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.

Filter by
Sorted by
Tagged with
23
votes
8answers
15k views

Absolute positioning without GPS

Using an IMU a robot can estimate its current position relative to its starting position, but this incurs error over time. GPS is especially useful for providing position information not biased by ...
4
votes
2answers
2k views

the uncertainty of initializing new landmark in EKF-SLAM

In EKF-SLAM (based-feature map) once the robot senses a new landmark, it is augmented to state vector. As a result, the size of the state vector and the covariance matrix are expanded. My question is ...
2
votes
2answers
969 views

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 ...
8
votes
3answers
2k views

SLAM without landmarks?

First, is it possible to build map without landmarks for a robot in 2D? Let's say we have an aisle surrounded by two walls. The robot moves in this environment. Now is it feasible to build such a ...
1
vote
1answer
1k views

How to compute the error function in graph SLAM for 3D poses?

Given a pose $x_i = (t_i, q_i)$ with translation vector $t_i$ and rotation quaternion $q_i$ and a transform between poses $x_i$ and $x_j$ as $z_{ij} = (t_{ij}, q_{ij})$ I want to compute the error ...
4
votes
1answer
837 views

Calculate the uncertainty of a 6-dof pose for graph-based SLAM

This question is strongly related to my other question over here. I am estimating 6-DOF poses $x_{i}$ of a trajectory using a graph-based SLAM approach. The estimation is based on 6-DOF ...
6
votes
1answer
6k views

Are there any advantages to using a LIDAR for SLAM vs a standard RGB camera?

I've been thinking about building a small UAV with an onboard LIDAR, just for fun. I'm interested in SLAM and autonomous flight indoors and thought that I would need a lidar to get a 3D map of the ...
9
votes
3answers
2k views

What algorithm can I use for constructing a map of an explored area using a number of ultrasound sensors?

Ultrasound sensors are incredibly cheap these days which makes them a popular choice for many hobbyist robotic applications, and I'd like to use a bunch of them (say 10) around a robot with an ...
5
votes
1answer
911 views

role of chi2 in SLAM back-end optimization

All-most all SLAM back-end implementation compute chi2 estimates. Chi2 computation is usually used to compute the best-fitness score of model to the data. How it is related to optimization framework ...
2
votes
2answers
480 views

how to plot $\pm 3 \sigma$ of a landmark in EKF-SLAM

I have implemented 2D-SLAM using EKF. The map is based-feature in which there is only one landmark for the sake of simplicity. I've read some papers regarding this matter. They plot the $\pm3\sigma$ ...
0
votes
1answer
86 views

SLAM Scan Matching. Scan vs previous-scan OR scan vs previous-map?

When using Scan Matching ICP for FastSLAM, which is the proper way to use it? Between the current scan and the previous one, or between the current scan and the stored map? Can both be used? If so, ...
0
votes
2answers
134 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^...
9
votes
2answers
1k views

The relationship between point cloud maps and graph maps

I am most familiar with SLAM maps that are point clouds, usually in the form of a vector like $<x,y,\theta,f_{1x},f_{1y},...,f_{nx},f_{ny}>$. I also understand how to create a map like this ...
6
votes
2answers
90 views

How does a self-driving car locate itself when the environment changes?

There's something I don't quite understand about SLAM. When a self-driving car wants to locate itself using a prior map, how does it do that when the environment keeps changing, e.g., new cars parked ...
4
votes
1answer
133 views

How to avoid matrix singularity in GraphSLAM

I am trying to implement GraphSLAM from Sebastian Thrun's paper, The GraphSLAM Algorithm with Applications to Large-Scale Mapping of Urban Structures. When I compute the inverse of my information ...
3
votes
1answer
131 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 ...
2
votes
1answer
142 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 ...
2
votes
1answer
164 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 ...
1
vote
3answers
197 views

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. ...
0
votes
1answer
213 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 ...