Hi Martin,
Yes, I think so, basically you are suggesting the same thing I use. The code
for which is below:
/**
* @param a_Point2D
* @param b_Point2D
* @param distance
* @return Point2D which lies in a straight line in the direction from
* a_Point2D to b_Point2D and which is distance units from a_Point2D
*/
public static Point2D getPoint2D(
Point2D a_Point2D,
Point2D b_Point2D,
double distance) {
Point2D result = null;
double angle = a_Point2D.getAngle(b_Point2D);
double xdiff = Math.sin(angle) * distance;
double ydiff = Math.cos(angle) * distance;
BigDecimal x = a_Point2D._x.add(new BigDecimal(xdiff));
BigDecimal y = a_Point2D._y.add(new BigDecimal(ydiff));
result = new Point2D(
x,
y,
a_Point2D._DecimalPlacePrecision);
return result;
}
/**
* Imprecise
* @param a_Point2D
* @return Angle to the y axis clockwise. Default 0.0d.
*/
public double getAngle(Point2D a_Point2D) {
double dx = a_Point2D._x.doubleValue() - _x.doubleValue();
double dy = a_Point2D._y.doubleValue() - _y.doubleValue();
if (dy == 0.0d) {
if (dx == 0.0d) {
return 0.0d;
} else {
if (dx > 0.0d){
return Math.PI / 2.0d;
} else {
return (3.0d * Math.PI) / 2.0d;
}
}
} else {
if (dy > 0.0d){
if (dx == 0.0d) {
return 0.0d;
} else {
if (dx > 0.0d){
return Math.atan(dx / dy);
} else {
return (2.0d * Math.PI) - Math.atan(Math.abs(dx) / dy);
}
}
} else {
// dy < 0.0d
if (dx == 0.0d) {
return Math.PI;
} else {
if (dx > 0.0d){
return Math.PI - Math.atan(dx / Math.abs(dy));
} else {
return Math.PI + Math.atan(Math.abs(dx) / Math.abs(dy));
}
}
}
}
}
Best wishes,
Andy
http://www.geog.leeds.ac.uk/people/a.turner/
From: Martin [mailto:[email protected]]
Sent: 08 April 2010 11:38
To: [email protected];
[email protected]
Subject: [Geotools-gt2-users] How to calculate a Point given another point, a
distance and a angle?
Hi all,
I know this is not a typical question for a user list but I least I can try to
find help here;-)
I have given a vehicle (it's a point) and the movementpath of the vehicle (it's
a "directed" linestring) ! I computed the degree of the movement!
For example moving from
(0,0) to (0.5) the movement direction is/has 0 degree
(0,0) to (5.0) the movement direction is/has 90 degree
(0,0) to (0.-5) the movement direction is/has 180 degree
(0,0) to (-5.0) the movement direction is/has 270 degree
but for visualization each vehicle occupies a rectangle and I want to compute
the position of the rectangle "!beneath!" the street!
So I have given a point(vehicles point on the streetnetwork) the
movementdegree and the distance(width of the rectangle/2)!
And I need to compute the point!
(situation is shown in attachment)
My idea is for computing the point (x,y) is:
x = sin(degree)* distance + x(value of point on street)
y = cos(degree)*distance+y(value of point on street)
What do you say? Is the formular correct?
Cheers,
Martin
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