diff --git a/src/site/markdown/design/digital-elevation-model.md b/src/site/markdown/design/digital-elevation-model.md
index 15e5c29ffd2d66833632f5b4bc4d4a1b4f6663b8..fdf784162fcc7ece5dd9bffdab7af43331e187bd 100644
--- a/src/site/markdown/design/digital-elevation-model.md
+++ b/src/site/markdown/design/digital-elevation-model.md
@@ -26,7 +26,7 @@ a nadir view), some algorithms are more suitable than others. This computation i
 programming unit possible in the Rugged library and an interface is defined with several different
 implementations among which user can select.
 
-Three different algorithms are predefined in Rugged:
+Four different algorithms are predefined in Rugged:
 
  * a recursive algorithm based on Bernardt Duvenhage's 2009 paper
    [Using An Implicit Min/Max KD-Tree for Doing Efficient Terrain Line of Sight Calculations](http://researchspace.csir.co.za/dspace/bitstream/10204/3041/1/Duvenhage_2009.pdf)