Added Dot method to Vector

Observer.cpp

@@ -75,9 +75,7 @@ CoordTopographic Observer::GetLookAngle(const Eci &eci) {
         az += 2.0 * Globals::PI();
 
     double el = asin(top_z / range.GetW());
-    double rate = (range.GetX() * range_rate.GetX() +
-            range.GetY() * range_rate.GetY() +
-            range.GetZ() * range_rate.GetZ()) / range.GetW();
+    double rate = range.Dot(range_rate) / range.GetW();
 
     /*
      * azimuth in radians

Vector.cpp

@@ -14,3 +14,10 @@ Vector Vector::Subtract(const Vector& vec) const {
             z_ - vec.z_,
             0.0);
 }
+
+double Vector::Dot(const Vector& vec) const {
+
+    return (x_ * vec.x_) +
+            (y_ * vec.y_) +
+            (z_ * vec.z_);
+}

Vector.h

@@ -54,7 +54,8 @@ public:
     }
 
     double GetMagnitude() const;
-    Vector Subtract(const Vector& v) const;
+    Vector Subtract(const Vector& vec) const;
+    double Dot(const Vector& vec) const;
 
 protected:
     double x_;