# Setting up ethzasl_sensor_fusion with PTAM

Hi, I have a very basic question. When using ethzasl_sensor_fusion, you need to set it up by setting the callback function in ssf_updates to have an input wich matches the message type of the position from PTAM, and also set the position function in ssf_updates to have a matching member type as this functions input. I believe I'm doing this wrong becouse when I run the program I get === ERROR ===prediction p: NAN at index 0 . Has anyone set this up can anyone tell me what the used for they callback function? I curently am using const geometry_msgs::PoseWithCovarianceStamped as the inputto my callback function, becouse, using the rqt topic analyser, thats what I think the output from PTAM is, and I have the following for the position function

z_p_ = Eigen::Matrix<double,3,1>(msg.pose.pose.position.x, msg.pose.pose.position.y, msg.pose.pose.position.z);