If the reference direction is north (either true north, magnetic north, or grid north), the bearing is termed an absolute bearing. Measured in this way, a bearing is referred to as an azimuth. In land navigation, a bearing is ordinarily calculated in a clockwise direction starting from a reference direction of 0° and increasing to 359.9 degrees. There are several methods used to measure navigation bearings:ġ. The difference between a magnetic bearing and a compass bearing is the deviation caused to the compass by ferrous metals and local magnetic fields generated by any variety of vehicle or shipboard sources (steel vehicle bodies/frames or vessel hulls, ignition systems, etc.)Ī relative bearing is one in which the reference direction is straight ahead, where the bearing is measured relative to the direction the navigator is facing (on land) or in relation to the vessel's bow (aboard ship). It should be very close to the magnetic bearing. In vehicle or marine navigation, a compass bearing is measured in relation to the magnetic compass of the navigator's vehicle or vessel (if aboard ship). If the two vessels are travelling toward each other and the relative bearing remains the same over time, there is likelihood of collision and action needs to be taken by one or both vessels to prevent this.Ī bearing can be taken to a fixed or moving object in order to target it with gunfire or missiles.Ī bearing can be taken to a person or vessel in distress in order to go to their aid or, when that is not possible, to report the person or vessel to authorities or someone who can go to their aid.Ī true bearing is measured in relation to the fixed horizontal reference plane of true north, that is, using the direction toward the geographic north pole as a reference point.Ī magnetic bearing is measured in relation to magnetic north, that is, using the direction toward the magnetic north pole (in northeastern Canada) as a reference.Ī grid bearing is measured in relation to the fixed horizontal reference plane of grid north, that is, using the direction northwards along the grid lines of the map projection as a reference point. PilotingĪ bearing can be taken on another vessel to aid piloting. These types of bearings are sometimes termed limit bearings, aim-off bearings, danger bearings, or index bearings. Upon reaching the road, the navigator simply turns west to ensure he will reach the destination. Similarly, a land navigator might walk a bearing several degrees to the east of his actual course to avoid difficult ground, or to intercept an intersecting position (such as a road or trail) leading to his/her destination. Or, if moving through a channel with obstructions to the west and which is not well-marked with buoys, it can be decided that the vessel might have to stay to east of a particular charted object. If it does not, an anchor watch must inform someone to take action. For instance, if anchored in a harbor with a shore to the north, it can be decided that the vessel must stay to the south of an object to its east. However, a pre-calculated bearing to a charted object can be also be used as a precautionary measure. This bearing can be used to determine the position of the vessel or landmark when used in conjunction additional bearing(s) or other information (e.g. Use of bearings Determining a positionĪ bearing can be taken relative to a charted or mapped object at a specific time. Under this definition, for example, a given azimuth in degrees would be expressed as 60°, while the equivalent bearing would be expressed as N 60° E. ![]() ![]() In contrast, an azimuth was a clockwise measurement of a circle from a zero point at a fixed horizontal plane of reference (such as a north meridian), expressed in degrees, mils, or other unit of angular measurement. ![]() More specifically, a bearing was measured both east and west from north and south, divided into four quadrants. When approaching the Visual Approach Chart and Aerodrome Landing Chart data sheets are automatically placed on the display, overlapping the background map.In land navigation, a bearing was traditionally defined in land surveying terms as a fixed number line which gave the smallest arc (never to exceed 90 degrees). You can have the Avioportolano chart on the screen at an optimum zoom resolution by choosing the settings and configuration you want. You can choose the whole of Italy or four possible portions: North, North/Centre, South and Islands. The Avioportolano charts are loaded directly from the tablet (APPLE and GOOGLE). "Avioportolano Airfield Manual" composed of more than 1500 documents describing in detail the entire network of Italian airports, airfields and ULM airstrips is also available for download inside the APP. Air Navigation Pro is one of the first air navigation software produced for tablets and smartphones.Avioportolano has been providing the data of Italy and the VFR charts to Air Navigation Pro since 2010.
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