Fixed typos.

src/site/markdown/design/digital-elevation-model.md

@@ -30,7 +30,7 @@ Three 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)
- * an alternate version od Duvenhage algorithm using flat-body hypothesis,
+ * an alternate version of the Duvenhage algorithm using flat-body hypothesis,
  * a basic scan algorithm sequentially checking all pixels in the rectangular array defined by Digital Elevation Model entry and exit points,
  * a no-operation algorithm that ignores the Digital Elevation Model and uses only the ellipsoid.
 

src/site/markdown/design/overview.md

@@ -30,7 +30,7 @@ interpolation ...). The Rugged library itself provides the algorithms
 dealing with line-of-sight intersection with Digital Elevation Models
 in a mission-independent way. Rugged does not parse the DEM models itself,
 nor does it performs image processing. Mission-dependent parts (including
-Digital Elevation Model parsing or instrument viewing model creation remain
+Digital Elevation Model parsing or instrument viewing model creation) remain
 under the responsibility of Rugged caller, typically using a mission-specific
 library used by several image processing applications.