Conversion into ROS compatible timestamp

asked 2011-10-27 05:01:46 -0600

alfa_80
1051 ●123 ●137 ●150

updated 2011-10-28 08:50:53 -0600

I was following a tutorial on laser scanner. But then, there is time-related stuff that I need to modify so that the time is not considered taken real-time(as shown in tutorial, it uses

ros::Time scan_time = ros::Time::now();
scan.header.stamp = scan_time;

to realize it. Instead, I want to take time values from a dataset(logfile).

I've tried to do as the following:

for (int i = 0; i < num_row; i++)
{
    scan.header.stamp =  data_set[i][1];
}

but, it doesn't work..for the line "scan.header.stamp = data_set[i][1];", I receive the following error:

"no match for ‘operator=’ in ‘scan.sensor_msgs::LaserScan_<std::allocator<void>     >::header.std_msgs::Header_<std::allocator<void> >::stamp = (((std::vector<double,     std::allocator<double> >*)((PointCloud*)this)-
 >PointCloud::data_set.std::vector<_Tp, _Alloc>::operator[] [with _Tp =     std::vector<double, std::allocator<double> >, _Alloc = std::allocator<std::vector<double,     std::allocator<double> > >](((long unsigned int)i)))->std::vector<_Tp, 
 _Alloc>::operator[] [with _Tp = double, _Alloc = std::allocator<double>](1ul) / 1.0e+3)’"

I cannot see the culprit..

answered 2011-10-27 05:20:14 -0600

dornhege

31395 ●134 ●284 ●498

Check out the constructors in the ROS Time API.

You can either pass in a Time in seconds (as double) or the single components directly - both as unix timestamp.

What you need depends on the datatype of your data_set.

edit flag offensive delete link

Comments

The time in my dataset is in milliseconds, that means I need to convert it to seconds, am I right that way? It is in int, I perhaps can just type-cast it to double..

alfa_80 ( 2011-10-27 06:03:48 -0600 )edit

The two argument constructor takes seconds and nano seconds. That's likely the easiest way to use your number.

tfoote ( 2011-10-27 13:55:14 -0600 )edit

@tfoote: I've tried to use the one takes 2 constructor like this: "scan.header.stamp = ((data_set[z][1])/1000, (data_set[z][1])*pow(10,6)) ;", but then it says that "value computed is not used" on that line of code.

alfa_80 ( 2011-10-27 15:42:13 -0600 )edit

It seems OK now, but is it true just to convert like that? I input those 2 "identical" arguments in s and ns? I have only one timestamp anyway in my dataset..

alfa_80 ( 2011-10-27 15:55:52 -0600 )edit

got error: error: no match for ‘operator=’ in ‘scan.sensor_msgs::LaserScan_<std::allocator<void> >::header.std_msgs::Header_<std::allocator<void> >::stamp = (((void)(((std::vector<double, std::allocator<double> >*)((PointCloud*)this)->PointCloud::data_set.std::vector<_Tp, _Alloc>::operator[] [with _

alfa_80 ( 2011-10-27 16:02:30 -0600 )edit

When using the the two argument constructor, the nsec parameter represents the microseconds component of time, ie. it is always smaller than 1e9, so if you want to pass 1.5 seconds, it would be: sec=1, nsec=5e8 (and not nsec=1.5e9).

Adolfo Rodriguez T ( 2011-10-27 19:37:36 -0600 )edit

Thanks a lot, it now works, the problem is because I don't pass the input argument to the the constructor of the object..

alfa_80 ( 2011-10-28 01:53:50 -0600 )edit

add a comment

Conversion into ROS compatible timestamp

1 Answer

Comments

Question Tools

Stats

Related questions

Conversion into ROS compatible timestamp edit

1 Answer

Comments

Question Tools

Stats

Related questions

Conversion into ROS compatible timestamp