minor scale change in distance between pixels

include/msckf_vio/feature.hpp

@@ -874,8 +874,14 @@ cv::Point2f Feature::pixelDistanceAt(
                                 cam.distortion_coeffs, 
                                 pure); 
 
-  // returns the absolute pixel distance at pixels one metres away
-  cv::Point2f distance(fabs(pure[0].x - pure[1].x), fabs(pure[2].y - pure[3].y));
+  // transfrom position to camera frame
+  // to get distance multiplier
+  Eigen::Matrix3d R_w_c0 = quaternionToRotation(cam_state.orientation);
+  const Eigen::Vector3d& t_c0_w = cam_state.position;
+  Eigen::Vector3d p_c0 = R_w_c0 * (in_p-t_c0_w);
+
+  // returns the distance between the pixel points in space
+  cv::Point2f distance(fabs(pure[0].x - pure[1].x)*p_c0[2], fabs(pure[2].y - pure[3].y)*p_c0[2]);
 
   return distance;
 }