Beware: You should never explore wild caves alone or without proper gear. Consider getting in touch with a Grotto of the National Speleological Society at www.caves.org or a qualified cave club. These groups are skilled and will train you. Without sufficient knowledge, preparation, and equipment, cave exploring can lead to serious injury or death.
While caving is often just a fun weekend activity for the adventurous types, there are many who do this for a living. If your dream is to be a professional caver or perhaps a scientist that studies caves, you may need to learn how to perform a cave survey. People do this for numerous reasons, as new caves are discovered and old caves change shape.
For example, consider climate change. Caves often contain stalagmites, stalactites, and other speleothems that grow over thousands of years. These formations contain isotopic and other chemical signatures that can be of value. A cave survey helps to uncover these things and allow surveyors to record past climate conditions, such as temperature and precipitation.
Among the most potent greenhouse gases is methane, which has been the research subject for possible cave storage places. There is also a lot of water that can be found in underwater caverns, which could potentially supply cities.
Finally, there’s even cultural reasons. Many caves have religious importance or are linked to myths and legends fundamental to the identities of specific ethnic groups and nations; historians may study caves for these reasons and others.
In this article, we’re going to cover everything about cave surveying: techniques, technology, challenges, and more. Let’s begin!
What Exactly is Cave Surveying?
First, how do we define cave surveying? A cave survey is essentially a venture in which the surveyor aims to produce a reliable map of a cave system. While there may be other motivations for studying a particular cave, a survey is essentially about mapping.
Imagine you are giving someone directions to a new location. This requires two pieces of information: distance and direction. With cave surveying, the concept is the same.
You decide where you begin (A), and where you want to go (B). You calculate the distance from A to B and the direction you need to go to get there. However, there’s almost always a depth factor to consider as well. The inclination angle is also measured to provide the vertical distance between points A and B.
When taking measurements during cave mapping, cavers always double-check their work by going both ways, moving to point A to point B and back again. A simple map of a cave can be made by recording the distance, bearing, and angle of each point inside. The more challenging it is to traverse the cave, the longer this process might take.
What a Cave Survey Team Looks Like
A team of cave surveyors typically consists of three people. They work together to measure and sketch the cave to produce a reliable map.
There are three main roles here: point, instrument, and sketch.
The point person is in charge of locating the ideal places to establish the team’s survey station. This simply means the area that they will work on next. The pointer will mark these stations, and often provide targets for the instrument person to use for measurements. The pointer is the one that moves around the most, and is also the one that is making the first steps in any new territory.
The instrument person’s job is to read out measurements to the sketcher, often using a laser to retrieve these measurements. They may also estimate distances and take photographs, or make other recordings when necessary.
Finally, the sketcher. This is maybe the hardest job, but also the most important. The sketcher jots down all kinds of data, makes drawings or plots, even controls the pace of the survey. After all, the team cannot move forward to a new station until everything has been properly recorded. The sketcher’s job is less physically straining, but the most mentally taxing, by far.
When a new cave is discovered, it’s considered good practice to survey it while exploring it the first time. This way, the ones who found it can get recognition for being first.
Techniques for Conducting Surveys in Caves
Getting Ready for a Cavern Exploration
First, it’s essential to get a few things in order. Whomever the group chooses to communicate with on the surface must know when and where they intend to emerge. The surveying equipment must be double-checked and safely packed before leaving.
Tools such as a camera, notebooks, a compass, a clinometer, a laser distance meter, and a measuring tape are also included.
You’ll take photocopies of the group’s route and destination maps into the cave. Depending on the length of the stay, cooking and sleeping supplies might be brought as well.
How to Find Your Way Around a Cave
During cave mapping, the crew has to cover a lot of ground to reach the survey site. The “flagged” route is usually marked with plastic surveyor’s tape to indicate the best path.
A few pieces of tape are placed on rocks at strategic points along the path. To indicate turns, the flagging tape is bent into an “L” form. Each tape has a pointed end to indicate the shortest route out of the cave.
The cave’s major passages are the only ones that have been marked. Since leaving a highlighted route is an integral part of every survey mission, this is an inevitable reality. The cave maps help the squad get from one marked path to another and ultimately reach their goal.
Cave channel walls and cave features like pits, ledges, and massive rocks are all mapped out for you. Before venturing into uncharted regions, expedition members conduct surveys of key corridors and establish new survey stations to use as landmarks on the return journey.
Tracking Down Potential Leads
Leads, or uncharted passageways, are marked on cave maps. Occasionally, a team will enter a lead only to find that it stops short of its goal.
A lead may extend for some distance and produce more leads. The team conducts a survey as the leads dry up or it’s time to head back to the surface.
To incorporate these findings into the cave map, the crew begins their survey at the closest current station and surveys into the lead.
Several locations inside the cave system serve as survey stations. Stations are identified by names that are a combination of letters and digits. While establishing a new station, one survey crew member must ensure a direct line of sight to the existing station. The group then uses a laser distance meter to calculate the gap between the two posts.
As one person moves to the new station, another stays behind to check the compass and clinometer. The reader aligns the light with the instrument’s numbers for a precise readout. The compass bearing, sometimes called azimuth, is displayed in degrees from 0 to 360. With a clinometer, you can find the inclination (or vertical angle) between the two stations, which can be read in degrees from -90 to +90.
The sketcher tracks all the survey information (distances, compass bearings, and vertical angles) in a notebook. At each stop, the sketcher also notes the passageway’s estimated dimensions. The height, width, depth, and lateral distances to adjacent walls of the station’s passageways are given. The information is written on the survey book’s left-hand pages. The survey photos are drawn as lines on the gridded sheet on the right.
In a different volume, cave structures, swamps, and geological and biological phenomena are cataloged in great detail. Every item located in close proximity to a specific station is cataloged in the inventory book under that station’s entry.
Final Steps of Cave Mapping
As the team exits the cave, they input the survey data into cave mapping software. Once all of the survey lines in a cave have been measured, the software will report the total length of the cave as measured by the survey.
The program creates a “line map” of the cave, which displays the paths taken by the survey lines as they link up the various survey stations. The tunnel walls and features are drawn by hand around the computer-generated line plot using the drawing made in the cave. To complete the “master map” of the cave, these updated maps are linked together.
The computer also records information about stock on hand. With this data, we can create maps of the cave that show us exactly where the water is. In addition, we know exactly where every other exciting feature is located for future visits.
What Data is Collected While Mapping a Cave?
Measurements of the cave’s size, slope, and elevation and observations of the cave’s geological formations, hydrology, and biological communities are all examples of the kinds of data generally acquired throughout the mapping process.
See the image below for some of the typical symbols used to identify and label different elements encountered in the cave.
Challenges of Cave Mapping
Mapping caves, especially vast, complicated caverns that might stretch for kilometres below, has proven quite difficult for mostly self-explanatory reasons. Sometimes a cave is essential to various parties, and surveying must be done regardless of the difficulty. Mapping caves is crucial for management purposes as well, when it comes to caves that are getting commercialized.
These caves require careful monitoring and protecting the natural environment inside and out, as well as understanding the broader implications of everything that goes into the whole thing.
Speleologists, or those who study caves, face a challenge when attempting to map particularly complex caves. Some of these systems feature large underwater rivers or caverns that might be well hidden behind fallen debris. Sometimes, there are some really narrow openings, which complicate proper surveying, even as current software has become more sophisticated and easier to use.
To actually handle the mapping process, various types of technology are employed.
Cave Mapping Technology
More precise cave maps have been made possible because of recent advances in technology and methodology.
Compass Mapping of Cave systems
One may make a reasonably accurate map of a cave system with a compass, measuring tape/laser range finder, and inclinometer to determine the slope.
Correcting magnetic north and true north when using a compass is always necessary. Caves are constantly evolving due to tectonic or erosional action; therefore, it may be required to update cave maps periodically.
Measuring and Mapping Software for Caves
CaveWhere is an example of existing software capable of automatically creating maps from simple measuring equipment. Cave profiles can be curved and fitted to bigger maps used in specific places using this mapping program. Users can take 2D data and project 3D maps, which is quite useful. The software has a straightforward interface that allows the rapid generation of maps using field data.
Therion, a piece of open-source software released under the GNU General Public License, serves a similar purpose. The program may be rendered in stereo (3D glasses required) or off-screen.
Several other popular navigational aids, such as COMPASS and Walls, can help you compensate for the difference between true and magnetic north by providing declination.
More Complex Cave Mapping Technology
Tomography Based on Electrical Resistance
Geophysical techniques like Electrical Resistivity Tomography (ERT) have recently evolved to aid speleologists in creating more accurate cave maps. This technique involves electrical currents sent through the bedrock or surface. The cave’s voids strongly contrast the solid rock above them, making it easy to tell exactly where pathways converge and diverge.
Pins and wiring can be spaced at different intervals to map caves from the outside using ERT. Speleolgists place a wider gap between pins allowing for a stronger ground signal. Mapping profiles offered by ERT allow for the creation of maps in both 2D and 3D, with the ability to cover great distances.
Mapping Electromagnetic Fields From the Air
Airborne electromagnetic mapping (AEM), another similar technique, has been utilized to map underwater cave networks. A plane or helicopter would be used to broadcast an electromagnetic signal.
Conductivity contrasts in voids allow caves to emerge in the imaging, much like ERT and allow mapping to be accomplished even in challenging caves like submerged ones.
Drone Mapping of Underground Spaces
The next steps for cave mapping may involve AEM or similar electromagnetic techniques using UAVs, which offer a low-cost way to map using this method and may be more suitable for different elevations needed for UAV systems to fly so that the depth of signals can be adjusted as required, but are still not discussed at length in the scientific literature. UUVs, or unmanned underwater vehicles, can be used as a variant in caves below the surface.
With mapping software, we can draw detailed maps easily manipulated and integrated into global atlases.
The true test of cave exploration is locating and filling all the empty spaces. Practical geophysical approaches include ERT and AEM. But, it’s possible that even these methods are overly simplistic or don’t go into sufficient depth.
In addition, complete gaps may go unnoticed if signals fail to penetrate particular locations. Thus, the difficulty will be developing new methods that may increase precision while decreasing the time spent capturing the level of detail required to map caves.
How Long Does It Take to Map a Cave?
How long it takes to map a cave is contingent upon several variables, such as the cave’s size and complexity, the reason for the mapping, the accessibility of resources and technology, and the expertise of the mapping team.
It may only take a few hours or days to map a small cave for recreational purposes, but it may take months or even years to survey, measure, and analyze data from a big, complicated cave system.
Things To Remember when Performing a Cave Survey
There are a few things to keep in mind while surveying, besides standard caving safety rules and etiquette.
First, the instruments are typically not waterproof. Not only are they expensive, but they play a significant role, and it’s important not to neglect them. Take care of them, keep them clean, and always double check that everything works before you set out to the actual cave.