Read costmap values from code

edit

Hi,

I would like to read the values from the costmap generated by the robot localization system. This is what I'm doing now:

tf2_ros::Buffer tfBuffer;
tf2_ros::TransformListener tf2_listener(tfBuffer);
costmap_2d::Costmap2DROS costmap_ros("local_costmap", tfBuffer);
costmap_2d::Costmap2D *costmap;


costmap = costmap_ros.getCostmap();

ROS_INFO("OK!");

unsigned int map_x1, map_x2, map_y1, map_y2, index;
double cost1, cost2;

costmap->worldToMap(STATIONS[0][0], STATIONS[0][1], map_x1, map_y1);
costmap->worldToMap(STATIONS[1][0], STATIONS[1][1], map_x2, map_y2);

cost1 = double(costmap->getCost(map_x1, map_y1));
cost2 = double(costmap->getCost(map_x2, map_y2));

But I get this error:

[ WARN] [1611998001.185217756, 4226.344000000]: Timed out waiting for transform from base_link to map to become available before running costmap, tf error: canTransform: target_frame map does not exist.. canTransform returned after 0.1 timeout was 0.1.

I search a lot, but without success. I see the global and local costmaps in RVIZ, but I don't know how to access their values from code.

Can someone help me please?

[EDIT]

I discovered in the source code of the constructor of Costmap2DROS these lines:

    // get our tf prefix
ros::NodeHandle prefix_nh;
std::string tf_prefix = tf::getPrefixParam(prefix_nh);

// get two frames
private_nh.param("global_frame", global_frame_, std::string("/map"));
private_nh.param("robot_base_frame", robot_base_frame_, std::string("base_link"));

// make sure that we set the frames appropriately based on the tf_prefix
global_frame_ = tf::resolve(tf_prefix, global_frame_);
robot_base_frame_ = tf::resolve(tf_prefix, robot_base_frame_);

ros::Time last_error = ros::Time::now();
std::string tf_error;
// we need to make sure that the transform between the robot base frame and the global frame is available
while (ros::ok() && !tf_.waitForTransform(global_frame_, robot_base_frame_, ros::Time(), ros::Duration(0.1), ros::Duration(0.01),&tf_error))

It seems the two frames to be trasformed are hard coded... They does not exist in my framework.