Questions tagged [slam]

SLAM (Simultaneous Localization And Mapping) refers to a robot building a map of its environment through it's sensor data (mapping) and keeping track of its own position in that map (localization) at the same time.

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How to get 2D map using Stereoscopic camer (RGB+D), IMU and GPS?

I am starting with slam using imu, stereo camera (that gives RGB + depth info) camera and gps mounted on my robot. I wish to create a 2D map for it like this: But with landmarks, so that I can stop ...
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Improvements over FastSLAM2.0

Are there some papers and/or works that describe improvements for the FastSLAM2.0 algorithm? I'm particularly interested in the following areas: The map is completely unknown at the beginning of the ...
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Scale drift correction in monocular ORB-SLAM2

Trying to correct scale drift in monocular ORB-SLAM2, but leads to multiple track loss events (for instance, track lost on KITTI 03 around 5-6 times). Using the scale correction method as described by ...
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When a permutation matrix is desired for transforming camera frame to world frame?

When dealing with rectified images, why would the inverse of a simple permutation matrix $$P = {\begin{bmatrix} 0 & -1 & 0 \\ 0 & 0 & -1 \\ 1 & 0 & 0 \end{bmatrix}}^{-1}$$ ...
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How does isam compare with Gmapping and Hector?

I read about incremental smoothing and mapping (iSAM) first in the paper on hector_slam (a flexible and scalable SLAM system with full 3D motion estimation by Stefan Kohlbrecher et al) and then read ...
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How to deal with Gaussian Errors, which don't have a mean value of 0?

I'm writing a SLAM algorithm. One of the main problems is, that the landmark measurement error is not really Gaussian distributed, which means, their error doesn't have a mean value of 0. I already ...
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Transforming a 3x3 Covariance Matrix to 2x2

Hello friends of the robotics, for Data Association I have the Robots cov matrix in a 3x3 Form, but the measurements and landmarks only in 2x2. I want to compute the Mahalanobis distance, so how ...
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Triangulation: Ceres solver minimizes only the last residual block

I have been attempting to estimate a bunch of 3d coordinates viewed via a multi-view setup with known poses, I have the code running, but the output of ceres seems baffling. There are 7 image frames/...
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Estimate noise covariance matrix of measurements using a ros-bag

I am facing the following issue, and some hint or orientation would be great. I am working on a project in which I was given a ROS bag, and I have to implement a localization node using SLAM. To do so,...
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How does loop closure backpropagate the robots states into prior times?

I have read some about loop closure and I am somewhat confused. Suppose we implement something like EKF slam using LIDAR and suppose loop closure is aided by computer vision based features so that if ...
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How to correctly use [VertexSE3Expmap] as two connecting Vertex in Edge_V_V_GICP?

I am working on a pose estimation problem solved by Levenberg-Marquardt with g2o. I want to build 3D rigid constraint between two pose, so I choose Edge_V_V_GICP and test the g2o/examples/icp/...
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Should I wrap the intrinsic and extrinsic parameters to a single vector during optimization?

I've read the libmv library dedicated to solving the bundle adjustment problem. The author states it's better to wrap the rotation and translation parameters into a single vector during optimization ...
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What does the normalized image coordinates imply?

In VSLAM or visual odometry, we use a camera matrix P to transform 3D scene points to 2D image points. When using homogeneous representation, we may choose the image coordinates as the normalized ...
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Does every rotation vector has an one-to-one corresponding rotation matrix?

Given a rotation vector, can we always get the same corresponding rotation matrix computed by the Rodrigue's rotation formula?
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Applying Rotation & Translation Matrix Obtained from Iterative Closest Point

Suppose I have M lidar contour points from t = k and N lidar contour points from t = k+1. (Some of you might question why I have differing number of contour points, and the reason is that these lidar ...
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Can someone share with me some modern review paper about the filter-based SLAM?

I'm currently learning the Visual SLAM. But I'm also very curious about the modern filter-based SLAM. Can someone share with me some modern review papers about it?
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How is the depth estimation done in DTAM / LSD-SLAM (direct VSLAM)?

I know that DTAM and LSD-SLAM both employ the photometric error between two keyframes to estimate the image depth. But I don't know what the photometric error describes precisely. In the DTAM paper, I ...
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How do you handle angle discontinuities in estimation problems?

When one is implementing a state estimator in a system that involves kinematics, will inevitably face the problem of angle discontinuities, i.e., the fact that the angles have to be wrapped between ...
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Occupancy grid maps

Why do we take probabilistic approch to model the environment for robots in occupancy grid maps.The assumption is always taken that each cell on the grid map is either free or occupied.So why have ...
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ICP(Iterative Closest Point) with Partially Overlapping Conditions & Changing Point Numbers

I am currently working on fixing vehicle odometry data using lidar contour points. Since I am receiving lidar data in the form of countour points, I thought I'd use ICP to correct the odometry error ...
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Vehicle Odometry Correction Using Lidar Contour Points (Localization)

I am currently working on a project where... Vehicle travels from point A to B GPS trajectory is used as a reference Vehicle odometry (bicycle model without slip angle beta) was used to estimate a ...
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Compute path in absolute frame from sequence of measurements

I have a sequence of measurements $\{(x_i, y_i, \theta_i)\}_{i = 1 \:...\: N}$. Each of these represents the new pose of the robot seen from the previous pose, i.e. a measurement $(x', y', \theta')$ ...
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Motion model and homogeneous transformation issue on a drone

I am trying to develop a EKF-SLAM algorithm for a drone, and I want to estimate its position in the inertial/world reference frame. I have as control variables the linear and angular velocities in the ...
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Are there some papers or books that compactly elaborate the essential part of the multiple view geometry?

I am a novice to visual SLAM and computer vision. Recently I've read a paper "A micro Lie theory for state estimation in robotics" dedicated to introducing the essential part that necessary to ...
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Robot Localization - Motion and Sense Probability

I'm currently taking Udacity's AI for robotics course and came across a question that stumped me. The problem plays on localization probability given uncertainty in our measurement updates. The first ...
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Caculate/Specify the covariance matrix for a omniwheel robot

I have an omnidirectional robot (x, y and rotation around z), which I would like to use the SLAM-algorithm from ROS. But the odometry from the robot has a drift, which makes some error. To improve the ...
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Bundle Adjustment for Monocular SLAM

I am confused with how monocular BA works in visual-based SLAM. Is there any tutorials I can do in openCV to provide me some visualization aid? Thank You.
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EKF-SLAM what should the observation model be?

I am implementing an EKF algorithm for a drone localization, and while I was defining the observation model I got a bit confused. This is my situation: I have a drone which is able to give me the ...
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What is the concepts of submaps in LIDAR based graph slam algorithms?

I have been reading some slam papers recently and many of the papers mention building and performing scan matching on submaps instead of individual poses. Does it mean that a submap is just a single ...
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Which math books would help in learning SLAM systems? [closed]

Recently I started studying papers on SLAM systems by Durrant-Whyte for my research and I'm finding some difficulties in the math (matrices and probability) that is tackled in these papers. Which ...
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Guidance on SBC for Visual-Based SLAM [closed]

Intro: I am a student that just started a project regarding prototyping a mobile robot that involve Indoor SLAM implementation. I am very new to the field of computer vision, SLAM and SBC (single ...
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Applying initial guessing to LiDAR point cloud for ICP processing in Graph SLAM

I am currently in the process of implementing Graph SLAM using ICP and g2o in python 2.7 The data I have are pose data (4 x 4 transformation matrix) and lidar data ( in the format of [x y z 1] with ...
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How does a recursive Bayesian depth filter is used to build a map in visual odometry?

I am trying to understand a paper on visual odometry and I am having troubles understanding how a map is generated using a stereo camera as sensor. The paper I am reading is SVO: Semi-Direct Visual ...
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On the covariance matrix of the EKF SLAM

In the covariance matrix of the EKF SLAM, there are components that specifies the correlation between landmarks. Are those values important? Because while we bulding map of landmarks, we only draw the ...
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Dual constraint non-linear optimization for SLAM

I am trying to achieve a nonlinear optimization for SLAM on a function that contains two different constraints, like this : $$ T_{opt} = \underset{T}{\arg\min} \sum_i(\left\lVert T.X_i - x_i \right\...
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Good Software Projects for Aspiring Engineers [closed]

With the pandemic going on, our school has decided to officially shutdown all sponsored club meetings. Now that we are all digital, our robotics club was looking for projects that students can do at ...
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Difference between SLAM and Localization

What are the differences between SLAM and Localization if you have a known map? How does the position probability update differ between the two? In particular I'm curious on if localization is a ...
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What are the limitations of RatSLAM?

I recently read about RatSLAM, a visual SLAM implementation that only needs a simple monocular webcam to map and localize, instead of the usual high precision range finders and encoders that most SLAM ...
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Object Avoidance Using Intel Realsense

Are there any open source projects that use intel realsense for object avoidance and navigating to a destination?
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Intel Realsense Cameras for Object Avoidance and SLAM to go to destination

My goal is to make a UAV which can search an area while avoiding obstacles. I figured I would navigate using the SLAM and Intel Realsense D435i (a stereoscopic camera with an IMU built in), but all of ...
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Uncertainty in grid based fastslam

Given I am building a grid map, and poses are represented using particles, how can I calculate the uncertainty of a pose In a grid based fastslam 2.0?
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loop closing in grid based fastslam 2.0

I understand how grid based fastslam 2.0 works I just would like to know how to implement a loop closure functionality in a grid-based fastslam 2.0? Since at each state we only consider the last state ...
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What Software Is Used For Autonomy Software Simulation?

I don't have a physical robot but I would like to test the performance of my C++ code for odometry, SLAM, and path planning. Are there any good simulation software where I can test my algorithm ...
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How to derive the camera trajectory from ICP

This may be a very simple question so please bear with me... Suppose I have a stationary object and point clouds, $n$ $(x,y,z)$ points, of that object taken by a moving camera at time steps $t_i$, $...
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Rescaling a local Map in VSLAM (orb slam)

I am trying to inject metric scale into a vslam algorithm, namely the popular ORB-SLAM2. I have read several papers(1,2) whereby people have successfully calculated scale factor from the actual height ...
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Can standard SLAM techniques be used in maritime environments, where waves and currents move the vessel even with no control input

I am trying to implement a functioning SLAM system for an autonomous surface vessel (ASV). I don't have any direct experience with SLAM, and I am therefore researching the topic before I try to ...
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Hector_Slam orientation probelm for drone

We are using Hector slam(2-D Mapping) for our drone in which we are facing some problems 1) as the orientation(axis) of the lidar changes the orientation of map changes 2) as the plane of the lidar ...
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Ceiling Camera & robot - SLAM still neded?

I've got a question regarding the topic of SLAM. My composition consists of a mobile robot and a top down looking 2D camera with wide-angle lens. It is comparable to a survaillance camera mounted on ...
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Is SLAM done only first time in a given environment

I am training Turtlebot 2 to move around the office. I come from robotics hardware background but relatively new to computer vision and robotic mapping. Here are my two fundamental questions related ...
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How does scan matching find overlapping regions in two scans?

I have been reading about scan matching and so far I have gathered that scan matching tries to find the transformation (rotation and translation) which leads to the best match between overlapping ...

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