Locating positions on maps

Details Locating positions on maps Locating positions on maps

2001-07-06

2002-12-24

Louis-Jacques, Jacques H. (Department: 3661)

Data processing: vehicles, navigation, and relative location

Navigation

Employing position determining equipment

C201S045000, C201S045000, C345S111000, C340S990000, C340S995190

Reexamination Certificate

active

06498984

ABSTRACT:

This invention relates to the location of positions on maps.
Various systems are on the market for facilitating the location of one's position on a map. One example, called the Silva GPS Compass, marketed by Silva Sweden AB, of Sollentuna, Sweden, is a portable device which includes a global positioning system (“GPS”) receiver and can display the current position of the receiver in terms of longitude and latitude with an accuracy of about 100 m under the current level of “selective availability” applied by the U.S. Department of Defense who operate GPS. When used with a map having longitude and latitude grid lines, one's position on the map can be located. However, there are two main disadvantages with this system. First, many maps (particularly road and street atlases and steeet plans) do not have any longitude and latitude markings whatsoever. Many other maps (for example British Ordnance Survey (“OSGB”) maps), although having longitude and latitude markings around their border and 5 minute graticule markings on the map, do not have any longitude and latitude grid lines drawn across the map. Thus it can be difficult to locate one's position on the map. Second, because longitude and latitude is a global co-ordinate system, much more information is provided by full longitude and latitude co-ordinates than is actually required to locate one's position on a map covering only a minuscule part of the surface area of the planet, and this can lead to confusion. For example, the old UK Patent Office building in Southampton Buildings, off Chancery Lane, London is situated at (51°30′59″N, −0°06′34″E), but it is difficult to locate that position on the relevant map in the OSGB 1:50,000 Landranger Second Series, Sheet 176, which covers latitudes 51°19′N to 51°41′N approximately and longitudes −0°03′E to −0°38′E approximately, but without any longitude and latitude grid lines. Many GPS receivers also produce co-ordinates in various map-grid systems relevant to different countries' mapping systems. The conversion between latitude and longitude and such map-grid systems is made using known and documented algorithms. Throughout this specification, latitude and longitude is therefore used as an example of any wide-area co-ordinate system as hereinafter defined.
A system which deals with some of the above problems is foreshadowed in patent document WO-A-87/07013 and is marketed by Yeoman Marine Limited, of Lymington, Hampshire, United Kingdom, under the name “Navigator's Yeoman”. Also, an accessory is available for the Silva GPS compass, called the “Silva Yeoman Navimap”, which has a similar effect. These systems use (a) a digitising table on which a traditional map can be placed, (b) a cursor which is movable across the map on the table and has indicators to indicate a required direction of movement, (c) a GPS receiver (or an input to receive a signal from a separate GPS receiver) from which one's current position can be determined, and (d) a processor which determines, from the cursor position on the digitising table and the current GPS position, which way the cursor should be moved so that it is over the current position and activates the indicator lights on the cursor accordingly. Whilst this system has the advantages that it can be used with any traditional map to any scale and of any part of the world, and one's current position can be located by following the indicators rather than thinking in terms of latitude and longitude, it does suffer from two disadvantages. First, before it can be used, the map must be manually referenced with respect to the digitising table so that the processor can translate between the latitude and longitude co-ordinates obtained from the GPS receiver and the co-ordinates of the digitiser table. Referencing can be performed by placing the cursor at two (and preferably three) positions on the chart, and at each position instructing the processor with the latitude and longitude co-ordinates of that position. Alternatively, when used for relative, rather than absolute, positioning when one's current position on the map is known, referencing can be carried out by registering the cursor on the current known position on map and then indicating to the apparatus the north direction of the map and its scale. Second, it requires the use of a digitising table which is as large as the map, or at least as large as a folded portion of the map which is to be viewed at one time without re-referencing.
Another apparatus which deals with this problem is described in patent document WO-A-95/22742, in which a paper map is placed behind a transparent liquid crystal display which can cover the whole area of the map. The map has a mark, for example in the form of a bar code, which can be read by the apparatus and used to correlate positions on the map with latitude and longitude positions. The apparatus also includes a GPS receiver, and the current position obtained from the receiver is converted into a map position, which is then indicated on the LCD by a graphic image, such as crosshairs, to show the current position on the map. However, this apparatus suffers from a number of disadvantages. First, a liquid crystal graphic display is required which is as large as the map, which is thus expensive, cumbersome and liable to be damaged. Second, it is necessary for the map to be used opened out, and the apparatus cannot apparently deal with folded maps. Third, the apparatus can apparently be used only with single sheet maps.
One solution to these problems is to “computerise” the map. In the SkyMap system marketed by Skyforce Avionics Limited of Ramsgate, Kent, United Kingdom, which is primarily designed for aircraft navigation, a representation of the map is held in computer memory. The current position is determined using a GPS receiver, and a relevant part of the map, together with the current position, is displayed on a liquid crystal graphic display. The disadvantages of this sort of system are that (a) it would be extremely expensive if a large, high-resolution, map and colour display were to be used; and (b) many people prefer to use a traditional map. The SkyMap system also has the ability to display the full OSGB grid co-ordinates of the current position so that the position can be located on an OSGB map. However, OSGB maps are not indexed according to the grid reference covered, only according to sheet numbers, and the sheet numbers depend on the scale and series of the maps. Therefore it is not straightforward to select the appropriate map. Also, for a resolution of 100 m, the full eight digit (or two letter and six digit) OSGB grid reference is not needed and not normally used when referring to a particular 1:50,000 sheet, and therefore providing all eight digits can lead to unnecessary confusion.
The present invention is concerned with dealing with the problems mentioned above of the known systems.
In this specification, the following terms are intended to have the following meanings: “Traditional map” means a map which is printed on paper, linen, plastics sheet or the like: “Map co-ordinate system” means a system of co-ordinates which are normally used to define a position on a particular map, and differs from a “Wide-area co-ordinate system” which includes the longitude and latitude system for defining positions on the earth's surface, but also includes other co-ordinate systems. For example, when considering a single map in the OSGB 1:50,000 series, for instance Sheet
176
mentioned above, the co-ordinates (
312
,
815
) are co-ordinates according to the map co-ordinate system for that map, and differ not only from the co-ordinates (51.5164°N, −0.1095°E) according to the longitude and latitude co-ordinate system but also from the full OSGB co-ordinates (
5312
,
1815
) or (TQ,
312
,
815
) according to the complete wide-area OSGB coordinate system; and “Wide-area position transmitting system” means a system which transmits signals which can be rece

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