ui/src/main/java/ucar/nc2/ui/geoloc/Rubberband.java
public boolean anchor(Point p) {
    firstStretch = true;
    anchorPt.x = p.x;
    anchorPt.y = p.y;

    stretchedPt.x = lastPt.x = anchorPt.x;
    stretchedPt.y = lastPt.y = anchorPt.y;

    return true;
  }
public boolean anchor(Point p) {
    firstStretch = true;
    anchorPt.x = p.x;
    anchorPt.y = p.y;

    stretchedPt.x = lastPt.x = anchorPt.x;
    stretchedPt.y = lastPt.y = anchorPt.y;

    return true;
  }
Set the anchor point.