Geometry Engine functions for middlePoint and bearing?

RafaelFreitas

Hello community,

I am currently working with lines on a Java application that requires some geometry processing such the bearing of this line and also the midpoint.
I was browsing the API and couldn't find any implementation of those by myself. There are functions for this that I am missing?

Thanks!

MarkBaird

I'm sure there are many ways of achieving this but I've found the following works.

So lets start with a line and draw it.

// create a purple (0xFF800080) simple line symbol
SimpleLineSymbol lineSymbol = new SimpleLineSymbol(SimpleLineSymbol.Style.DASH, 0xFF800080, 4);

// create a new point collection for polyline
PointCollection points = new PointCollection(SpatialReferences.getWebMercator());

// create and add points to the point collection
points.add(new Point(-302232.417504, 7570568.626755));
points.add(new Point(-294306.469759, 7574158.422559));

// create the polyline from the point collection
Polyline polyline = new Polyline(points);

// create the graphic with polyline and symbol
Graphic graphicLine = new Graphic(polyline, lineSymbol);
graphicsOverlay.getGraphics().add(graphicLine);

Then we get the mid point in 2 steps.  First, you find the length then draw a point along the line at a distance of half that length:

// get start and end points
Point startPoint = polyline.getParts().get(0).getStartPoint();
Point endPoint = polyline.getParts().get(0).getEndPoint();

// get the length in metres
double length = GeometryEngine.distanceBetween(startPoint, endPoint);

// use the length to get the mid point
Point midPoint = GeometryEngine.createPointAlong(polyline, length/2);

// draw the mid point
SimpleMarkerSymbol sms = new SimpleMarkerSymbol(SimpleMarkerSymbol.Style.CIRCLE, 0xFF00FF00,10);
Graphic intersectGraphic = new Graphic(midPoint, sms);
graphicsOverlay.getGraphics().add(intersectGraphic);

Calculating the bearing can be done using basic geometry, but note this will only work with a projected coordinate system.

// working out the bearing of the line.
double xDiff = endPoint.getX() - startPoint.getX();
double yDiff = endPoint.getY() - startPoint.getY();

// get the angle

double angleRad = Math.atan(xDiff/ yDiff);
double angleDeg = Math.toDegrees(angleRad);

System.out.println("angle " + angleDeg);

Does this help?