diff --git a/contours/README.md b/contours/README.md
index 78da407..d2a21b9 100644
--- a/contours/README.md
+++ b/contours/README.md
@@ -16,9 +16,9 @@ but not available outside major cities.
  501991.670  6150000.000  57.689
 ```
 
-**Non-gridded**, therefore significantly slower (`gdal_grid` must be used
-before making contours, which is slow). However, available throughout the
-country.
+2009 variant is less dense, non-gridded, therefore significantly slower
+(`gdal_grid` must be used as an extra step, which is slow). This variant is
+less robust, but available throughout the country.
 
 Usage
 -----