Show area cover based on lineString

Question

What I am trying to do is display the area covered by someone. For example a search team walks through a field, a person could see roughly 50m either way. So I would want to display essentially a polygon with the width of 100m and the length of the path that has been walked. I would need to both display this graphically and in an area measurement.

The best idea I have to implement this is to create a line string and then create a polygon from that by somehow setting the points 90 degrees from the line of point A to point B. Something like this:

         |                 |
         |                 |
Point A  +-----------------+ Point B
         |                 |
         |                 |

However, I have no idea how I would get an angle from the line in order to find the coordinates to create the polygon. Does anyone know of a way to do this?

Answer 1

I found the solution eventually. Basically you need to use ol.geom.Polygon.fromCircle. If you set the number of points to 2 it will give you a horizontal line which you can rotate to the heading direction.

var theCircle = new ol.geom.Circle(theMarker.getCoordinates(), Radius);
var polyCircle = new ol.geom.Polygon.fromCircle(theCircle, 2, heading);
var polyCircleCoords = polyCircle.getCoordinates();

Answer 2

Take a look at this example.

I use this function to generate the coordinates:

function rotate(xCoord, yCoord, angle, length) {
    length = typeof length !== 'undefined' ? length : 10;
    angle = angle * Math.PI / 180; // if you're using degrees instead of radians
    return [
        length * Math.cos(angle) + xCoord, 
        length * Math.sin(angle) + yCoord
    ];
}