# Tag Info

Accepted

### AprilTag vs Aruco markers

Aruco (as implemented in OpenCV) pros Easy to set up (with readily available aruco marker generator, opencv & ros implementation, etc.) fewer false detection (with default parameters) cons ...
• 251

### Which is the best visual fiducial marker (2D barcode)?

AprilTag is the state-of-the-art solution for pose estimation. The library itself already has pre-built functions to compute the marker position, given its size. The pose is estimated by homography ...
• 161

### What's the difference between Pose Measurement and Position Measurement?

what you are looking for is written in the paper. Position refers only to x,y,z translational measurements while pose means position and orientation.
• 477
Accepted

### State of a Robot

To extends the answer from the_parzival a bit: There are different kind of robots so that 'robot state' can have different meanings. If you have a drone or Roomba-robot, the most important state is ...
• 1,335
Accepted

### How do I go about implementing a Kalman Filter for a pose estimation algorithm?

It sounds like you're using the camera frames to get a PnP solution, or something along those lines. A linear Kalman filter will usually work OK for most purposes if you're using roll/pitch/yaw and ...
• 872
Accepted

### Integrating GPS into Graph SLAM (how orientation fixed?)

You can use a very low information matrix value at the orientation elements of your state, given that the information matrix is the inverse of the covariance matrix. The covariance matrix ...

### Choosing the state vector for an EKF

In general, I try to obey the following two rules when selecting states: Only use the states necessary for control, and Choose states to be measurable properties, whenever possible. For example, on ...
• 14.6k

### What's the difference between the term "pose estimation" and "visual odometry"?

It is also often the case that the author lacks knowledge, makes mistakes, or is adding unnecessary statements to their work. Just because it is published does not make it true. In this case though, ...
• 4,205
Accepted

### Position vs Image based visual servoing?

The problem in both cases is to move the robot tool to some pose relative to an object. Let's assume the camera is attached to the end of a robot arm (eye in hand case) so we will consider this a ...
• 1,522

### smoothing the robot poses inbetween two known poses

To get a smooth trajectory you should not have jumps in acceleration and because you are talking about pose both rotational and translational accelerations should be smooth. You can achieve this with ...
• 191

### smoothing the robot poses inbetween two known poses

You could try to use a bezier curve (https://en.wikipedia.org/wiki/B%C3%A9zier_curve) to interpolate with a curve and via points between A and B'. Also, is this a mobile robot or a robot arm? Do you ...
• 477

### What's the difference between the term "pose estimation" and "visual odometry"?

Pose estimation means determining position and orientation. Odometry is using a (any) sensor to determine how much distance has been traversed, so visual odometry is just clarification that the ...
• 14.6k
Accepted

### Number of diagonal elements in the pose covariance matrix

The quaternion part [q_x, q_y, q_z, q_w] has four numbers but is a representation of 3D orientation, which has 3 degrees of freedom. Another common representation ...
• 340
Accepted

### Open source implementations of EKF for 6D pose esimation

I believe this should tick all your boxes: http://wiki.ros.org/robot_localization It's a ROS node for 6D pose estimation that has the following features: Fusion of an arbitrary number of sensors. ...
• 532

### What's a good pose estimation method for high precision (<5mm per-axis) solutions at short range (<50cm)?

The accuracy of fiducial markers (i.e. glyphs) depends on your camera's resolution, noise ratio, focus, and field of view. Essentially, you will need to ensure that there are enough pixels in the ...
• 10.8k

### Full 3D Pose (Scale, Rotation and Translation) Estimation using Gyro and Acceleromter sensors fusion

The packages you've found don't estimate scale or 3d pose because that's not really feasible using just an imu. The only way to get 3d pose from an imu is to integrate acceleration (adjusting for ...
• 2,679

### How many AR markers should I use to get the object pose?

Without knowing exactly what type of AR marker you are interested in, I'll talk about two types that I am familiar with: ArUco and April Tags. Both are AR markers that have open source libraries with ...
• 340
Accepted

### How to properly initialize every new pose in a Visual SLAM algorithm (namely DSO)?

DSO initializes the scene and camera poses with a specific scale factor such that the average inverse depth of the pointHessians is one. After the initialization the first two frameHessians are led ...
• 36

### How to detect writing on a chalkboard?

Since you are going to have a mechanism that can draw within a square why not put a light sensor on it and use the same mechanism scan for the opponent's move? At the start of the game, scan all the ...
• 705

### Resources for object detection with 2D Laser Scanner (planar only)

I think you can divide your problem into two subproblems: 1) Partition your 2D scan into segments/clusters which represent single objects. A basic algorithm could be: Start at first laser reading ...

### How can I calibrate 3 cameras without knowing global pose of the object & camera locations? How can I find the pose of each camera wrt the first one?

The process you need to go through is actually similar to the camera calibration procedure in OpenCV or other software. The chessboard is replaced by your robot, and you can skip the intrinsic ...
• 1,561
Accepted

### Calculate transform from different poses

I am just going to explain from the basics. So feel free to skip through the first part and scroll to the bottom if you want the answer. Basics: The 3 parameters of your pose are $x,y,\theta$. These ...
• 1,561
1 vote

### State of a Robot

The state of the Robot refers to the properties of the robot that you want to estimate. If you take a 2D robot as an example, then you might be interested in its 2d position which refers to  X(t)...
• 148
1 vote

### Is pose estimation using images necessary in visual-inertial SLAM

No, nothing is "necessary". You can estimate the pose of the robot perfectly legitimately using only IMU data. You can also estimate it perfectly legitimately using only image data. But it won't be ...
• 5,142
1 vote

### For pose estimation, what is the typical range of the rotation values that are estimated? Is it from -180 to 180 degrees?

The range between -1 or +1 is a normalized range like you said. The question is the following: Were those values divided by 180 (degrees) or 2*pi (radians)? You should check any existant documentation ...
1 vote

### For pose estimation, what is the typical range of the rotation values that are estimated? Is it from -180 to 180 degrees?

Check whether they are in radians. Most algorithms use radians for pose estimation.
1 vote
Accepted

### smooth robot 3D trajectory using graph optimization

If your problem is small and uncertainty information is not available, you can just set it with identity matrices. Covariance or information matrix will let you set which relative pose to trust more, ...
• 1,365
1 vote
Accepted

### smoothing the robot poses inbetween two known poses

You are right. That is absolutly graph optimization problem. Sorry for the answers above but you don't need spline or acceleration for this. The graph optimization will find 5 poses above in your ...
• 1,365
1 vote
Accepted

### Perspective N point solution: Position drifting linearly with rotation angles?

The problem was a bug in my code where I was accessing the translation part of the solution directly, and not the camera position, so it was indeed a missing transformation. For future reference, the ...
• 1,091
1 vote

### What is the difference between object pose estimation and object tracking?

"Pose" is a commonly used term that means position and orientation, where object tracking would just care about position but not necessarily the orientation. So, for a vehicle on the street, you ...
• 14.6k

Only top scored, non community-wiki answers of a minimum length are eligible