# Tag Info

## Hot answers tagged gps

20

Primarily, dead reckoning is used along with some other technique, generally SLAM-like. The robot builds a map, and then tries to localize within that map. For example, using laser range scanners, and based on dead reckoning, the robot has an idea of where it is. By comparing the laser range data to the map, it can improve its estimate. Relevant resources ...

9

I understand you problem is to find different means to GPS to find your position within a given reference frame. This problem in isolation is called localization, and there are many ways to perform that. Firstly you will have to differentiate between relative methods, so measurements which provide a change in position to a previously known position. This ...

8

Can't answer all your questions, but based on your use case Differential-GPS might help you. Modern tractors are using this for precisely navigating on fields (in autonomous mode). Here fixed ground stations are used, which know their exact position and calculate the error in the current signal. This adjustment is then used by the other GPS receiver in the ...

6

A traditional approach is to use an error correcting algorithm like a Kalman filter. By combining dead reckoning from wheel encoders and heading commands with GPS you can smooth out GPS jitter. This is not an instantaneous improvement as it requires a series of measurements to estimate the error inherent in the GPS signal.

6

There is a whole area of literature on this topic. The most general idea is that of Simultaneous Localization and Mapping (SLAM), where the robot must build a map at the same time as it locating itself in that map. Depending on how accurate you want your maps to be, you can attempt a simpler problem of creating an occupancy grid map, which assumes you know ...

6

You might be able to do this using inductive coupling to give the quad copter some indication as to which direction it should move to approach the landing pad. On the landing pad is a single coil on the vertical axis (this is the transmitter). On the quad-copter are two coils, 90º apart and on the horizontal axis (these are the receivers). An alternating ...

6

Google Earth exists for precisely this purpose: overlaying your own data on a map. You simply write scripts to translate (or export) your data into KML format then add the URL to Google Earth like so: With regard to terms of use: the terms of use for Google Earth only forbid you to use the software to control the behavior of your vehicle, not to represent ...

6

Yes. The px4 software for the pixhawk autopilot has an extended kalman filter that uses an accelerometer, a gyroscope, gps, and mag. A paper describing the a smaller ekf which only estimates attitude can be found on archive.org and code for the full ekf can be found on github with further information on archive.org.

5

I'd summarize my read of both of those as: Don't use our logic to provide turn by turn navigation to vehicles Don't use our maps for business asset tracking unless you've signed a commercial use agreement Hard to tell if your use case described violates either of these terms. In any case, check out http://www.openstreetmap.us/.

5

The algorithms are essentially the same regardless of what sensors you are using. The real issue, which Chris touched upon, is that SLAM is hard even with very good sensors. I would consider GPS, wheel odometry, and an IMU to be necessary to even attempt slam with ultrasound. If you are just looking for cheap localization I recommend taking a look at ...

5

A Vicon motion capture system system is used in the TED Talk that you referenced. It is similar to a Kinect in that gives the 3D coordinates of any object being tracked within its field of view. Like the Kinect it uses IR, but uses IR reflective balls attached to the quadrotor and the presenters pointer to identify and track objects. Not to mention it is a ...

5

In my opinion, the main difference is : Positioning : gives information about the robot coordinates. It gives raw data that you can use. Localization : it is the process of the robot (or other actor) locating itself (or the robot) on the map. Here a "method is applied" to locate the robot. Positioning gives you the coordinates. Localization is determining ...

4

I know this is an old question but I will just add a bit to the currently existing answers. First, this is a very complex problem that everyone is trying to tackle, including google with their Tango project. In general, to localise indoor you either need to rely on your internal sensors, or get assistances from a indoor infrastructure deployed to assist you ...

4

I would go with one of two-ish methods to do this, but both methods require the craft to know its own position. You could do this with GPS, or an IMU, or any other means or combination of position tracking. Method 1 - Only track where you are and where "home" is. Use sensors to detect obstacles along your path and navigate around them as applicable. ...

4

Precise vehicle location is not a very useful piece of data in autonomous driving so I would not expect to see many products focusing on it. Path planning and following for cars is a solved problem. If you have a static environment where nothing changes, any good position sensing will let you control a vehicle to follow a path. However, there are very few ...

4

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 represents the uncertainty about the measurement, and the information matrix the certainty about it. So, the GPS constraints would have a small value at the elements ...

4

This is a complete re-working of the answer I had originally provided. If you're curious, you can check the edit history and see what was posted earlier. In comments to this question, OP stated that they might be able to get throttle and steering angles for the robot, but they probably wouldn't be accurate. That's okay; it's better than nothing. OP also ...

3

I work on race cars which occasionally race in built up areas such as street circuits. As part of the mandatory electronic systems we fit a GPS antenna to the car to allow vehicle tracking. Some of the guidance we have for the installation is Fit the antenna to the upper surface of the car Keep the antenna within 5 degrees of horizontal Do not place ...

3

If your goal is to have a georeferenced localization, you will have to use GPS at some point. The other techniques (dead reckoning, SLAM, ...) will only be useful to "bridge" spotty GPS/indoor absolute positioning reception.

3

I actually work as a programmer for the tractors that bit-pirate mentioned. There are several ways mentioned that can get you more accurate results. It depends largely on your application and what you are trying to accomplish. WASS uses a signal to augment not as accurate as some other methods but you will get decent. If your platform is fixed you can just ...

3

As other posters have pointed out, using some form of differential GPS will give you large improvements in precision. We have used the Magelan mb500 commercial platform and it claims an accuracy of around 2-3 cm when in RTK fix mode. However, in areas of bad satellite coverage it would sometimes not even provide a solution at all, where cheap GPS receivers ...

3

There is an error in your posted equation for the Jacobian $F_J$, so that could be the source of the problem. It should look like this: $F_J = \begin{bmatrix} 1 & 0 & -C \sin \theta \\ C \frac{\sin \theta \sin \lambda}{\cos^2 \lambda} & 1 & C \frac{\cos \theta}{\cos \lambda} \\ 0 & 0 & 1 \\ \end{bmatrix}$ With that new Jacobian I ...

3

The NS-HP is a \$50 RTK-capable GPS receiver providing centimeter-level accuracy: NS-HP is a high performance GPS receiver capable of 2 / 4 / 5 / 8 / 10 / 20 / 25 / 40 / 50 Hz update rate. At 1Hz update rate, NS-HP can accept RTCM 3.x message type 1002, 1004, 1005, and 1006, or SkyTraq raw measurement data from a base station to perform carrier phase RTK ...

3

ROS has a package called robot_localization that can be used to fuse IMU and GPS data. This package implements Extended and Unscented Kalman filter algorithms. The package can be found here.

3

No, it is not possible to eliminate the cumulative position error caused by sensor noise and bias without using an additional sensor which can report any kind of position measurement. Even the best sensors and filtering will not be able to eliminate in a closed-loop fashion the position error.

3

Do you have a simulation? I would recommend that you simulate the data first to debug and tune your KF. The simulation should model the true IMU outputs (Grove has some details on that) and true position with error models. Start with truth to make sure the KF estimates zero errors, and then add errors one at a time (bias, SF, Misalignment, noise, etc.) to ...

2

To do SLAM, you will need a relatively good estimate of position. Robots that use laser scanners can make do with just odometry, because the data is relatively accurate, and the scanner data can be used to help localize in subsequent time steps. Ultrasound sensors are very fuzzy, they generally have a direction fuzziness of 20+ degrees, and anything in the ...

2

Optical flow sensors (such as those used in computer mouses) are good for this situation. Most will give output in terms of translation. Alternatively, you can just use a basic camera and run some optical flow algorithms on the data. This will give you the same basic information. It might be easier when doing it this way, to adapt an algorithm that will ...

2

http://www.locatacorp.com/ might be the solution you are looking for. They offer technology to create a local constellation indoor. It emulates the satellites for indoor GPS applications. I believe it can use GPS receivers indoor without the need for additional hardware on the robots.

2

You're asking how to use an acceleration sensor to make better position measurements. As you've correctly pointed out, these accumulate error over time. One way to improve this is to have periodic absolute-position updates, like from GPS, or from the techniques in many of the answers here. However, don't overlook any abilities you may have to get absolute-...

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