@NonNull
    public Viewport resize(final double factor) {
        return new Viewport(getCenter(), getLatitudeSpan() * factor, getLongitudeSpan() * factor);
    }
Return a widened or shrunk viewport.

@param factor multiplicative factor for the latitude and longitude span (> 1 to widen, < 1 to shrink)
@return a widened or shrunk viewport
main/src/main/java/cgeo/geocaching/location/Viewport.java