com.bbn.openmap.tools.terrain
Class LOSGenerator

java.lang.Object
  com.bbn.openmap.tools.terrain.LOSGenerator

public class LOSGenerator
extends java.lang.Object

A Class that can do Line-Of-Sight calculations between two points. Uses the DTEDFrameCache to get elevations.

Field Summary

protected int	INVISIBLE
static java.util.logging.Logger	logger
protected int	MAYBEVISIBLE
protected int	VISIBLE

Constructor Summary

LOSGenerator()
Not the preferred way to create one of these.

LOSGenerator(DTEDFrameCache cache)

Method Summary

static double	calculateLOSSlope(int startTotalHeight, int endTotalHeight, double arc_dist) Calculate the slope of a line between two points across a spherical model of the earth.
double	calculateLOSSlope(LatLonPoint startLLP, int startTotalHeight, LatLonPoint endLLP, int endObjHeight) CalculateLOSslope figures out the slope from one point to another.
DTEDFrameCache	getDtedCache()
boolean	isLOS(LatLonPoint startLLP, int startObjHeight, boolean addStartElevation, LatLonPoint endLLP, int endObjHeight, int numPoints) Check to see if two points are within line of sight of each other, taking into account their elevations above Mean Sea Level as retrieved by a DTED database, and any other addition height of each object.
void	setDtedCache(DTEDFrameCache cache)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INVISIBLE

protected int INVISIBLE

VISIBLE

protected int VISIBLE

MAYBEVISIBLE

protected int MAYBEVISIBLE

logger

public static java.util.logging.Logger logger

Constructor Detail

LOSGenerator

public LOSGenerator()

Not the preferred way to create one of these. It's full of defaults.

LOSGenerator

public LOSGenerator(DTEDFrameCache cache)

Method Detail

setDtedCache

public void setDtedCache(DTEDFrameCache cache)

getDtedCache

public DTEDFrameCache getDtedCache()

isLOS

public boolean isLOS(LatLonPoint startLLP,
                     int startObjHeight,
                     boolean addStartElevation,
                     LatLonPoint endLLP,
                     int endObjHeight,
                     int numPoints)

Check to see if two points are within line of sight of each other, taking into account their elevations above Mean Sea Level as retrieved by a DTED database, and any other addition height of each object.

Parameters:

startLLP - location of point 1.

startObjHeight - the elevation of point 1 above the surface, in meters. The surface elevation of the point will be looked up and added to this value.

addStartElevation - true if startObjHeight also needs DTED lookup added to it.

endLLP - location of point 2.

endObjHeight - the elevation of point 2 above the surface, in meters. The surface elevation of the point will be looked up and added to this value.

numPoints - number of sample points to check between the two end points. Can be dependent on the Projection of the current map, and based on the number of pixels between the projected points. Could also be based on the number of elevation posts between the two points in the DTED database.

Returns:

true of their is a line-of-sight path between the two points.

calculateLOSSlope

public double calculateLOSSlope(LatLonPoint startLLP,
                                int startTotalHeight,
                                LatLonPoint endLLP,
                                int endObjHeight)

CalculateLOSslope figures out the slope from one point to another. The arc_dist is in radians, and is the radian arc distance of the point from the center point of the image, on the earth. This slope calculation does take the earth's curvature into account, based on the spherical model. The slope returned is the angle from the end point to the beginning point, relative to the vertical of the end point to the center of the earth - i.e. starting at the axis pointing straight down into the earth, how many radians do you have to angle up until you hit the starting point. The DTED elevation of the end point is gathered from the dted cache.

Parameters:

startLLP - the coordinates of point 1.

startTotalHeight - the total height of point 1, from the Mean Sea Level - so it's the elevation of the point plus altitude above the surface, in meters.

endLLP - the coordinates of point 2.

endObjHeight - the elevation of point 2 above the surface, in meters. The surface elevation of the point will be looked up and added to this value.

Returns:

slope of line between the two points, with zero pointing straight down, in radians.

calculateLOSSlope

public static double calculateLOSSlope(int startTotalHeight,
                                       int endTotalHeight,
                                       double arc_dist)

Calculate the slope of a line between two points across a spherical model of the earth. A slope of zero is pointing to the sky from the starting point. 90 degrees is perpendicular from that start point vector, which would be the slope of two points next to each other of the same height. Any angle greater than than and you're rolling downhill.

Parameters:

startTotalHeight - total height of one point, in meters. Should represent elevation of point which is the surface elevation above MSL, and the height above the surface.

endTotalHeight - total height of one the other point, in meters. Should represent elevation of point which is the surface elevation above MSL, and the height above the surface.

arc_dist - the surface angle, in radians, across the spherical model of the earth that separates the two points.