From 634769e9d02b1a5f07ade23075bdf899ce667d7c Mon Sep 17 00:00:00 2001 From: Damon Kohler Date: Fri, 29 Sep 2017 16:06:34 +0200 Subject: [PATCH] Adds two new FAQ entries. (#515) --- docs/source/faq.rst | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/docs/source/faq.rst b/docs/source/faq.rst index f92bc04..be13c49 100644 --- a/docs/source/faq.rst +++ b/docs/source/faq.rst @@ -16,8 +16,8 @@ Frequently asked questions ========================== -The laser data in the 3D bags is much higher than the maximum reported 20 Hz rotation speed that the VLP-16 can do. Why? ----------------------------------------------------------------------------------------------------------------------- +Why is laser data rate in the 3D bags higher than the maximum reported 20 Hz rotation speed of the VLP-16? +---------------------------------------------------------------------------------------------------------- The VLP-16 in the example bags is configured to rotate at 20 Hz. However, the frequency of UDP packets the VLP-16 sends is much higher and independent of @@ -35,8 +35,8 @@ enough for roughly 2 revolutions, one per VLP-16. __ https://github.com/googlecartographer/cartographer_ros/blob/master/cartographer_ros/configuration_files/backpack_3d.lua -Why is IMU data required for 3D SLAM, but not for 2D? ------------------------------------------------------ +Why is IMU data required for 3D SLAM but not for 2D? +---------------------------------------------------- In 2D, Cartographer supports running the correlative scan matcher, which is normally used for finding loop closure constraints, for local SLAM. It is computationally expensive but can often render the incorporation of odometry or IMU data unnecessary. @@ -51,3 +51,16 @@ To properly world align the resulting trajectory and map, gravity is used to def 2. Roll and pitch can be derived quite well from IMU readings once the direction of gravity has been established. This saves work for the scan matcher by reducing the search window in these dimensions. + +How do I build cartographer_ros without rviz support? +----------------------------------------------------- + +The simplest solution is to create an empty file named `CATKIN_IGNORE`__ in the `cartographer_rviz` package directory. + +__ http://wiki.ros.org/catkin/workspaces + +How do I fix the "You called InitGoogleLogging() twice!" error? +--------------------------------------------------------------- + +Building `rosconsole` with the `glog` back end can lead to this error. +Use the `log4cxx` or `print` back end, selectable via the `ROSCONSOLE_BACKEND` CMake argument, to avoid this issue.