Questions? We’re happy to answer them! Contact info@surveydown.com with any questions related to cave diving, cave cartography, survey, exploration, or just diving in general.

1. How are underwater caves mapped?

Cave divers run a continuous guideline throughout the cave as they explore. This line serves two purposes; first, it helps divers find their way back to the surface, and second, it can be surveyed to create a basic map of the cave.

To survey the guideline, divers will use a compass, their depth gauges, and a measuring tape to record the azimuth, inclination, and distance between each point that the guideline makes a change in direction. This data is then entered into cave survey software to produce a simple map of the guidelines called a “stick-map.”

An underwater cave cartographer can then print this guideline map onto waterproof paper, and draw details of the cave passage around the stick-map.

2. How long does it take you to map a cave?

That depends on how big the cave is! By diving two to three times per week in my free time, I can usually map about 10 kilometers / 33,000 feet of cave per year.

3. How long are your cave dives?

My average cartography dive is approximately 200 minutes.

4. Surveying, sketching, mapping, digitizing, etc. a cave seems overwhelming. Is there a way to contribute parts/pieces to other projects instead of owning one from start to finish?

Group cartography projects are possible but require organization, cooperation, and dedication from all team members.

I recommend that each contributing diver does both the survey and sketching for their assigned section of the cave so that they are familiar with the area they will be working in. I also recommended that all of the digitizing be assigned to a single team member for a consistent look on the final map.

5. Why do some maps include the cave-line and others do not? Should I include it in my sketch?

Some cartographers feel that the guidelines should not be included on a map because they are not considered permanent features of the cave. The guidelines may eventually be changed and having old guideline routes on a map can lead to confusion. While this is true, other cartographers may decide that including the guidelines will better help divers understand the cave when used in combination with the map details.

Though it is generally not considered good practice to drastically alter the line routing in a cave, it is a simple job to update a map with the new line routing should the cartographer desire. (Ideally the divers changing the line routing should also survey their new line and send the data to the cartographer).

6. What special equipment do you use to survey and map caves while diving?

Honestly, my survey and cartography equipment is pretty primitive! Aside from my standard cave diving gear, I use a survey slate, waterproof paper, a clipboard, and a mechanical pencil. My survey slate is just a Suunto A-30 compass zip-tied to a small sheet of PVC plastic which I can easily write on underwater. I also have a 50 cm string tied to my survey slate which I use to measure the guideline distances.

7. Do you bring additional lights for sketching?

No, I carry the standard amount of lights for cave diving which is a primary light and two backup lights.

8. What waterproof paper do you use?

I use TerraSlate 5 Mil Copy Paper. Note that a laser printer is required for most waterproof papers.

9. To begin sketching a cave, do you start from the furthest point of penetration and sketch towards the exit, or do you start from the entrance and work your way in?

I work my way into the cave from the entrance, and I try to complete each section (or sketching page) before continuing onto the next page. I often find more cave passages while mapping which can drastically change the original plan for a map. If I start mapping from the farthest point of the cave, those farthest sections may not be included on the final draft if the overall map layout takes an unexpected change.

10. How are maps verified? What if my sketch is contested or believed to be inaccurate?

There are several accuracy grades such as the UIS Grading System that a cartographer can personally assign to their work. Most grading systems use separate grades for both the survey and plan details of a map. A high grade of accuracy requires extensive survey of a cave and the data can be verified through cave survey software.

Most grading systems for the plan details also require that all significant cave features be measured for any grade claiming to be a higher degree of accuracy than a best-guess estimate.

So, a map with estimated dimensions should not be expected to be highly accurate, and a map rated to be highly accurate will have the data to prove it.

11. Is there a list of cave features that are “musts” versus “nice-to-have?”

Drawing the walls, columns, entrances, and general floor contour of a cave will give you the basic foundation for an underwater cave map. Additional “nice-to-have” features include ceiling drops, pits, chimneys, boulders, sediment types, and speleothems such as stalagmites or flowstone, etc.

12. I don’t own an MNemo, can I still survey?

Yes! All you need to survey underwater is a compass, depth gauge, a 2 ft string, and something to write on.

13. Where can I purchase an MNemo survey device?

The MNemo can be purchased online through the Ariane's Line website.

14. I’m good at sketching but I’m bad with computers/software, etc. Is there someone who can digitize my sketches for me?

Yes, outsourcing the drafting process is quite common and many underwater cave maps were not digitized by the cartographer. Anyone familiar with a vector graphics editor such as Adobe Illustrator will be able to digitize your maps. (Digital Artists, Graphics designers, etc)

15. How are the passage widths measured?

Passage widths can be measured using a tape measure, a handheld sonar such as the Vexilar LPS-1, running additional guidelines for survey, or estimating.

16. How is the floor-to-ceiling measured?

Floor-to-ceiling heights are most easily measured using a depth gauge to record the floor depth and ceiling depth, then subtracting the ceiling depth from the floor depth. You can also use a handheld sonar device such as the Vexilar LPS-1 in very large caves when swimming up or down to record depths is impractical.

17. Can you use photos or video to sketch instead of hovering in the caves? What are the pros-cons of that?

Yes, through a process called photogrammetry. Photogrammetry is the science of extracting 3D information from numerous overlapping photos of a specific object or space, such as a cave. These photos are then processed using photogrammetry software to create 2D or 3D models.

It is possible to achieve extremely high levels of detail with this technique, however, it is currently not practical to map large cave systems using photogrammetry due to the many thousands of photos that would be required – not to mention the computer processing power needed to develop the models!

Photogrammetry is currently used to map specific sections of a cave, such as those with archaeological significance so that the targeted features can be studied by scientists who are not certified cave divers.

18. Do you use a legend of cave features while sketching or should they be memorized before sketching?

It is recommended that cartographers memorize their symbol sets to efficiently draw underwater.

19. If diving with a buddy, what can the other team member do while the other is sketching? Should they sketch too? Provide light? Collect other data?

A teammate's primary role is to act as a support diver for the cartographer who is doing a complex task in a challenging environment.

Team members can also assist with laying the primary reel and numerous jump spools required to map a complex cave, removing or adding cartography lines as needed, and providing additional light. Remember: A continuous guideline to the surface must be maintained at all times, and a cartographer does not get to swim around large passages without a line, just because they are mapping!

20. When learning a new dive skill, it’s typically practiced on land before performing the skill in the water. Are there ‘land drills’ one can practice before sketching underwater?

Yes! Mapping dry caves are the obvious first choice for “land drills,” but in the absence of having access to any dry caves, you can map your house, backyard, garage, alleys, streets, parks, anything really... Practice running line on the surface, survey it, enter the data, print the survey, and sketch the location. It sounds stupid but it helps!

The MNemo records inclination so it will accurately survey on land, but feel free to estimate inclination (or depth) data for the sake of practice if you are doing land survey using the traditional compass and slate method.

21. Does Survey Down offer a Cave Survey or Cartography course?

Survey Down will be working in conjunction with Under The Jungle to teach underwater cave survey and cartography workshops to certified cave divers. Contact us at info@surveydown.com for more information.