Hector mapping not creating map

Hi, I have a LIDAR connected to an AR drone, with drivers running on the drone to read the laser data, and send it to my ros master computer using netcat. I have written a ros driver in python that listens to the network and reads the incoming laser data, creates a LaserScan message, populates all the fields and then publishes this to /scan. I can see /scan in rostopic list, and can see populated messages in rostopic echo /scan. However when I run my launch file which runs hector_mapping, no map is created. I know the launch file works as I have tested it with the LIDAR connected directly to the master computer using the official drivers and it builds a map fine. So I think there must be a problem when I populate the LaserScan message and publish it. I have included one of my populated messages below, can anyone see anything wrong with it or suggest something else which I can try? I have noticed the seq fields in the header are always 0 but have read I shouldn't set that myself and leave ros to deal with it. Node: /laserlistener Time: 21:56:49.521363019 (2016-04-05) Severity: Info Published Topics: /rosout, /scan header: seq: 0 stamp: secs: 1459889809 nsecs: 520699977 frame_id: laser angle_min: 3.14159265359 angle_max: -3.14159265359 angle_increment: 0.0174532925199 time_increment: 0.000515921866295 scan_time: 0.18521595 range_min: 0.15 range_max: 6 ranges: [0.0, 0.0, 1274.25, ... ] omitted as lots of numbers, all look correct though intensities: [ ... ] ditto The angle_min and angle_max fields are meant to be like that (at least that is what the official driver spits out) I have also tried 0 to 2*pi Launch file: Publishing node: #!/usr/bin/env python import roslib; roslib.load_manifest('laserdrone'); import rospy; import math; import tf; from sensor_msgs.msg import LaserScan; import socket; import numpy as np; import time; import sys; if __name__ == '__main__': rospy.init_node('laserlistener'); pub = rospy.Publisher("scan", LaserScan, queue_size=10); rate = rospy.Rate(10); host = ''; port = 44444; sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM); sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1); sock.bind((host, port)); sock.settimeout(15); sock.setblocking(1); sock.listen(0); try: print "Waiting for incoming data for 15 seconds" request, addr = sock.accept(); except: print "timed out" sys.exit(0); print "Connected" angs = []; dists = []; Qs = []; results = [] oldang = -1; lastTime = rospy.Time.now(); while not rospy.is_shutdown(): data = request.recv(10); while (data.find("\n")==-1): data += request.recv(1); #print data; try: line = data.split(","); #90.0, 1000.45, 12 if len(line) != 3: continue; ang = float(line[0].strip()); dist = float(line[1].strip()); Q = float(line[2].strip()); angs.append(ang); dists.append(dist); Qs.append(Q); if(ang < oldang): #publish here print "Publishing now"; thisTime = rospy.Time.now(); duration = (thisTime - lastTime).to_sec(); lastTime = thisTime; print thisTime.secs, thisTime.nsecs, duration; # print thisTime, lastTime, thisTime-lastTime, thisTime.to_sec(); lasermsg = LaserScan(); lasermsg.header.stamp = lastTime; lasermsg.header.frame_id = "laser"; lasermsg.scan_time = duration; lasermsg.time_increment = duration / 359; lasermsg.angle_min = math.pi; lasermsg.angle_max = -math.pi; lasermsg.angle_increment = math.pi / 180; lasermsg.range_min = 0.15; lasermsg.range_max = 6; lasermsg.ranges = dists; lasermsg.intensities = Qs; rospy.loginfo(lasermsg); pub.publish(lasermsg); angs = []; dists = []; Qs = []; oldang = ang; except KeyboardInterrupt: raise except: print "err, data:",data, ", ", sys.exc_info()[0]; rate.sleep(); Many thanks