Precision of SVG coordinates?

Question

Does anyone know the "official" precision of SVG coordinates in browsers?

For example: If I draw an arc with almost 360° it will eventually disappear because start and end are collapsing.

<svg version="1.1" xmlns="http://www.w3.org/2000/svg">
    <style>
        path {
            stroke-width: 10px;
            stroke: black;
            fill: none;
        }
    </style>
    <path 
        d="
        M 200 200
        A 100 100 0 1 1 199.99999 199.99999"
    />
</svg>

draws a perfect circle (in Firefox 34). However, adding a 9 to 199.99999 yields to nothing being drawn. Is this behavior specified anywhere?

Answer 1

The SVG specification says double precision. No UA implements this though because they are all constrained by platform capabilities such as direct3d which are generally single precision.