Addition: Define units for accuracy (#162)

As with altitudeAccuracy, implementations provide this value in meters
but this was not specified.

Fixed #160.

index.html

@@ -1138,13 +1138,19 @@ <h4>
           according to the [[WGS84]] geodetic system, instead of just stating
           "decimal degrees."
         </aside>
+        <aside class="addition" id="a3">
+          <span class="marker">Candidate Correction:</span> To improve clarity
+          and precision, a description of the accuracy attribute has been added,
+          defining it as meters of radius.
+        </aside>
         <p>
           <del cite="#c3">The <strong>latitude</strong> and
           <strong>longitude</strong> attributes are geographic coordinates
           specified in decimal degrees.</del> <ins cite="#c3">The
           <dfn>latitude</dfn> and <dfn>longitude</dfn> attributes denote the
           position, specified as a real number of degrees, in the [[WGS84]]
-          coordinate system.</ins>
+          coordinate system.</ins> <ins cite="#a3">The <dfn>accuracy</dfn>
+          attribute denotes the position accuracy radius in meters.</ins>
         </p>
       </section>
       <section>