The expected topic name for the cartographer seems to be landmark not landmarks even tough a list of landmarks is expected.

For every trajectory, writes tf
        FLAGS_parent_frame --> trajectory_`trajectory_id`

Without this, it might look like the processing hangs.

* Don't run final optimization in visualize_pbstream.launch

Replaces the offline node with the normal node.

The problem is that the offline node immediately runs a final
optimization with `visualize_pbstream.lua`, which is most likely not the
configuration that was used to generate the pbstream. This can lead to
effects like distortions in the map e.g. due to different weights, even
though the actual saved state is fine.

* Drop all /echoes or /imu messages.

* Use -start_trajectory_with_default_topics=false

Surprising that this has not lead to any issues yet. 
This just works by chance on other systems if QT has been find_packaged before.

Fixes also the other flag descriptions.

* Consider waiting trajectories with a sensor bridge as active.

Fixes a corner case where trajectories that didn't start SLAMing yet
couldn't be finished, e.g. due to waiting for sensor data. They don't
appear in the trajectory states list of the pose graph yet but already
have a trajectory builder.

https://github.com/googlecartographer/cartographer/issues/1367

This fixes #1050. Tested standalone compilation and with the debian fakeroot tool. I had to build with a custom Protobuf3 instance though, so another build-check on a regular setup would be appreciated.

Before this change all *.cc files would be included. If subprojects
were run individually with the Debian package generator. This resulted in an
inclusion of temporarily checked out *.cc from the abseil include. This
change fixes the import behaviour and enables the creation of a valid
package.

* Update /write_state call in assets writer docs.

Follow-up to #966
Closes #1086

* typo

* bump googlebot

This restructures the doc as a tutorial leading newcomers to becoming experimented users.

It adds pages on:
 - how to get started with Cartographer on a new .bag
 - how Cartographer works and can be tuned step-by-step
 - how to use "extra" features of Cartographer
 - how to contribute to Cartographer

It also provides some cosmethic changes with: new titles, non-indented code blocks, various illustrations, reworked paragraphs for clarity...

See `./publish_fake_random_landmarks.py --help` for documentation.

* Transform landmark poses to the tracking frame.

* Address the comment.

Follow-up to #715, spotted by @CccYunxiao, see #1031.

Add documentations related to the feature introduced in #940.

With two 20 Hz lidars and a 200 Hz IMU, the progress reports were outputted every 500 seconds, which is really too sparse to be useful. Decrease this by a factor of 10.

Fixes strange behavior with empty leftover entries in the trajectory list of the RViz plugin.

By using an `std::map` instead of an `std::vector` for the trajectories  we can
easily erase trajectories which do not appear in the submap list anymore.

reading variable 'submap_slices_' requires holding mutex 'mutex_' [-Wthread-safety-analysis]

Useful for debugging with gdb or profiling, e.g. with perf.

Fixes double logging to stderr and rosout and makes it consistent with other
cartographer_ros nodes.

As @ojura reported and explained in #940, there is a critical issue with the new changes introduced in the mentioned PR, which significantly slows down the offline node. 
- The reason of this problem was that In order to count the number of processed messages the `std::distance` function was used which is computationally expensive(O(n)).
- Instead, the former `log_counter_` and now `message_counter_` class variable which was used to print a message every X seconds is also employed to count the number of the processed (and also skipped) messages.

Fixes empty splits for default "" arguments. Follow up to #1026, thx to @ojura.

We have already a cloned source space in the base image, which can be
buggy according to: https://github.com/vcstools/wstool/issues/77

This should unblock Travis and fix local builds.

code simplification

Set the visibility in he constructor, otherwise the setting won't have
an effect on newly created submap slices unless it's toggled again.
Somehow this got lost in #1012, sorry for that.

...and use `LoadStateFromFile` from `MapBuilderStub`. The `LoadState` stub
that's used in `Node::LoadState` streams the state file instead, which can now
be used by explicitly setting the `--upload_load_state_file` flag.

Solves problems with the gRPC message size limit when loading large state files.

The roslaunch API throws an exception if setting the argument but not using it. 
This now forces any including launch files to provide an argument for it, even if it might not be used in the `no_rviz` case.

And adapting offline_backpack_(2d|3d).launch to use it.

This will be useful for parametrizing evaluation runs as well.