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What is the Caveatron?

An electronic 3D cave survey system

The Caveatron is an easy to use all-in-one cave survey tool and is operated in a manner that builds on conventional cave survey techniques. The basis of a cave survey is the line plot, which is also used by the Caveatron as the skeleton on which the LIDAR point cloud scans are built. Just like conventional surveys, stations are set in the cave and the Caveatron is used to measure the distance, azimuth and inclination between them. All the LIDAR scans are also referenced to these stations. For instance, if you are doing a scan as you move down a passage (a traverse scan), you walk toward a particular station while the Caveatron continually measures its location off of that station. The coordinates of the point cloud for that section are based off the position of that station as determined from the line plot. Since only a single station is used to position each scan, you can make as many different traverses as you want to a particular station to build up a larger area or get additional coverage for areas that may be shadowed in particular positions.

One thing that is a bit different from a conventional survey is the use of a retroreflective card that is held on the station to which you are shooting. This was needed as a way to solve the problem of being sure that you were actually measuring the distance and direction to the station when doing a passage scan with the LIDAR. Since it is impossible to hold the Caveatron perfectly on station while traversing with it, the Caveatron only gets valid position readings when it hits the retroreflective card and all other surfaces are ignored. So, as you move down a passage with the Caveatron, you don’t need to be pointed exactly at the station continuously, just from time to time. The Caveatron does the rest with its built in 9-Degree of Freedom inertial measurement unit (IMU), using the gyroscope and accelerometer to determine the position and orientation of the unit between LRF points. Having the card also helps with the accuracy of station-to-station shots in that it ensures you are actually pointed exactly at the station and not measuring something near or behind it.

The Caveatron has a simple design with a touchscreen user interface, an on/off button, a mini-USB port to recharge the battery and download data, and a neckstrap. Unlike the previous version, the LIDAR module is now fully integrated into the design. The touchscreen and laser rangefinder windows are recessed to minimize the risk of damage and the touchscreen also has an additional screen protector. The enclosure is designed for 3D printing with PETG with seals and O-rings for all opening and a cover over the USB port.  It is designed to be highly water and mud resistant and has been dunk tested and used in a water cave while swimming. 
An internal rechargeable Li-Ion battery powers the system and allows you to operate the system for more than 7 hours of continuous normal use. If this is not enough, the system can be operated while connected to an external USB battery pack. The system runs on a Teensy 3.6 microprocessor at 180 MHz and the touchscreen has a resolution of 480 x 320 pixels. Data is stored to an internal SD card with a capacity of up to 32 GB. A typical cave survey with the Caveatron produces several hundred MB of data. Other features include a built in clock that adds date and time stamps to all survey measurements, a battery gauge, and the ability to upgrade the firmware through the USB port.

© Copyright 2020 Joe Mitchell