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.

72 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
3
votes
1answer
28 views

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 ...
3
votes
0answers
85 views

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 ...
3
votes
2answers
138 views

EKF SLAM : Missing older landmarks in new observation

I am a beginner to SLAM and robotics in general and I have been trying to implement SLAM on my GoPiGo3 robot car kit using primarily Chapter 10 from Probabilistic Robotics by Sebastian Thrun as ...
3
votes
1answer
159 views

SEIF ,online version of Graph slam create doubt in Motion Update state

I have a thesis work about Graph Slam The GraphSLAM Algorithm with Applications to Large-Scale Mapping of Urban Structures I try to implement it with the help of this paper but during the ...
3
votes
2answers
300 views

What is appearance-based SLAM?

To my understanding appearance-based SLAM uses only information coming from sensors for mapping and localization. It completely discards control information from actuators. I'm I correct?
3
votes
0answers
328 views

Triangulation from calibrated stereo rig

I am using a stereo rig to do SLAM, calibrated using the MATLAB Calibration Tool. I need to compute the 2D coordinates of a landmark using the observation model obtained from triangulation (the images ...
2
votes
1answer
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: $$f(\mathbf{x})=\frac{1}{2}\Delta\mathbf{z}(\mathbf{x})^T\Delta\mathbf{z}(\mathbf{x})$$, ...
2
votes
0answers
36 views

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 ...
2
votes
0answers
105 views

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 ...
2
votes
0answers
31 views

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 ...
2
votes
0answers
72 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 ...
2
votes
0answers
366 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 ...
2
votes
0answers
104 views

Monocular SLAM depth reconstruction

I am trying to derive the inverse depth equation used in monocular SLAM algorithms. Specifically the equation 8 of the ORB SLAM paper I am very close, except I do not understand where the (u_j-c) ...
2
votes
0answers
254 views

Visual SLAM for wheeled robot

I would appreciate your help for choosing the appropriate real-time SLAM algorithm. I am interested in having autonomous robot, thus a SLAM component is needed for autonomous navigation. The ...
2
votes
0answers
121 views

Need help in implementing EKF based SLAM

I just started learning about slam and I have been trying to simulate a robot moving around a set of landmarks for the past 3 days. The landmarks have known correspondences. My problem is, if I add ...
2
votes
1answer
161 views

Camera pose to world coordinate transformation

I have managed to receive camera_pose for ORB-SLAM by following their code. If I run $ echo /world /camera_pose I receive something like this: ...
1
vote
1answer
50 views

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 ...
1
vote
1answer
81 views

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 ...
1
vote
0answers
34 views

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 ...
1
vote
1answer
55 views

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 ...
1
vote
0answers
24 views

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/...
1
vote
1answer
52 views

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 ...
1
vote
0answers
42 views

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 ...
1
vote
1answer
79 views

Effect of platform speed (how fast it is moving) on the quality of SLAM

I want to know how big of on an impact does the speed of the platform on which your sensors are mounted have on the quality of the outcome of a SLAM solution. Are there are any methods that are better ...
1
vote
0answers
114 views

Sensor model and Inverse sensor model using occupancy grid mapping with lidar for particle filter

I'm a bit confused about how one goes about calculating the sensor model $p(z_t|x_t, m) $ and inverse sensor model for position $p(x_t |z_t,m_{t-1})$. From this answer, it seems like one way for ...
1
vote
0answers
216 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 ...
1
vote
0answers
77 views

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 ...
1
vote
1answer
243 views

Position Estimates from sensor fusion

I have a quadcopter, and several components in play. First, I have a real position system (VICON), and I also have a SLAM platform. Then, of course, the IMU on the quadcoptor. I am trying to ...
1
vote
0answers
100 views

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. ...
1
vote
0answers
31 views

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 ...
1
vote
0answers
97 views

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} \...
1
vote
0answers
666 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 ...
1
vote
0answers
62 views

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. ...
1
vote
1answer
340 views

Camera ego-motion estimation via dense optical flow

Help me please resolve some questions in the article 1) "A Robust Method for Computing Vehicle Ego-motion", Gideon P. Stein et al. According to this paper we can find three components of motion (...
1
vote
0answers
114 views

Camera calibration sequence with ground truth data

I'm looking for a SLAM dataset (monocular or stereo) specifically with a checkerboard, meaning the camera always has a checkerboard in frame. Most popular datasets provide calibration sequences, ...
1
vote
0answers
183 views

EKF based SLAM, marginalization and key-frames

I have a couple of tightly related questions regarding EKF-based visual SLAM. It is common in the Kalman based VSLAM litterature to marginalize 3d points and past poses. Condsidering the EKF as a ...
1
vote
0answers
141 views

Kalman filter localisation equations

I am doing mobile robot localisation as a project. Now I stuck in obtaining the equations of EKF localisation. My robot moves straight for 10 seconds parallel to x-axis and robot equipped with 2 ...
1
vote
0answers
199 views

Scaling monocular SLAM with another source?

I have implemented a stable monocular slam tracking system, based on ORBSLAM2. I am trying to find a way to add real-world distance/scale to this. At the same time, I am running a (less stable) ...
1
vote
0answers
566 views

Calculate input parameters of CTRV model

I am using Constant Turn Rate and Veloctity (CTRV) model to predict the position of the vehicle.The CTRV model assumes a circular path between two consecutive time steps of the car as depicted in the ...
1
vote
0answers
593 views

SLAM - odometry motion model

I am making a project with a 4 wheeled differential robot to make visual SLAM using a stereo rig. I have some encoders to measure de displacement and the steering angle of the robot and I want to use ...
0
votes
0answers
14 views

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 ...
0
votes
0answers
21 views

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 ...
0
votes
0answers
47 views

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 ...
0
votes
1answer
59 views

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. ...
0
votes
0answers
16 views

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 ...
0
votes
0answers
69 views

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 ...
0
votes
1answer
46 views

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 ...
0
votes
0answers
27 views

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 ...
0
votes
0answers
29 views

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 ...
0
votes
0answers
20 views

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 ...