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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16 views

RGBD velocity estimation + IMU fusion

What is the best way to estimate velocity from camera in order to do IMU fusion? The simplest is just to take a difference in positions but is there a better way?
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HECTOR SLAM, odometry in a low cost differential drive robot

I'm a noob in robotics trying to evaluate requirements for a low cost differential drive indoor robot. Would highly appreciate comments on the following questions. Given the inaccuracies in the wheel ...
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45 views

process has died , exit code -11

I installed this framework and followed the instructions, but when I run it, I get the following error: ros melodic ubuntu 18.04 ...
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64 views

How to compute the Hessian matrix in the robustified Gauss-Newton method for optimization

When robustifying the Gauss-Newton method used to find a local minima of a squared error function expressed by: $$f(\mathbf{x})=\frac{1}{2}\Delta\mathbf{z}(\mathbf{x})^T\Delta\mathbf{z}(\mathbf{x})$$, ...
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Using Google Cartographer library standalone

I am working on a project that requires the analysis of the results of different SLAM libraries with respect their accuracy on building a map. Right now, I am more interested in the development with ...
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Some doubts regarding SLAM and its technical terms

I have some questions regarding SLAM and some general technical terms used in the context of it. Q1) **Online SLAM vs Offline SLAM**. Can "Online" SLAM be also called "real-time" SLAM? What is the ...
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60 views

Calculate information matrix for graph slam

0 I am new to SLAM. I am working on graph slam where I need to do pose graph optimisation. For this requirement information matrix is required between two edges for which the transformation has ...
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26 views

How to calculate extrinsic calibration of a non-overlapping multicamera rig?

thanks for taking the time to check my question. Firstly, let me describe the current configuration, I am using 4 cameras that produce non-overlapping images and the goal is to calculate their ...
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Covariance of Gaussian after sequence of homogeneous transformations

Assume we have a robot that moves and observes landmarks on his path. The path is composed of $k$ poses $s_1 \: ... s_k$ where $s_i = [x,\ y,\ \theta]$. From the sensors, we read the motion ...
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Vulnerability of LiDAR systems for autonomous drones

I will soon be working on an autonomous drone project and we're planning to use LIDAR systems for localization & mapping. However, at the same time, we are looking into how to make drones safer ...
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difference between particle filter in slam and normal particle filter

I would like to ask you about what is the difference between particle filter when we use it in Slam methods and when we use it normally to correct our sensor measurement. I mean, is there any ...
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Cheap global shutter cameras with external synchronization

Please recommend cameras for multi-camera setup satisfying the following conditions: Relatively cheap (up to 100$ per camera). Global shutter. No filters on lenses or pixels. Resolution of 1 MP or ...
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Calculate transform from different poses

My robot is at a starting pose $s_0 = (x_0, y_0, \theta_0)$ and, while moving, I receive a sequence of motion measurements $[\mu_1, \mu_2, \: ... \: \mu_n]$, where $\mu_i = (\Delta x_i, \Delta y_i, \...
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Scale factor of Monocular SLAM (Simultaneous Localization and Mapping )

I am using ORB-SLAM3 with a monocular camera on a drone for Augmented Reality application. I need to know the absolute scale of the map formed by the SLAM. I cannot use a stereo or RBG-D setup. Tthe ...
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Relative scale problem

I am doing Monocular Visual Odometry, and I have problem with relative scale. Most of the time its value is between 0.8-1.1, but sometimes it goes crazy and it has value 3,4 and once it had value 25. ...
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What's the difference between optimizing a pose graph only once as opposed to optimizing a pose graph whenever loop closures are found?

I am trying to optimize a pose-graph generated through visual odometry with loop closure constraints. I wanted to know if there are any particular situations where optimizing the graph only once is ...
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Pose-Graph Optimization in MATLAB does not give expected results

I am trying to optimize a pose graph I created in MATLAB using either the optimizePoses(viewSet)-function on the imageViewSet that I have or the ...
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316 views

Frozen map + 'Message filter dropping' - Issues with mapping and navigation in ROS2 Foxy

sorry for the long post, just want to make sure i include all the details. I am working on learning ROS2 by building a robot which maps and navigates my apartment. I'm using the RPLidar A1 sensor ...
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Ground Truth Visual SLAM Data Set

Can you please point me to a data set that can be used to validate monocular visual SLAM? My vision for what this data set looks like is a series of frames, with ground truth pose, ground truth pixel ...
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What's the difference between factor graph optimization and bundle adjustment?

I see that in SLAM literatures, factor graph optimization is frequently used. While in Structure from Motion literatures, usually they use bundle adjustment. What's the difference between the two ...
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How to detect loop closures in 2D laser SLAM?

I am trying to build an occupancy grid map using odometry and 2D lidar data through graph optimization. I am not aware of any reliable loop closing methods using only the 2D laser scans. I have been ...
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Use 2 Cameras as 1 Stereo Camera

I have one Picamera and one normal USB Webcam and would like to use them together as one stereo camera. Is this even possible as the 2 cameras aren't exactly the same? I would like to use them in ROS ...
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Drone lost traj recovery

So I am using slam algorithm to localize the drone which is gps denied . The input to the slam algo is imu data and a video . Now after the first run of the slam algorithm it creates the trajectory ...
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How to calculate the ground truth of your own simple dataset for testing your SLAM Algorithm?

I have tested my SLAM algorithm on EuRoC, TUM and KITTI Datasets. But I would like to test on my own custom dataset. Moreover, I already rectify how to make my own dataset in TUM dataset format, but I ...
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Cartographer: What determines how many nodes are added to a trajectory?

I'm testing cartographer using the Deutsches Museum public bag. I'm trying different Lua settings and checking how it affects the mapping process, etc. What I notice is that, no matter what ...
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No difference between UKF and EKF for SLAM

I built EKF and UKF SLAM algorithms. The problem is that I expected to see a difference because of the more precise approximation of the system in the UKF. Here's a screenshot from the estimated path ...
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How are landmarks updated with respect to each other in SLAM?

One thing I don't understand in EKF SLAM is how landmarks interact with each other. From my understanding this interaction only happens during a loop closing event. When a loop closing occurs, how do ...
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UKF - sigma point creation - Mirroring the chol matrices

maybe this is a stupid question but i came across a problem with my ukf implementation. I use chol() in matlab for my sigma point creation instead of the normal square root of my covariance matrix. Do ...
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Doubt regarding a slam parameter in research paper

I was reading about the SLAM problem in a research paper, Multi-robot Simultaneous Localization and Mapping using Particle Filters by Andrew Howard. What does '$m$' mean here? The SLAM problem for a ...
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SLAM - Angle calculation failure ?-EKF

i am currently building up a EKF SLAM. I dont know where my mistake is but i think it has something to do with the angle my robot is driving towards but im not completly sure. First i thought it could ...
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SLAM Initialize new landmark - specifically the covariance

Im trying to bring an EKF - SLAM to life but it keeps on failing. Specifially, I think, my mistake lies in the initialization of the new cone <-> covariance. I multiply the Jacobian (derived ...
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EKF Update Step measurement data doesnt fit state vector

I have an EKF SLAM Algorithm which tries to estimate the robots position (X,Y,Theta) + the X,Y coordinates of several landmarks. Like in the posted algorithm i have a range/bearing sensor. I ...
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What is the difference between a Bayes Net and a Factor Graph

I am just getting started on understanding Factor Graphs, by going through the excellent guide Factor Graph For Robot Perception by Dallaert and Kaess While I am familiar with the SLAM problem, and ...
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What is the Point of Monocular SLAM

I am not a V-SLAM expert yet, but as far as I understand with monocular V-SLAM there is a scale ambiguity introduced by the fact that a camera essentially is an azimuth sensor that maps the 3D world ...
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Is Lidar SLAM with only lidar sensor and no loop closure detection just a odometry?

I'm a newbee to SLAM. I have a question that in Lidar SLAM(including 2D lidar and 3D lidar), if I only use a single lidar without any other sensors like IMU and no loop closure in the mapping process, ...
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Sparcification of SLAM with SEIF (Sparse Extended Information Filter)

I am studying SLAM (Simultaneous Localization and Mapping) with textbook "probabilistic robotics". I cannot understand well about Sparsification step, so I found original paper for that; ...
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How to evaluate the location accuracy of a visual slam algorithm in an indoor enviorment without motion capture system?

I have a ground mobile robot with wheel for indoor applications and I want to develop a vSLAM algorithm for it. So one problem for me is how to know my modifications do really improve the performance ...
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Compute how well a laser scan matches or overlaps with its environment given a map of the environment and location of the robot is known

If I knew the exact location of my robot and have an accurate map (for eg. an occupancy grid map) of the environment beforehand, how can I compute a measure of how well the laser scan data agree with ...
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EKF SLAM Prediction Step

My question relates to the prediction step in EKF SLAM when we get measurements. This is a question I've encountered while implementing EKF SLAM in ROS. At the beginning of the SLAM loop, we predict ...
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How can we calculate likelihood of sensor values wrt to actual real world?

I am trying to understand Bayes Filter. In its update step we have P(z_t|x_t) as observation model. Slide 37: Bullet 5 of this lecture states "Likelihood of ...
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286 views

Hector_navigaton on ROS Melodic error

I'm a newbie on robotics, and currently, I'm working on a project to make an autonomous robot that can mapping the surrounding environment and decide the shortest route towards the goal while avoiding ...
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112 views

What's the correct approach to merging of localization and odometry data?

We've got a mobile platform with a source of odometry and an IMU, which are merged in an EKF filter (robot_localization node), producing continuous odom->base_link transform. The robot is also ...
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58 views

How to use SLAM generated map to navigate my robot to the destination?

I am trying to understand various SLAM algorithms. In my case, I need my robot to start from point A and reach point B with maximum accuracy as well as precision for all the cases. Note that, as the ...
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Setting An Initial Pose Rotation In ORB SLAM2

I am running ORB SLAM 2 on a drone with a downward facing, RGBD camera. I'm using Gazebo to simulate and Rviz to see the vision_pose ROS topic (the orientation/...
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Do IMU have value in SLAM?

IMU are often used in theoretical models involving SLAM. I'm a bit confused on their practical value since error accumulation is so bad that after a couple seconds you need to completely ignore it. ...
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Which scan matching algorithm can be used to extract the moving objects (in 2D lidar scanner)?

There are different types of scan matching algorithms to match consecutive 2D lidar scans, see https://youtu.be/nvFcN2-NqRc?t=421 (ICP, correlative matching, RANSAC). Most of the algorithms return the ...
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What is the state-of-the-art approach to detect moving objects from mobile robot with 2D Lidar only?

Having a setup of a mobile robot with a 360° 2D lidar (1 plane). What is the current easiest approach to detect moving object with a high reliability from a moving robot? To make it simple, we ...
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How do robots move parallel to a wall/line?

I have been studying robotics by myself, lately. I noticed that there are various mapping, localization methods (popularly under SLAM), but are there concepts relating to the robot moving in a ...
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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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