4.4 Object Position Finding Methods
77
reference is one of the oldest methods of aerial vehicle positioning. As practice
shows, mean-square error of aerial vehicle position determination at visual orientation comprises 1–3 km at offset 5–15 km from reference points and 0.1–0.3 km during
flying over a reference point. Herewith, the navigation reference points is meant by
natural or artificial well-prominent at common landscape objects (populated point,
river, road, factory chimney-stalk, etc.) with precisely known coordinates or position.
Orientation accuracy of aerial vehicles can be extremely increased through use of
surveillance radars or trackers of other types.
The main disadvantage of orientation as a method of an object positioning is
impossibility in some cases to determine its position in bad meteorological conditions
and on featureless terrain (sea, desert etc.).
Correlation-extreme navigation has a high potential accuracy and characterized by
immunity to jamming and absence of accumulating errors. However, a practical realization of these systems is connected with a necessity to have large amounts of priori
information on used physical fields parameters en route of an objects movement.
Besides, it possesses a low accuracy which is decreased with increasing of altitude and velocity of an object. However, considering a success in development
of correlation-extreme navigation systems we can note that surveillance-matching
method is a prospective one due to absence of accumulating errors.
Positional method is based on position determination of an object via intersection points representing point of two or more position lines (surfaces) intersection
relatively to the known reference points. Position (surface) line is called a geometric
locus of points on surface (in space), corresponding to some single value of navigational parameter. In radar navigation and radar location, the most widespread is for
the following position lines.
Equal space line (ESL). ESL represents a position line all points of which are
equally spaced from some fixed point. ESL represents a circle.
Equal bearing lines (EqBL). EBL represents a position in each point of which a
direction to an object comprises some constant angle. EBL represents a straight line.
Equal differences in distance lines (EDDL) or loran line of position. EDDL represents a position line in each point of which a distance difference to two points of
ground surface is a constant value. EDDL represents a hyperbola.
Equal sum in distance lines (ESDL). ESDL represents a position in each point of
which a sum of distances to two points on ground surface is a constant value. ESDL
represents an ellipse the focuses of which are the points relatively to which a sum of
distances is determined.
Depending on what position lines are used for determination of an object position
there are rho-rho fixing, theta-theta, range-difference (loran), rho-theta and sumrange distinguished methods.
During application of positional method the radio-navigational stations (radio
beacons) located in points with the known coordinates (navigational guide-points
(NGP)) are used as reference points. Radio-navigational stations can be mounted on
moving platforms (e.g., artificial Earth satellites), if its movement law is known or
can be predicted with prescribed accuracy.
77
reference is one of the oldest methods of aerial vehicle positioning. As practice
shows, mean-square error of aerial vehicle position determination at visual orientation comprises 1–3 km at offset 5–15 km from reference points and 0.1–0.3 km during
flying over a reference point. Herewith, the navigation reference points is meant by
natural or artificial well-prominent at common landscape objects (populated point,
river, road, factory chimney-stalk, etc.) with precisely known coordinates or position.
Orientation accuracy of aerial vehicles can be extremely increased through use of
surveillance radars or trackers of other types.
The main disadvantage of orientation as a method of an object positioning is
impossibility in some cases to determine its position in bad meteorological conditions
and on featureless terrain (sea, desert etc.).
Correlation-extreme navigation has a high potential accuracy and characterized by
immunity to jamming and absence of accumulating errors. However, a practical realization of these systems is connected with a necessity to have large amounts of priori
information on used physical fields parameters en route of an objects movement.
Besides, it possesses a low accuracy which is decreased with increasing of altitude and velocity of an object. However, considering a success in development
of correlation-extreme navigation systems we can note that surveillance-matching
method is a prospective one due to absence of accumulating errors.
Positional method is based on position determination of an object via intersection points representing point of two or more position lines (surfaces) intersection
relatively to the known reference points. Position (surface) line is called a geometric
locus of points on surface (in space), corresponding to some single value of navigational parameter. In radar navigation and radar location, the most widespread is for
the following position lines.
Equal space line (ESL). ESL represents a position line all points of which are
equally spaced from some fixed point. ESL represents a circle.
Equal bearing lines (EqBL). EBL represents a position in each point of which a
direction to an object comprises some constant angle. EBL represents a straight line.
Equal differences in distance lines (EDDL) or loran line of position. EDDL represents a position line in each point of which a distance difference to two points of
ground surface is a constant value. EDDL represents a hyperbola.
Equal sum in distance lines (ESDL). ESDL represents a position in each point of
which a sum of distances to two points on ground surface is a constant value. ESDL
represents an ellipse the focuses of which are the points relatively to which a sum of
distances is determined.
Depending on what position lines are used for determination of an object position
there are rho-rho fixing, theta-theta, range-difference (loran), rho-theta and sumrange distinguished methods.
During application of positional method the radio-navigational stations (radio
beacons) located in points with the known coordinates (navigational guide-points
(NGP)) are used as reference points. Radio-navigational stations can be mounted on
moving platforms (e.g., artificial Earth satellites), if its movement law is known or
can be predicted with prescribed accuracy.