curved line: 
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https://jsfiddle.net/medmunds/sd10up9t/
http://blog.openwebsolutions.in/how-to-create-curved-line-in-google-map/
geodesic polyline


draw arc: https://stackoverflow.com/questions/24956616/draw-circles-arc-on-google-maps
semi-circle: http://www.geocodezip.com/v3_polygon_example_arc.html


https://www.codeproject.com/Questions/564198/googleplusmapplusapiplusv3plus-3aplusupdateplusrec