LiDAR performance
Hovermap ST and Hovermap ST-X use different LiDAR types. The performances of each are described below.
Hovermap ST | Hovermap ST-X | |
|---|---|---|
Number of lasers | 16 | 32 |
Number of laser returns | 2 | 3 |
Laser range | 100m | 300m |
LiDAR field of view | 30° | 40° |
Number of points per second | up to 300,000 (single return mode) | up to 640,000 (single return mode) |
Hovermap field of view | 360° | 360° |
Point density
Point density refers to the number of points in an area. To achieve a quality scan, it is important to understand which areas will receive the greatest point density. While Hovermap does have 360° coverage, it will focus on some areas more than others.
The area of greatest point density is directly in front of the LiDAR sensor (shown as a dark blue cone in the following image). This is because a number of lasers will always be facing this direction, even while the sensor head is rotating.
The rest of the sphere will still have good coverage, but the point cloud in these areas will be less dense. This is because the remainder of the lasers are in constant motion, due to the rotation of the scanning head.
A small blind spot exists behind the body of Hovermap (shown in gray in the following image). This occurs because the body of the Hovermap blocks the field of view in that direction. When scanning, it is important to consider any platform or individual holding the Hovermap.
In practice
The factors above all have implications when using Hovermap. In practice, it can help to visualize the cone of denser points as a flashlight. When scanning, make sure that you focus the cone on any important features that you wish to capture. If you do this, the SLAM process will be able to create a denser, more accurate point cloud, and the possibility of a SLAM slip will be reduced.
Hovermap continuously records point data. Increasing the amount of time spent surveying the target area will increase point density, even when the sensor cannot be directly oriented toward the area of interest.
Tips to improve point density
Move slowly.
Sweep the cone in all directions to ensure a denser point coverage.
When attaching Hovermap to a drone or vehicle, face it so that the cone can see the largest number of features.
Resolution
The closer Hovermap is to its target, the greater the accuracy of the points it produces (beyond the minimum scan distance of 0.5 m). If you are close to your target, you are more likely to produce a clean point cloud the first time, without the need for a lot of cleaning in the postprocessing stage. We recommend that you stay within 40 m of your target.
Captured Data
The data captured by Hovermap includes characteristics such as range, intensity, and the time that the data was captured. Mounting Hovermap onto your platform of choice also allows the system to embed GPS data into the collected LiDAR data. This embedded data can then be used in the post processing stages.