Mention preservation of significant figures in the man page.

Author: dfandrich

doc/gpscorrelate-manpage.xml.in

@@ -198,7 +198,9 @@
     <para> If GPS data are available at the precise moment the image was taken
       (with a 1-second granularity) the GPS data are stored unmodified in EXIF
       fields. If they are not, linear interpolation of GPS data available at
-      moments before and after the image was taken can be used. </para>
+      moments before and after the image was taken can be used.  A measure of
+      the approximate accuracy of the GPS location reading is preserved when
+      written into the image.</para>
 
   </refsect1>
   <refsect1>