Boots – shoes – and leggings
Patent
1991-04-05
1994-01-11
Chin, Gary
Boots, shoes, and leggings
364449, 342452, 73178R, G06F 1550
Patent
active
052787630
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with facilitating the plotting of points on a map or navigational chart and with taking data off a chart.
Traditionally, positions are plotted on a chart by drawing intersecting positions-lines determined from observations, measurements and/or calculations, and further positions can be plotted using the dead-reckoning or estimated position methods involving calculations of speed, course, set and drift. The further positions and bearings can then be read-off the chart using instruments and the charts scale and compass markings. Such methods are time consuming and laborious, and requires a degree of expertise with navigational drawing instruments such as a parallel-ruler and dividers or other manual mechanical chart plotting and reading aids.
A very expensive partial replacement for the traditional plotting method is provided by a plotting table which receives an input or inputs from one or more external navigation aids and projects a light beam onto or draws a line at the corresponding location on the chart. In addition to being expensive, such equipment takes up a substantial amount of space and is heavy, and is therefore not particularly suited to anything but large ships.
Electronic chart systems are also being developed to assist in navigation. These have the disadvantages of high cost, the requirement of a cathode ray tube as the chart display, a lack of high resolution in the displayed output, and the lack of a permanent paper record of the output.
A basic navigation aid is described in British Patent Application No. GB 2043909A. In that known aid, a digitising table is employed, on which a chart is placed. A cursor cooperating with the table is movable over the chart and provides a signal which is decoded to give the coordinates in latitude and longitude of the cursor position relative to the chart. The actual position in latitude and longitude of the vehicle being navigated is known from a signal provided by a navigation computer. The actual position signal and the cursor position signals are compared, and an indication is provided by means of lamps on the cursor as to the direction (up, down, right or left) in which the cursor should be moved in order that the cursor and actual positions coincide.
Thus, this known arrangement simply provides a position plotting device, and relies on a signal indicating the actual position of the vehicle.
The present invention seeks to provide a navigation aid which includes certain improvements over the basic aid described in GB 2043909A.
In accordance with a first aspect of the present invention, there is provided a navigational aid comprising a charting surface, A Cursor device movable over the surface, means to provide a signal indicative of the current position of the cursor device on the surface, and means to convert the current cursor position signal from being in terms of a coordinate system of the charting surface to a chart-based signal indicative of the current position of the cursor device in terms of a coordinate system of the chart, characterised by means to store the chart-based signal.
This feature thus enables a position to be conveniently entered by placing the cursor device on that position. Once that is done, it opens up the possibilities for a number of useful calculations to be performed.
For example, the aid may include means to calculate from the stored chart-based signal and the current chart-based signal the distance and bearing of the current position from the stored position and/or vice versa, and means to display the distance and bearing. With this feature, given the bearings of one's current position from two landmarks, or one's bearing and distance from a single landmark, it is a simple matter to plot one's current position on the chart.
Additionally, the-store means may be arranged to store a plurality of such chart-based signals. The aid may then further include means to calculate from the current chart-based signal and from a first and second of such stored chart-based signals the distances of the current
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Agnew Hugh J.
Parfitt Gwyn D.
Woolley Roger K.
Chin Gary
Qudos SA
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