) device, of dual cross-arm configuration, as in Figures 3A and 3B, with a fixed arcuate scale and freely suspended pendulum, or weighted plumb line, and in which the upper end of the longer support/sight arm is used to sight the target object.

Thus, more specifically: Figure 5A shows a rigid dual cross-arm (measuring) device, disposed initially with the (longer) support/sighting arm generally upright or vertical, and with a pendulum, or weighted plumb line, intersecting the arcuate scale at some 90 degrees.

Figure 5B shows the dual cross-arm device, pivoted about a fulcrum, at the lower end of the support arm, so that the upper, pointer, end of the (role-reversed) support or sighting arm aligns with a target object.

In this instance, the (transverse) former sighting arm, acts as a scale support.

The pendulum, or weighted plumb line, intersects the arcuate scale, allowing a reading to be taken, of support arm inclination.

If correctly aligned, this allows determination of target angular elevation-through the overall device and sightline geometry.

Figures 6A and 6B show an alternative (survey) use for a dual cross-arm (measuring) device-such as in Figure 3A and 5A-for determining angle of inclination, slope, gradient, fall or pitch, of either remote or adjacent target object, such as a building structure or (hard) landscape feature.

Thus, more specifically: Figure 6A shows a rigid dual cross-arm (measuring) device, pivoted about a fulcrum at the lower end of the'support'arm, so as to align the'support'arm with the slope of a remote (albeit'near distance') target object.

That is, the support arm can also be used for sighting.

Figure 6B shows a rigid, cross-arm (measuring) device, pivoted about a fulcrum, at 'support'arm lower end, so that the (transverse)'sighting'arm is aligned, parallel with the slope of the remote object.

The pendulum, or weighted plumb line, intersects the fixed (arcuate) scale, at an angle, which if correctly aligned, allows target angular inclination, pitch or slope to be determined.

Figures 7A through 7C show alternative variant configurations for the sighting arm.

Thus, more specifically: Figure 7A shows a sighting arm, with cross-sectional profile incorporating an (upper) surface'V'-section groove or trough as the sight-line.

Figure 7B shows a sighting arm, surmounted by cross-hair aiming sights at each end of the sight-line.

Figure 7C shows a hollow sighting arm, with cross-hair sights at each end.

Figures 8A through 8C show alternative scale configurations for use with the (measuring) device described previously.

Thus, more specifically: Figure 8A shows a linear scale, with parallel, linear graduations.

Figure 8B shows a linear scale, with (radially) angled graduations.

Figure 8C shows an arcuate quadrant scale.

Figure 9A and 9B depict variants of the (measuring) device of Figure 3A-the larger the scale, generally the more accurate the angle determination.

Thus, more specifically: Figure 9A shows a hand-held version of the cross-arm (measuring) device, as in Figure 3A.

Figure 9B shows a larger version of the dual cross-arm device, of Figure 3A, stabilised and braced by a support tripod-with a locking swivel mount.

The device is configured to be the size of a person, accommodating a scale of some 90 cm in length.

This in turn allows an accuracy to some one minute of a degree-being equivalent, in navigational terms, to 6 nautical miles of longitude.

Figure 10A and 10B show how a dual cross-arm (measuring) device can be deployed in navigation-to determine latitude, by determining position in relation to the north pole star.

Thus, more specifically; Figure 10A shows how to locate the north pole star, currently Polars, in the sky, by first locating the so-called Plough or Big Dipper constellation.

Figure 10B shows a dual cross-arm (measuring) device sighted on the north pole star, allowing latitude to be determined.

Figures 11 A and 11 B show a dual cross-arm (measuring) device deployed in navigation-to calculate latitude or longitude, by determining position in relation to the sun.

Thus, more specifically ; Figure 11 A shows a'viewer'orientating a dual cross-arm (measuring) device, such that no'lateral'shadow arises, and the device sighting line projects the light of the sun to the centre of the cast shadow.

If correctly aligned, the angle of inclination of the sighting arm, allows the elevation of the sun to be determined.

Figure 11 B shows the dual cross-arm (measuring) device orientated so that a'V'sight on the sighting arm is in line with its shadow-this being the correct alignment from which to determine sun elevation.

Figures 12A through 12C show a dual cross-arm (measuring) device deployed in navigation-to calculate longitude, by determining position in relation to one or more celestial bodies.

Thus, more specifically ; Figure 12A shows the dual cross-arm (measuring) device, orientated such that one member of the sight arm is sighted on due north (on the north pole star), the opposing end of the sight arm indicates due south.

Figure 12B shows the dual cross-arm (measuring) device, orientated at right angles to north and south-with the cross-arm pointing east to west, sighted on a target celestial body.

Figure 12C shows the'viewers'position, as determined by the reading in Figure 12A, in conjunction with the time and an almanac, transposed onto a map.

A'notional'inscribed circle (about the plumb line), of radius is depicted to represent error factor or accuracy, associated with scale reading resolution-with one degree equivalent to some 60 nautical miles, or one minute to some 6 nautical miles.

A second circle represents a subsequent reading'spread', taken on the same celestial body.

The'notional'circle overlap gives a good indication of a'viewer/observer's'actual or true position.

Figure 13 shows a (measuring) device deployed as an aid to pilotage-to determine distance of a vessel from a target object, such as a light-house or charted mountain.

Figures 14A and 14B show the (measuring) device deployed to determine the pitch of a roof or canopy structure-as a building surveying example.

Thus, more specifically : Figure 14A shows a longer support arm, of a dual cross-arm (measuring) device, disposed parallel with the roof pitch of a remote (albeit'near-distance') building.

Figure 14B shows a shorter (transverse) sighting arm, of a dual cross-arm (measuring) device, disposed parallel with the roof pitch of a remote building.

A pendulum, or weighted plumb line, intersects the fixed (arcuate) scale, at an angle, which (if correctly aligned), allows target angular inclination or slope to be determined.

Figure 15 shows the (measuring) device deployed to set levels, say on a construction site, or (hard) landscape contour survey.

Figure 16A through 16C show a collapsible, differential-length, dual cross-arm (measuring) device-foldable into a somewhat more compact linear structure, for carriage and storage.

Thus, more specifically: Figure 16A shows an erect, functional rigid dual cross-arm (measuring) device, with fixed (linear) scale and freely suspended pendulum, or weighted plumb line.

Figure 16B shows the (linear) scale, pivoted about its point of contact with the support arm, to lie over the support arm.

Figure 16C shows the (transverse) sighting arm pivoted about its intersection with supporting arm, to lie behind the supporting to form a linear structure.

Figure 17A through 17E shows a collapsible cross-arm (measuring) device, as in Figures 16A through 16C, with telescopic arms.

Thus, more specifically: Figure 17A shows an erect, rigid dual cross-arm (measuring) device, with telescopic arms, a fixed (linear) scale and freely suspended pendulum or weighted plumb line.

Figure 17B shows the scale pivoted, about its point of contact with the support arm, to lie over the support arm.

Figure 17C shows retraction of the telescopic support arm.

Figure 17D shows pivoting of the (transverse) sighting arm, about its intersection with the support arm, to lie behind the support arm.

Figure 17E shows retraction of the telescopic sighting arm, to produce a compact linear structure.

Figure 18A through 18C shows a (measuring) device with continuous circular (360 degree) scale.

Thus, more specifically : Figure 18A shows a (measuring) device comprising a unitary sighting and support member, with a pivoted, freely-rotatable, bias-weighted circular scale, and an index on the member for scale reading.

Figure 18B shows the unitary member aligned with the target object.

The member index indicates angle of inclination of the sighting member-and which, if correctly aligned, allows target angular inclination to be determined.

Figure 18C shows a dual cross-arm (measuring) device with weighted circular scale, and an index on a support arm, to indicate device inclination.

Sighting cross-hairs, grids or graticules are located on the sighting arm.

Figures 19A and 19B show a circular (measuring) device, with integrated internal support and sighting.

Thus, a circular weighted scale is enclose in a shallow-depth, cylindrical diskhousing.

A viewing window, with index mark, allows scale reading.

Diametrically-opposed graticules are pivotally mounted in the housing and can be deployed as upstands from the surface, for target sighting, or folded way for transport and storage.

In an altemative embodiment (not shown) the casing and intemal wheel or drum may of sufficient depth to allow the sights to be incorporated within the rim-so that a 'viewer'would effectively look'through'the device, in order to sight a target.

A trigger release allows movement of the scale, upon sighting of the target, and positive damping or braking of the scale, in order to steady and lock the readingwhereupon the same reading can be viewed with the device no longer sighted on the target.

The scale would be released when ready for the next sighting.

The same, or a separate trigger release, could be used to deploy or retract the sighting upstands. Thus, more specifically ; Figure 19A shows the circular (measuring device) in a compact configuration, before use.

Figure 19B shows the circular (measuring) device, with sighting graticules hinged at 90 degrees to the housing, and sighted on a target.

Referring to the drawings, a (measuring) device 10, is adapted for use as a tool for navigation or surveying, to determine elevation or (in) clination.

The device 10 comprises a rigid, elongate member 11, the distal end employed as a pointer 12, to sight a target object 30, and the proximal end 14, serving as fulcrum about which member 11 can pivot.

Operationally, rather than haphazard ad hoc sighting, some procedural framework for sighting is helpful for consistent readings.

Thus, for example, the device is conveniently initially stood generally upright, or vertical, and progressively leaned or inclined towards the target.

A scale 22,28 is mounted upon the member 11 intermediate the distal pointer and fulcrum ends.

In order to sight the target 30, a'viewer' (not depicted) stands alongside the device 10, facing the scale 22,28, and pivots the device 10 laterally, until the pointer end 12, of the rigid member 11, aligns with the target 30.

In order to determine the degree of inclination of the device 10, and hence the inclination or elevation of a target 30, the device must incorporate a scale.

The scale can be variously configured, including: an (arcuate or linear) scale 22, secured to member 11, with a pendulum or weighted plumb line 24, freely suspended from member 11 above the scale 22, for reading at the scale intersection; or * a weighted arcuate scale 28, pivotally connected 26, to member 11, with an index 29, for reading on scale 28.

Both the pendulum/weighted plumb line 24 and weighted scale 28 continuously selfalign, under the influence of gravit, to point towards the centre of the earth.

Thus, the degree of inclination of the vertical member 11, is determined by noting the intersection of the scale 22,28, by the pendulum/plumb 24, or index 29, respectively.

Providing the target object 30 is correctly sighted, its inclination or elevation can be determined from the degree of inclination of the unitary member 11.

In an alternative configuration, depicted in Figures 3A through 6B, a (measuring) device is configured as a (dual) cross-arm structure 15-specifically, a [upright] support arm 19, and a [transverse] sighting arm 17.

The cross-arm structure 15 also incorporates a scale, configured as either: a'fixed'scale 22, interposed between cross-arms 17,19-with a free swinging pendulum, or weighted plumb line 24, pivotally attached at the cross-arm intersection 25, for reading at the scale intersection. a bias-weighted and freely-rotatable scale 28, pivotally attached to the cross structure 15, at the cross am 17,19 intersection 25-with an index 29 on the cross member 19, for scale reading.

The cross-arm structure 15, can be employed in various ways to determine elevation or inclination.

For example, a sighting arm 17, may act as the'line of sight'34, for viewing a target object 30.

A'vieweK (depicted in Figures 9A through 9B) would stand in line with the sighting arm 17, at a view point 32, and pivot the support arm 19, backwards and forwards, about its fulcrum 14, until the sighting arm 17 (longitudinal axis) and target object 30 are aligned.

Sighting errors could arise by relying solely upon one distal end of the sighting arm.

Rather, its longitudinal span must be viewed-either from one end to another, or by standing alongside and extrapolating the longitudinal axis to the target.

Target 30 sighting can be facilitated by incorporating a continuous groove 42 in the upper surface of the sighting arm 17, or by mounting sighting cross-hairs or graticules 43, upstanding at opposite ends thereof.

Alternatively, a hollow sighting arm 45 allows sighting by viewing intemally along the (entire) tube length, from one end to another.

Inclination of the sighting arm 17, once aligned with a target 30, is determined by taking a reading from the scale 22,28-so that, if correctly sighted, target 30 angular elevation can be determined.

If more convenient for a given viewing situation and target, the respective roles of otherwise'dedicated'sighting and support arms 17,19 could be reversed or interchanged.

That is, the distal end of the support arm 19 could itself be sighted upon the target 30.

A'viewer', positioned alongside, would then pivot the entire device 15, about the fulcrum

With a correct sighting, target 30 inclination or elevation can be determined.

The device 15 is aiso applicable to surveying-say, to sight a target 30 such as a [distant] roof pitch, gradient or slope, with one of the cross-arms 17,19, set parallel with the target slope line.

To achieve this, a'viewer'could stand alongside the device 15, facing the scale 22, 28, and pivot the device about fulcrum 14, until either arm 17,19, is sighted parallel to the target object.

A reading can then be taken from the scale 22,28.

Given correct sighting alignment, target 30 inclination can be determined.

Another practical application of the measuring device 10 or 15, is as a simple and reliable navigational aid.

More specifically, location can be derived by using the device to determine elevation of celestial bodies.

For example, latitude can be determined by calculating the angle between a position on the earth's surface and the north pole star.

In order to locate the north pole star, currently Polais, the constellation known as The Plough or The Bigger Dipper must first be located.

The Plough constantly revolves around Polaris in an anti-clockwise direction, when viewed in northern latitudes.

At the outer edge of The Plough are two stars known as'pointer stars'.

By following the line of the pointer stars, the next star seen is Polaris-the north pole star (depicted in Figure 10A).

By sighting one arm at the pole star, and reading'indicated degrees'from the scale, latitude can be determined directly.

For an observer taking a sighting, and making an attendant angular elevation determination, from the standpoint of the earth'surface or circumference-rather than a geometric centre of the earth-the great distance of the star-even in relation to the earth's radius-effectively makes any parallax viewing error (s) insignificant.

The cross instrument configuration, and opposed scale mounting, allow measurement of the opposite angle to the actual angle between the star and earth.

The smaller resulting angle is equivalent to some 90 degrees of latitude from equator to pole.

Having determined true north, by sighting the pole star (in the northern hemisphere), true south may also be determined, in that the opposed end of the sight arm will point exactly true south.

In addition to sighting the pole star, navigation can be aided by sighting other celestial bodies, for example to determine longitude.

When viewed from the standpoint of an observer at the earth's surface, celestial bodies, travel or pass from east to west (until lost or eclipsed by the viewing horizon)on a so-called'ecliptic'path across the horizon, in an orderly and predictable mannerthereby achieving given perceived'ascension'and'declination'angles, at particular locations and times.

Accurate observation of one, or several of these celestial bodies, in conjunction with an appropriate almanac and accurate time-piece, allows longitude to be determined.

As the earth orbits around the sun, observed stars appear to move westward every night, at the same observation time, by some 0.98 degrees.

That is, their position, over a given point on the earths surface moves west 58.8 nautical miles.

Simultaneously, as the earth progresses in its orbit around the sun, and seasons change due to the earth's'angle of obliquity'to the ecliptic (path or plane), the elevation or azimuth of the stars also changes, in ascension (apparently rising) or declination (apparently falling or descending).

The overall characteristic pattern of progress is such that, midwinter (the Solstice) is the maximum ascension of the star due south in the sky, and midsummer (the Solstice) is the minimum declination.

For example-if a given star is predicted, by an almanac, to be at an angle of 23.8 degrees above the equator, exactly due south at 0 (zero) degrees longitude at 24.00 hours GMT-it is a relatively straightforward exercise to find an observer's position on the earth's surface, to within some 6 to 12 nautical miles, using a (measuring) device according to the invention.

By employing the preferred configuration of dual, differential-length, cross-arm (measuring) device, of certain embodiments of the invention, an observer's viewing location can be determined through the following sequence of steps: latitude is determined by sighting the cross/sighting arm on the (north) pole star; the'viewer-observeK finds tnue south (opposite direction to the pole star); the'viewer-observer'identifies the star, and its'projected'ascension at midnight, and deducts latitude'made good' (ie through a correction factor); the'viewer-observer'then rotates the (measuring) device by some 90 degrees, so that it is at right angles to a north and south axis, and with the sighting cross-arm pointing east to west. the'viewer-observer'now measures the difference in degrees between the observed position of the star, against its predicted position at 0 (zero) degrees longitude. by correcting the difference between the predicted, and the actual, angle of the star, into degrees and minutes, east or west of 0 (zero) degrees reference datum line (or meridian), the'viewer-observers'longitude can be determined. The same rules apply to lunar observation, although the moon is only observable at certain periods of the month.

If a large (measuring) device is employed, with say a 90 centimetre rule, l millimetre is equivalent to 1 minute of arc-which in longitude represents an accuracy to some 6 nautical miles.

However, with a small hand held device, the accuracy will be to one degree, equal to 60 nautical miles.

Error can be reduced by taking further sightings, over a period of time, and transposing the results upon a chart, as circles measuring 6 or 60 miles, as appropriate.

The (segmental) intersection or overlap of such circles gives a better-and overall good-indication of position.

The (measuring) device can also be deployed to take solar sightings.

The elevation of the sun 52, in conjunction with appropriate almanacs and an accurate time-piece, allows both latitude and longitude to be determined.

Since it is not possible to view the sun directly with the device, an indirect measurement is taken.

For example, a dual, differential-length, cross-arm (measuring) device 15 is orientated such that its shadow 37 is cast on the ground or a horizontal surface.

When no lateral shadows of the device arms 17,19 are visible, and the V sight 42, or sighting tube 45, projects the light of the sun 52 to the centre of the shadow 37, the device is correctly orientated and the inclination of the sight arm 17 can be read from the scale, allowing the elevation of the sun 52 to be determined.

The (measuring) device 10,15 may also be used in pilotage, to determine the distance of a vessel 51 from a known target object 30, such as a lighthouse or a charted mountain-the height of which is known.

By sighting an arm of a (measuring) device 10,15, on the target object 30, its elevation can be determined.

Using basic (triangulation) geometry, the elevation and height of an object can be used to calculate the distance to the object.

To avoid error, account must be taken of height above sea level and distance to the horizon.

Whether configured as a unitary member 10, or a dual cross-arm structure 15, the (measuring) device, must be robust and durable.

As such, construction from materials such as, wood, synthetic plastics (moulded or extruded), or metal are envisaged.

Component List 10 (measuring) device 11 unitary sighting member 12 (distal) pointer end 14 fulcrum 15 (dual) cross-arm (measuring) device, 17 sighting arm 19 support arm 22 (fixed) scale 24 pendulum/weighted plumb line 25 cross-arm intersection 26 pivot 28 weighted scale 29 index 30 target (object) 32 viewpoint 34 line of sight 35 circular (measuring) device 37 shadow 38 shadow of sighting groove 42 groove/channel 43 sighting graticule 45 hollow (sighting) arm 48 tripod 49 trigger release 51 vessel 52 sun

Claims (14)

1. Claims 1. {unitary member + pendulum/plumb} A (measurement) device (10) comprising an elongate unitary member (11), [one end] acting as a pointer (12), for sighting upon a target (30), by viewing, either along its length, from the opposite end, or from alongside, with the other end as a support fulcrum (14); a fixed scale (22), mounted upon the member, a pendulum or weighted plumb line (24), freely suspended from the member, to intersect the scale, allowing (direct) scale reading, for determining member inclination, and thus target elevation.
2. 2. {cross-arm-pendulum/plumb} A (measurement) device (15), as claimed in Claim 1 with a plurality of intersecting arms (17,19), disposed in a cross configuration, one arm (17) deployable as sight line, for line-of-sight viewing longitudinally, from one end to another, in alignment with a remote target object (30); another arm deployable as a fulcrum (14), to provide stability, and to act as pivot, about which to adjust sight-line orientation, inclination and/or elevation ; a pendulum or weighted plumb line (24), freely suspended from the arm intersection (26); and a scale (22), interposed between the arms (17,19), below the suspended pendulum, or plumb line (24), to allow a direct scale reading, for determining sight-line inclination, or elevation, of a target (30).
3. 3. {Differential arm length} A (measurement) device, as claimed in either of the preceding claims, with differential length arms, respectively or interchangeably, co-operatively deployable for sighting and support.
4. 4. {weighted scale} A (measurement) device, as claimed in any of the preceding claims, with a plumb-weighted scale (28), pivotally attached to either a unitary member (11), or a cross-arm intersection (25); an index mark upon one member or arm, alignable with a scale subdivision, for determining target inclination, or elevation.
5. 5. {arcuate scale} A (measurement) device, as claimed in any of the preceding claims, with an arcuate scale, subdivided for direct reading of target angular elevation, or inclination.
6. 6. {circular scale} A (measurement) device, as claimed in any of the preceding claims, with a generally circular scale, (subtending some 360 degree span), subdivided for direct reading of angular elevation, or inclination.
7. 7. {linear scale} A (measurement) device, as claimed in any of the Claims 1 through 4, with a linear scale, subdivided for direct reading of target angular elevation, or inclination.
8. 8. {adjustable arm length} A measurement device, as claimed in either of the preceding claims, with an ajustable length arm or member.
9. 9. {sight line-groove} A (measurement) device, as claimed in any of the preceding claims, incorporating a continuous groove, along a longitudinal side edge of an arm or member, to facilitate taking a sight line to a target.
10. 10. {sight line-sights} A measurement device, as claimed in any of the preceding claims, with upstanding graticules upon an arm or member, to facilitate taking a sight line.
11. 11. {sight line-hollow} A measurement device, as claimed in any of the preceding claims, with a hollow arm or member, to facilitate taking a sight line.
12. 12. {tripod} A (measurement) device, as claimed in any of the preceding claims, with a mounting stand, such as a tripod.
13. 13. {illustrated embodiments} A (measurement) device, substantially as hereinbefore described, with reference to, and as shown in, the accompanying drawings.
14. 14. {method} A method of determining target inclination/declination, or elevation, comprising the steps of target alignment, by pointing either one end, or the entire length of, one of a pair of intersecting arms, co-operatively and interchangeably disposed, as either pointer or support, in a cross configuration, with one end in ground contact, as a fulcrum, about which the pointer arm is pivoted, for target sighting, suspending a pendulum from the intersection of the pointer and support arms, mounting a scale between those arms, and taking a direct reading of target angular inclination/declination, from the intersection of the pendulum with the scale.