diff --git a/trick_sims/SIM_cannon_analytic/README.md b/trick_sims/SIM_cannon_analytic/README.md
index 2a88aa1d..def67196 100644
--- a/trick_sims/SIM_cannon_analytic/README.md
+++ b/trick_sims/SIM_cannon_analytic/README.md
@@ -10,7 +10,7 @@ velocity subject to the following assumptions and limitations:
 * The **only** force acting on the cannon ball is gravity.
 * The acceleration of gravity (g) is constant and equal to -9.81 meters per
   second squared.
-* The ground is flat, and here, defined as where y=0.
+* The surface of the ground is defined as where y=0.
 
 ![X(t) = Vx * t + X0](images/CannonInit.png)
 
diff --git a/trick_sims/SIM_cannon_analytic/images/CannonInit.png b/trick_sims/SIM_cannon_analytic/images/CannonInit.png
index 404ff6c7..3b24b297 100644
Binary files a/trick_sims/SIM_cannon_analytic/images/CannonInit.png and b/trick_sims/SIM_cannon_analytic/images/CannonInit.png differ