diff --git a/doc.html b/doc.html
index 1535ace3..f9b3da9d 100644
--- a/doc.html
+++ b/doc.html
@@ -296,8 +296,8 @@
           put<sup><a href="#unzip">3</a></sup> in the <code>DEM</code> directory in one
           of the configuration paths for GPXSee to use them.</p>
 
-          <p>The <a href="https://dds.cr.usgs.gov/srtm/version2_1/SRTM3/">SRTM data</a> is
-          provided for example by the <abbr title="U.S. Geological Survey">USGS</abbr>.</p>
+          <p>The DEM files must have the expected filename format of <code>NXXEYYY.hgt</code>
+          or <code>NXXEYYY.hgt.zip</code> for GPXSee to use them.</p>
 
 
           <div id="footnote">