Locating

From Wiki.GIS.com

Locating is a process used to determine the location of one position relative to other defined positions. Locating is applied for location metering of moving objects and is not to be confused with surveying, which is utilized in reference to stationary terrestrial objects.

Classical passive locating systems operate with a mesh of transmitters and unilateral reception, as GPS, GLONASS, Galileo positioning system and GSM cellnet locating. Further development has led to cooperative systems, where both positions are equipped with respective apparatus and thus provide bilateral measuring.

Metering results are obtained from ranging. The condition for unambiguousness on a line is 2 meterings, in a plane 3 meterings and in a space 4 meterings.

Combining several metering results in a time sequence leads to tracking and tracing.

Contents 1 Locating engine 2 Fuzzy locating 3 Crisp locating 4 Real-time locating 5 Ambiguity with related terms

[edit] Locating engine

A locating engine is a mathematical processing construct that enables the computing of proper coordinates of objects in real time for locating from noised-disturbed and motion-biased sets of longitudinal (distance) data. Coordinates may be either relative or absolute.

[edit] Fuzzy locating

The concept of fuzzy sets applies to wireless locating systems. Hence fuzzy locating describes the attempt to overcome the heavily noise-loaded measurements with locating systems and introducing probabilistics in systems modeling. Common systems design approaches neglect the fact of erratic results and the options to stabilize the obtained coordinates of a location:

• increasing integration time to defuzzify the results
• implying a priori knowledge about physically possible actual locations
• tracking and linear prediction of probable actual locations
• applying an estimating algorithm, for example a Bayesian estimator to determine the actual location under non-linearity conditions.

[edit] Crisp locating

Crisp locating offers precise results for the location of a target, in contrast to fuzzy locating. This quality applies primarily to the metric tolerance of the coordinates. The resulting coordinates describe where a target resides with respect to a defined grid or system of coordinates. The distinction between crisp and fuzzy locating will remain under judgment of the manufacturer or the purchaser respectively.

[edit] Real-time locating

Obtaining locations in real time, i.e. with no delay between appearance in a location and availability of knowledge about the very same location, is Real Time Locating. Real-time locating technically offers, in contrast to systems solutions for navigating and for surveying, a result according to the specified qualities with no hampering time lag between request and response. Especially the locating procedure may not be bound to the dynamics of the bearer or carrier. The distinction between real-time locating and offline locating will remain under judgment of the manufacturer or the purchaser respectively.

[edit] Ambiguity with related terms

Many publications and offers generously mix the terms of locating and positioning. A reason for this ambiguity is originated with the commonly dominant GPS = Global Positioning System with the NAVSTAR satellites. Purpose of this originally military approach was homing of steered rockets and projectiles to targets as well as the main purpose, the navigating of vehicles on ground, at sea and in the air. Common usage of the GPS' systems capabilities leads to continuous imprecise usage of these two terms as well as with other related terms.

For clarification the terms may be segregated semantically as follows (in alphabetical order):

• controlling is steering for following a determined trajectory
• detecting is discovery of the presence of an unknown object in reach
• directing is determining the orientation of an object towards a target
• finding is discovery of a known object at a certain actual location during a search
• fixing is determining a current location with reference to a system of coordinates
• homing is navigating a moving object from remote starting location to target location
• locating is determining a current location of an object by technical means
• mapping is the attempt to refer the current location of a certain object with reference to a map or plan
• navigating is determining the actual and future locations of any moving object from a work position on this object
• orienting is determining the orientation of an object with reference to a system of coordinates
• positioning is determining a new position of an object by moving it to such location
• ranging is determining the distance to an object
• reconnoitering is the task to detect unknown objects in a certain proximity
• scanning is the attempt to detect an object with a sweep over an angle
• sweeping is the covering of a sector to support e.g. detection
• searching is the attempt to locate the whereabouts of a known object upon a triggered start
• steering is determining the heading of a moving object from a control position on this object
• surveying is the mapping of a set of locations according to a given grid