How to merge two laserscans?

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Hello all,

I have two sensors (KInect and asus) and I am able to get laserscan data from both of them. I wrote a simple python script which subscribes to two scan topics and merges into a new scan topic. I wanted to use the newscan to build a map but it is not working as i expected as the newscan has some delay and whenever i try to use this newscan for gmapping it's throwing me an error saying that "extraplotaion error".

Has anyone tried this before? If yes, Can you please help me?

Here is my python script:

#!/usr/bin/env python

import rospy
from sensor_msgs.msg import LaserScan


class extended_scan:

    def __init__(self):

        self.scan_pub = rospy.Publisher('/newScan', LaserScan, queue_size=0)
        self.scan1 = None
        self.scan2 = None

    def laser_1_callback(self, data1):
        # print data1
        # print 'sai'
        self.scan1 = data1

        return self.scan1

    def laser_2_callback(self, data2):
        # print data2
        # print 'sai1'
        self.scan2 = data2

        return self.scan2

    def newScan_pub(self):
        while not rospy.is_shutdown():
            rospy.Subscriber('/camera1/scan', LaserScan, self.laser_1_callback)
            rospy.Subscriber('/camera2/scan', LaserScan, self.laser_2_callback)

            newdata = LaserScan()
            if self.scan1 == None or self.scan2 == None:
                rospy.loginfo('got None data')
                pass
            else:
                newdata.header.seq = self.scan1.header.seq
                newdata.header.stamp = self.scan1.header.stamp
                newdata.header.frame_id = self.scan1.header.frame_id
                newdata.angle_min = self.scan1.angle_min
                newdata.angle_max = self.scan1.angle_max + -(self.scan2.angle_min) + self.scan2.angle_max
                newdata.angle_increment = self.scan1.angle_increment
                newdata.time_increment = self.scan1.time_increment
                newdata.scan_time = self.scan1.scan_time
                newdata.range_min = self.scan1.range_min
                newdata.range_max = self.scan1.range_max
                newdata.ranges = self.scan1.ranges + self.scan2.ranges
                newdata.intensities = self.scan1.intensities
                # print len(self.scan1.ranges)
                # print len(self.scan2.ranges)
                # print len(newdata.ranges)

                self.scan_pub.publish(newdata)
                # rospy.spin()
if __name__ == '__main__':

    rospy.init_node('extended_scan_publisher')
    rospy.loginfo(' starting extended_scan_publishe node')

    ES = extended_scan()
    ES.newScan_pub()
    # rospy.spin()