clarify distance calculation

Signed-off-by: Maxime CLEMENT <maxime.clement@tier4.jp>

Author: maxime-clem

planning/behavior_velocity_dynamic_obstacle_stop_module/src/object_filtering.cpp

@@ -67,10 +67,11 @@ std::vector<autoware_auto_perception_msgs::msg::PredictedObject> filter_predicte
     const auto opposite_heading = yaw_diff > M_PI_2 + M_PI_4;
     const auto collision_distance_threshold =
       params.ego_lateral_offset + o.shape.dimensions.y / 2.0 + params.hysteresis;
-    auto has_collision = std::abs(
+    // https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line#Line_defined_by_point_and_angle
+    const auto lat_distance = std::abs(
                            (o_pose.position.y - ego_data.pose.position.y) * std::cos(o_yaw) -
-                           (o_pose.position.x - ego_data.pose.position.x) * std::sin(o_yaw)) <=
-                         collision_distance_threshold;
+                           (o_pose.position.x - ego_data.pose.position.x) * std::sin(o_yaw));
+    auto has_collision = lat_distance <= collision_distance_threshold;
     if (ego_data.earliest_stop_pose) {
       const auto collision_at_earliest_stop_pose =
         std::abs(