Elliptical Arches

There are a couple of techniques for drawing an ellipse

The string Method can be viewed here https://www.google.com/search?q=how+to+draw+an+ellipse+with+string&rlz=1C1CHBF_enGB882GB882&oq=How+to+draw+an+ellipse&aqs=chrome.2.0l8.9902j0j8&sourceid=chrome&ie=UTF-8#kpvalbx=_eBf_Xt_xI_Ca1fAPt_mQsAw49

The method that is extremely simple too, but based on the parametric coordinates of an ellipse can be viewed here https://www.youtube.com/watch?v=Jjh_ZRhfnDY

The method to construct a semi-elliptical curve, an approximation to an ellipse, can be found under Construction Tips. It uses three different centres as spring points for circular arcs, but locating the third centre requires an accurate construction in order to model an ellipse. Below is an arch constructed using this method.