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 perform active search in point feature based monoSLAM?

I am modifying an implementation of SLAM with single camera, MonoSLAM [1]. Instead of image patches, I want to use features points (ORB) to track landmarks. MonoSLAM uses a EKF framework. So for ...
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186 views

How to calculate observation matrix Jacobians in EFK based mono slam? What are projection Jacobians?

I have been trying to understand an implementation of monoSLAM 1. But my question is generic to EKF based single camera SLAM. My Jacobian calculation leads to complex and lengthy expressions while ...
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1answer
196 views

Robot moving on a flat floor - 2D or 3D SLAM?

What is the best way to model the SLAM problem (offline) for a wheeled robot moving on a flat floor in 3D space (the pose has only 3 degrees of freedom)? In terms of sensor data, we have the wheel ...
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104 views

How to cope with an optical window limitation on 2D LiDAR?

I have a very small and cheap robot and I wanted to mount a 2D LiDAR on a bottom of it (3cm above the ground). It seems to be great as during the mapping the lidar will detect even small elevations ...
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2answers
666 views

How does fast slam creates grid maps?

I've implemented fast slam using landmark detection and the map stored is a feature map, made of landmarks positions. I would like to create a grid map, and my questions are about how does the robot ...
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3answers
2k views

RGB-D SLAM - Compute Information Matrix

currently im working on a RGB-D SLAM with a Kinect v1 Camera. In the front-end the SLAM estimates the pose with Ransac as an initial guess for the ICP. With the pose estimation i transform the ...
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2answers
73 views

provide world map for ekf global localization problem

I am trying to implement the ekf_localization algorithm in page 217 (Table 7.3) of the probabilistic robotics book by Thrun. From my previous post, I understand that I need to extract observed ...
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132 views

Convert sonar scans to Lidar scan file

Has anyone tried to map environments using Sonars or 1D ToF sensors? Since it's very difficult to implement such an algorithm from the scratch, I'm planning to use an existing ROS packages such as ...
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Why does the low variance resampling algorithm for particle filters work?

I am studying and coding particle filters and I am using the Low variance sampling algorithm suggested in the Probabilistic Robotics book. I understand the procedure for the algorithm. A random number ...
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1answer
240 views

smooth robot 3D trajectory using graph optimization

I want to solve a trajectory smoothing problem using graph optimization. I have asked questions on how to solve this problem in a previous post and got directed towards using graph optimization. I ...
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smoothing the robot poses inbetween two known poses

I have a set of N robot poses between point A and B. I use a global localization technique to estimate poses at point A and B. As a result, I have a new corrected pose B'. Please see the figure below. ...
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Map initialization problem in Mono SLAM

I'm reading and trying to implement the paper Monofusion(V. Pradeep, C. Rhemann, S. Izadi, C. Zach, M. Bleyer and S. Bathiche, "MonoFusion: Real-time 3D reconstruction of small scenes with a single ...
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Fiducials in conjuction with AMCL

I'm having some trouble getting fiducials (using aruco_detect) to work alongside amcl. The goal here is to use normal amcl localization when a fiducial is not present, and to switch to localization ...
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Any reference for “3D feature matching + ICP”?

One of the simple tricks in getting high performance for a global 3D point cloud registration is combining "3D feature matching + ICP". For example FPFH matching + RANSAC for initial pose estimation ...
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71 views

EIF slam algorithm implementation as per Probabilistic Robotics

I want to implement EIF slam from Probabilistic Robotics Table 11.2. This is the algorithm for EIF slam. To construct $\Omega and \xi$ matrix I write down a Java code. Here is my code ...
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How to calculate a covariance of trajectory?

I have a drifted LiDAR odometry $^w \textbf{T}_{1:k}\in SE(3)$ and a drift corrected LiDAR odometry $^w \textbf{T}'_{1:k}\in SE(3)$ by a loop closure where w represents the reference world frame. ...
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955 views

Mobile robot navigation without static map

I am working on an autonomous mobile robot based on ROS. All the tutorials and examples requires a static map which need to be generated in order to do the localization and mapping. Do i need to ...
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1answer
134 views

EKF Slam algorithm doubt at observation update

I have some doubt on EKF Slam with known correspondence in the measurement update state. I follow the algorithm from Probabilistic Robotics by Sebastian THRUN. This Algorithm is on Chapter 10 page No:...
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Lost on SEIF Slam repeated update landmark

I am working on Sparse Extended Information Slam. I take the reference from Probabilistic Robotics, by Dr.Sebastian Thrun (Chapter 12,page 303). I have some doubt about the implementation of the ...
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247 views

GraphSLAM equation doubt

I have question about GraphSLAM implementation. To find out the path and map using GraphSLAM we rely on this equation: $$\mu=\Omega^{-1}\xi$$ where $\Omega$ is our information matrix which ...
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326 views

How can I get the distance from a robot to a beacon?

I'm planning to create a Raspberry Pi robot to map a room. I intend to use a particle filtering algorithm as one of the central points of the project, that will allow me to work out my position ...
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1answer
538 views

Is this SLAM performance typical or am I doing something wrong?

I'm experimenting with SLAM for the first time. I am using ROS on a Turtlebot3, which has a Raspberry Pi and a single Lidar sensor, Robotis LDS-01. I am running a configuration with three computers, ...
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1answer
109 views

Fixing the first node in Graph-based SLAM

The first node in the graph SLAM should be fixed. The famous "a tutorial on graph based slam" paper is showing that we can fix a node by adding identity matrix. Why adding identity to the Hessian of ...
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1answer
146 views

EKF localization data association

I am working with ROS indigo and clearpath huskyA200 and wanted to implement the EKF localization with unknown correspondences with my own hokuyo lidar data for a school project. Giving the algorithm ...
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3answers
301 views

loop closure detection in visual SLAM

A robotic system is moving a getting its current location using visual odometry (incremental estimation of rotation and translation). To correct its localization, a loop closure technique may be added....
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108 views

Relation between GraphSLAM and Iterative closest Point algorithm

I have lots of doubts about GraphSLAM, The GraphSLAM Algorithm with Applications to Large-Scale Mapping of Urban Structures. When I practically implement it I get matrix singularity error. I taken ...
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145 views

Matrix is singular error in GraphSLAM

I have gone through The GraphSLAM Algorithm with Applications to Large-Scale Mapping of Urban Structures. I implemented the code for GraphSLAM. The fundamental formula of GraphSLAM is $$\mu = \Omega^...
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1answer
202 views

Graph Slam Landmark remove and then again add it

I try to implement Graph Slam in real dataset. My data set have some data that describe that the Robot observe same landmark over and over with a large amount of time difference. Prof. Sebastian ...
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59 views

How to detect loop in robot movement observing odometer data

I have some odometer data. This data are based upon robot movement. I can transfer those raw data to a motion equation from where I get x,y,and theta co-ordinate of a Robot. If I plot those x,y ...
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3answers
2k views

Integrating GPS into Graph SLAM (how orientation fixed?)

I'm working on Graph SLAM to estimate robot poses (x, y, z, roll, pitch, yaw). Now I want to integrate GPS measurement (x, y, z, of course no angles). I implemented GPS as pose's prior. But I have a ...
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1answer
434 views

Multiple View Triangulation method used by COLMAP

I'm looking at how COLMAP does multi-view triangulation. I can't work out what this function is doing. I can't find any formulas which look similar. The input "proj_matricies" come from pose data, the ...
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EKF-SLAM Update step, Kalman Gain becomes singular

I'm using an EKF for SLAM and I'm having some problem with the update step. I'm getting a warning that K is singular, rcond evaluates to ...
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2answers
189 views

Why use GraphSLAM?

I am doing some project on Slam. I have a data set of a moving Robot which can give me the value of forward velocity(m/s) and angular velocity(rad/s) and time(s). Now if this data are provided I can ...
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1answer
789 views

Marginalization in Graph SLAM [duplicate]

I have several questions about the process of marginalization in SLAM algorithms: 0 - What are the mathematic intuition behind marginalization process 1 - I know marginalization of states or points ...
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How to update a new pose in iterative pose optimization problem?

There are multiple ways to update new pose in iterative pose optimization problem. The easiest one we often find in papers in robotics is as SO3 + translation Update on right \begin{equation} \...
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1answer
53 views

GraphSlam Matrix Subtraction doubt

I am trying to implement GraphSlam from this paper. I have some doubt regarding the algorithm described in this paper at table2: Algorithm GraphSLAM_linearize. I have a doubt in line 7. As per my ...
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1answer
95 views

Confusion of EKF equations

I read Probabilistic Robotics by Sebastian THRUN (online version). I also read http://ais.informatik.uni-freiburg.de/teaching/ws12/mapping/pdf/slam04-ekf-slam.pdf Question1 : What will be the ...
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1answer
63 views

GraphSlam doubt about variable elimination technique

I am trying to implement Graph Slam. For tutorial purpose I read the paper "The GraphSlam Algorithm with Application to Large-Scale Mapping of Urban Structures" by Sebastian Thrun. At the beginning of ...
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2answers
281 views

Real-time object classification for an indoor autonomous quad-rotor

I am designing an indoor autonomous drone. I am currently writing an object classification program in OpenCV for this purpose. My objects of interests for classification are: ceiling fans; AC units; ...
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585 views

ROS: joint_state_publisher dies when used in remote launch file

I've been trying to run robot_state_publisher and joint_state_publisher on a remote TX1 running Ubuntu 16.04 and ROS Kinetic. When running the node from a local launch file (manually ssh into the ...
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770 views

Using gmapping without ROS?

Is gmapping on OpenSLAM.org still maintained? Or is the maintenance entirely over in ROS ( https://github.com/ros-perception/slam_gmapping/tree/hydro-devel/gmapping ). When trying to compile gmapping ...
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1answer
145 views

sparse matrix in EKF SLAM

I've successfully done with EKF Localization Algorithm with known and unknown correspondences that are stated in "Probabilistic Robotics". The results make perfect sense,so I can estimate the position ...
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1answer
1k views

EKF SLAM and Mahalanobis distance?

So far I have done EKF Localization (known and unknown correspondences) and EKF SLAM for only known correspondences that are stated in Probabilistic Robotics. Now I moved to EKF SLAM with unknown ...
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45 views

EKF based Slam implementation with landmark identification in Global frame

I am working on mobile Robotics. I want to implement Slam. I have a very specific question about EKF Slam. To implement Slam I read the book "Probabilistic Robotics". I read its online version. There ...
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4answers
1k views

Which micro-controler/processor to be used for autonomous stereo vision robot system?

I am very new two robotics, however I have a working stereo algorithm which I want to combine with a SLAM algorithm. I am developing this system for an other application but I decided integrating it ...
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333 views

How does marginalization of variables effect least squares SLAM energy function?

Consider a simple example of Bundle Adjustment where I have robot and landmark poses $x = \left[ x_p \text{ } x_m\right]^T$ and measurements given by $z$, such that a simple factor graph can be ...
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1answer
166 views

Does marginalization increase the number of edges in Graph SLAM?

I thought marginalization does not change the number of the edges but this material (page 11) describes that as a result of marginalization we will have more edges in graph. Why does it increase the ...
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2answers
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Why do we need a marginalization in Bundle Adjustment?

A common practice in Bundle Adjustment is to reduce the state dimension by marginalizing structure or pose states to improve the optimization speed. In case 3d points(structure) $\textbf{p}_i$ are ...
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1answer
808 views

GraphSLAM: why are constraints imposed twice in the information matrix?

I was watching Sebastian Thrun's video course on AI for robotics (freely available on udacity.com). In his final chapter on GraphSLAM, he illustrates how to setup the system of equations for the mean ...
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How to penalize blurred images in Bundle Adjustment?

We know that when rotational and linear velocity of the camera is high it is highly likely to get blurred images. The blurred image affects the quality of the accuracy in the feature tracking problem. ...

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