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LIDAR Module

Two types of LIDAR modules for different types of cave passage and different price points.

The Caveatron has interchangeable LIDAR modules to support scanning different sizes of passages and to provide options for the cost of the LIDAR, which is the most expensive component of the system. At the present time, three LIDAR module types are supported – a 4 m, a 12 m, and a 25 m range LIDAR. 

The 4 m LIDAR module is the lowest cost LIDAR and is based on the Neato XV LIDAR scanner. It works well at shorter distances down to about 0.1 m and has a sampling rate of over 1700 points/second. It also has the simpliest interface. This was the LIDAR originally developed for the Caveatron and was used to collect most of the sample data. The 4 m LIDAR is a triangulation-based system design so requires the use of flat windows for its enclosure, resulting in a small occluded area at corner.

The 12 m LIDAR module is based on the RP LIDAR A1M8 and is nearly as low cost as the Neato XV. It also works well at short distances down to about 0.1 m and currently supports a sampling rate of 2000 points/second with the existing Caveatron design but can potentially support up to 8000 points/second in future designs. This LIDAR is a good all-around choice since it provides the densest sampling, has good accuracy at close-range and can work out to reasonable distances. This was the LIDAR can fully replace the functionality of the XV LIDAR and is even slightly smaller. Other variants of the RP LIDAR capable of longer range use the same protocol and support is built into the Caveatron code, however they have not been tested. These LIDARs also requires the use of flat windows as they are triangulation-based, but a custom 3D printed enclosure design has been developed that has an even smaller corner occlution than the XV enclosure.

The 25 m LIDAR module is based on the Scanse SWEEP LIDAR. It is suited for hallway sized passages and larger and has good long range sensitivity out to 25 m. It is also a little smaller and lighter than the other LIDAR modules. However, it has a 1000 points/second sampling rate so provide a lower point cloud density and has measurement error that increases to large values at ranges less than 1 meter, so is not well suited to crawlways or other small passages. It also has a higher power consumption than the 4 m LIDAR, so has about 15-20% less run time. The 25 m LIDAR is a time-of-flight based system so can use a clear dome-style enclosure, providing a full 360º of unobscured scanning.

The LIDAR modules are connected only by two thumb screws and a twist-lock cable connector, so can be quickly and easily changed in the field. That way the LIDARs can be interchanged depending on the type of cave passage to scan. Separate calibrations are performed for each LIDAR module and the system automatically detects the type of LIDAR attached to load the correct calibration parameters. The Caveatron can also be used without any LIDAR module attached allowing it to act as an electronic survey instrument for collecting conventional survey shot data.

© Copyright 2017 Joe Mitchell