GPS and RTK-GPS: A Comparison

Global Positioning System (GPS) is a global satellite navigation system. The GPS system was created by the United Statement Department of Defense. It was established in 1973 to produce a better navigation system that would replace previous navigation systems.

Normal satellite receivers compare a signal sent from the satellite to the internally generated copy of the same signal. The receiver must delay the signal in order for the two to match up. The delay is the time for the signal to receive the signal and can be used to determine the distance from the satellite.

The accuracy of the measurement is based on the ability of the receiver’s electronics accurately compare the two signals. Generally, receivers are able to align the signals to around 1% of one bit. This translates to a receiver being accurate to within 0.01 microseconds since the GPS system sends a bit every 0.98 microseconds. In terms of distance, this is accurate to 3 meters. However, other effects introduce errors and the accuracy of an uncorrected signal is around 15 meters.

Real time kinematic (RTK) is based on the use of carrier phase measurements of GPS signal where a single reference station provides the real-time corrections. This allows for up to centimeter accuracy. RTK can also be used with the Russian GLONASS, Chinese Compass, or the European Union’s Galileo. Carrier-Phase Enhancement or CPGPS is another common name for RTK GPS.

RTK systems use a single base station along with a mobile unit. The base station re-broadcasts the phase of the carrier that it measured. The mobile unit compares their own phase measurements with the one received from the base station. This allows the units to calculate their relative position to millimeter accuracy. However, the absolute accuracy is only as accurate as the position of the base station. Typically, this allows for accuracies of 1 centimeter horizontally and 2 centimeters vertically.

Since a base station connection is required for precision, RTK is has limited usefulness for general navigation. However, it is perfect for surveying. The base station is located at a known surveyed location. The mobile unit which is connected to the base station can then produce an accurate map by taking measurements relative to that point.

Rapid static GPS is one of the most accurate GPS techniques. A minimum of two GPS receivers are required. One receiver always remains on the control station while the other is moved progressively from one point to the next. A session is conducted for each point, but the times are significantly shorter than for static surveys. Raw GPS data is recorded continuously and the post-processed later using GPS data processing software.

How Are Visual SLAM and LiDAR Used in Robotic Navigation?

The navigation system is one of the primary components of all types of robotic applications. The primary role of this system is to help robots and other autonomous devices sense and map the surroundings to move here and there in an efficient manner. In most cases, these devices make use of a motion sensor and a software program for the creation of a map. In this article, we are going to talk about how LiDAR and Visual SLAM are used in robotic navigation. Read on.

SLAM is short for simultaneous localization and mapping. The role of the system is to determine the position and orientation of a robot through the creation of a map of the environment. At the same time, the system tracks the location of the map in the environment. Most of the systems depend on optical sensors, such as LiDAR and Visual SLAM.

What is Visual SLAM?

These systems make use of a camera, which works with an IMU. This combo is known as Visual-Inertial Odometry. The term odometry involves the use of motion sensor data in order to get a better estimation after changing the positions of a robot with the passage of time. SLAM navigation is done both indoors or outdoors,

In most visual SLAM systems, the tracking of set points is done using successive camera frames. The idea is to triangulate the 3D position, which is also known as feature point triangulation. Moreover, this information is sent back in order to generate a 3D map and spot the location of the autonomous device.

Apart from this, an IMU is installed to accelerate the feature point tracking. This is even more important with special devices, such as flight based robots and drones. Once the localization and mapping through SLAM are complete, it is easier for the robot to get a navigation path.

What is LiDAR?

This type of system makes use of a laser sensor in conjunction with an IMU in order to map a room. This is done just like visual SLAM, but the accuracy is quite high. Actually, LiDAR helps get the measurement of the distance to a certain object, such as a chair leg or wall. This is done by illuminating the object using several transceivers.

Since light travels at an extremely fast speed, precise measure performance is required for accurate tracking of the exact distance to the target. This is what makes LiDAR an ideal choice as far as accuracy and speed are concerned.

Opting for the Right Navigation Method

If you are finding it difficult to go for the right navigation system for your application, we suggest that you consider the common challenges in the world of robotics. These devices are used on different types of surfaces and pathways. For instance, a robotic cleaner is used on drugs, tiles, and hardwood. Therefore, precise location-based data is the first requirement. After all, these devices can only be used if they can navigate well in a room where there are a lot of obstacles.

With the help of LiDAR and visual SLAM, it is possible to address these challenges. And the great thing is that it can be done quickly and accurately. The cost is quite low as well. In other words, visual SLAM is quite cost-effective and does not require expensive equipment.

Long story short, this is how LiDAR and Visual SLAM used in the field of robotic navigation.

Driving With Satellite Navigation

When you want to use your satellite navigation to get you to where you want to go have you ever thought of where you should put it while driving around.

One area that people seem to put the satellite navigation is at the top of their windscreen right in the centre, have you thought how dangerous that could be as you are limiting where you can see, if you put it anywhere on your window screen this will at some point distract you as you want to know where to go along the road.

People are unaware of where it should go legally as a lot of people think and do not read where it should go.

While driving the correct position for your satellite navigation is in the bottom right-hand corner of your windscreen, in this area you have a lot more vision of the road ahead.

Just think if you were to put it somewhere else how would this reduce your vision and would you be able to see, can you see from all angles for any hazards that could come your way.

So what would be the best place for your satellite navigation device? For me, the best place is not to have one but to plan your journey before hand. Look at the good old-fashioned map book plan a route that you will be taking but also plan other routes for any traffic problems or if you get lost on the route you are doing. If you think you are lost pull over in a safe place and look at your faithful map.

Things that have happened in the past with just relying on your satellite can be very bad, from following a satellite and not looking at your surroundings then driving your car into a lake. This person was not looking through the windscreen he was looking at the device which told him there was no lake. But this lake was made only 3 months ago and the satellite programmers had no idea it was there when the did the last update.

So please remember that the satellite navigation can not see an up to the minute view of the road ahead. You must always look through your windscreen while driving along the road as that is a way you will always see what is in front of you. If you are unsure about how to use the satellite navigation then plan your route before and do not use one.