Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2001-03-28
2002-08-27
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S215000, C342S357490, C342S359000, C340S500000
Reexamination Certificate
active
06442480
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for acquiring azimuth information by use of GPS (Global Positioning System) satellites and to a device for acquiring azimuth information for implementing the method.
2. Description of the Prior Art
The term “acquiring azimuth information” as used in this specification encompasses both the concept of “azimuth determination,” meaning to associate an azimuth uniquely with a specific direction, and the concept of “azimuth limitation,” meaning to associate a sector-shaped azimuth range defined by a start azimuth, an end azimuth and a direction of rotation with a specific direction.
Azimuth limitation will be explained first. Consider, for instance, the case of using a representation system in which angular distance (number of degrees) increases clockwise from due north defined as 0 degree. In this system, associating an azimuth of 37 degrees with the specific direction in which one sees a mountain would amount to azimuth determination. On the other hand, if one cannot obtain information of this exactness but, based on some type of information, determines the fact that the direction in question certainly falls within a sector defined by clockwise rotation between an azimuth of 35 degrees and an azimuth of 49 degrees, this would amount to azimuth limitation.
Azimuth limitation becomes a truly useful measure when it can be effected much more rapidly than azimuth determination. A system capable of either rapid azimuth limitation or precise azimuth determination, as occasion demands, has still greater utility. This is because azimuth determination can be conducted when priority is on precision and azimuth limitation be conducted when priority is on speed.
That both azimuth determination and azimuth limitation are actually necessary can be seen from the following concrete example.
Consider the case of a visually impaired person walking outdoors or of a forest ranger, surveyor or other such person who has no choice but to walk through a mountainous region in dense fog, a blizzard or other circumstances of substantially zero visibility. Any of these people would have to walk without being able to see their surroundings. Although a forest ranger or surveyor should be prepared to bivouac, either might decide to continue walking despite zero visibility if having good reason to expect a life-threatening drop in temperature after sunset or a threat to life owing to the approach of a blizzard.
Walking in zero-visibility condition (blind walking) is characterized by the following points:
First, even if a numerical azimuth value for reaching the destination can be obtained from the latitude and longitude of the current location ascertained using a mobile satellite positioning device and the known latitude and longitude of the destination, as is often possible, zero-visibility effectively deprives one of the ability to acquire general azimuth information easily by the sense of vision, so that, in the absence of some other azimuth information acquisition means, the obtained value cannot be used for effectively deciding one's course of action. On the other hand, a compass cannot be used for determining such an important matter as the direction to walk during zero-visibility condition because, depending on the location, the direction indicated by a compass may be strongly affected by magnetic disturbance and deviate greatly from the true direction, and, moreover, is incapable of producing an output indicative of the deviation (error span). The method used by land vehicles of calculating travel direction by repositioning after a suitable amount of travel is also of no use because for this method to work the person attempting to decide the right walking direction would have to walk a distance so great as to be excessively burdensome or sometimes dangerous under condition of zero visibility. The mobile satellite positioning device, being unable to provide an azimuth, is functionally deficient as a tool for supporting a person in zero-visibility condition and incapable of vision-dependent general azimuth approximation in making appropriate walking direction decisions. A method for acquiring azimuth information that can compensate for this shortcoming is therefore necessary.
Second, even if a person should be able to decide a specific direction of travel by some method or other, the person will have difficulty maintaining the travel direction accurately in zero-visibility condition. This is because a person generally maintains a straight line of travel using a feedback loop involving fine correction of travel direction based on a direction visually perceived from a ground feature, a heavenly body or the like, but this is impossible in zero-visibility condition. Unless a person makes frequent direction checks, then, just as when walking with eyes closed, he or she will veer off the initially intended course and is liable to stray into a dangerous region such as one where avalanches are common. The required frequency of the checks is very high. A method that requires considerable work to carry out a check would therefore excessively restrict the person's actions and be worthless from the practical viewpoint. A person walking in zero-visibility condition needs a fast method for acquiring azimuth information that can be simply implemented while continuing to walk and is suitable for frequent information acquisition.
Third, to avoid stumbling, a person who cannot rely on vision must constantly check for the presence of obstacles ahead with the hand or a stick or other extension from the hand. An azimuth determination/azimuth limitation device such as mentioned above would therefore not be very useful in a hand-carried configuration. A device to be worn on the body or clothing is therefore appropriate so as not to restrict the ability of the person walking in zero-visibility condition to grope and probe for the presence of obstacles ahead.
In view of the foregoing considerations, a device for acquiring azimuth information requires the following features for supporting blind walking. First, it must have the ability to determine azimuth with a certain degree of accuracy so as to enable a person walking in zero-visibility condition to initially decide the walking direction to the destination upon obtaining the latitude and longitude of the current location and the destination. Second, to enable a person walking in zero-visibility condition to frequently check whether or not his or her direction of travel deviates from the intended direction, it must be capable of rapid and simple measurement and, further include an azimuth limitation function capable of indicating degree of error. Third, since a person walking in zero-visibility condition strongly needs free use of the hands for discerning obstacles ahead and avoiding falls, it is preferably structured to be worn directly on the body or clothing.
An object of the present invention is therefore to provide a method and device for acquiring azimuth information in zero-visibility condition.
Another object of the present invention is to provide a device for acquiring azimuth information that can be readily worn on the body or clothing.
SUMMARY OF THE INVENTION
For achieving these objects, this invention provides a method for acquiring azimuth information comprising:
a step of disposing a pair of planar antennas each having a hemispherical antenna pattern for GPS satellite signals back-to-back, parallel to each other and vertical, whereby each planar antenna forms a sky coverage area of antenna sensitivity that is a sky quarter-sphere in a direction the antenna faces;
a step of causing a pair of GPS receivers, one connected to each antenna, to scan signals transmitted by GPS satellites in the sky hemisphere;
a step of causing the GPS receivers to output respective channel statuses indicating reception of the signal transmitted by each GPS satellite in the sky hemisphere;
a step of causing at least one GPS receiver to output satellite azimuth for each GPS satellite in the s
Communications Research Laboratory, Independent Administrative I
Cuchlinski Jr. William A.
Hernandez Olga
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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