Introduction
Mapping is one of the many use cases for lidar today. Usually, the sensor is mounted on a UAV, car, or another carrier platform like a robot. In conjunction with GNSS and an IMU, a precise map with accurate position information can be created. In most applications, using an algorithm that combines the data from the three sensors is crucial, because only so a useful 3D point cloud can be generated.
GNSS
Using a normal GNSS sensor is generally not sufficient for lidar applications. Due to local circumstances like atmospheric conditions, radio interference, and other factors, GNSS is only accurate to around five meters. To determine the movement of the lidar sensor as well as 3D orientation and position, higher accuracy is essential.
Real-Time Kinematic (RTK)
Real-Time Kinematic (RTK) enables centimeter-accurate positioning by eliminating local influences. RTK uses two GPS receivers acting as a Base and Rover to get correction data. The Base is set up on a point with known coordinates and calculates the difference between the received GPS position and the actual position. It then sends those coordinates to the Rover so that a centimeter-accurate position can be obtained.
Emlid has developed several high-performance RTK receivers at affordable prices over the past years. Recently, they launched the Emlid Reach RX receiver, which is lighter, smaller, and easier to set up than every other RTK receiver in their line-up. By connecting to your smartphone via Bluetooth, it accesses NTRIP correction data over a network, meaning that a second receiver is not required.
Paired with the small size, the weight of only 250 grams, and the ruggedized case, Reach RX performs to the highest standards in almost any condition. These features are especially useful when lidar is used on a UAV or another carrier platform on the ground.
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