This is part one of a five part series called Mapping Caves, where the basic steps to underwater cave cartography are outlined in a way that both divers and non-divers alike will understand.

Introduction

In this series, we will introduce the basic three steps to underwater cave cartography, and conclude with a brief introduction to some alternative techniques that make use of modern technology.

How are the maps drawn?

Divers are often surprised to learn that most flooded cave maps are still drawn by hand underwater. This is because the majority of these maps are drafted to be used as tools to assist cave divers with planning and navigation - they are not intended for accuracy-dependent research.

A cartographer must independently navigate and map kilometers of flooded cave in the most efficient, cost-effective way available to them. For most of us, even in the modern era of technology, that means using a pencil and waterproof paper.

The first rule of cave diving is to always maintain a continuous guideline back to the surface. As divers explore a flooded cave for the first time, they will also survey that guideline to create a stick-map of the cave passages.

By printing this stick-map on waterproof paper, a cartographer can return to the cave and sketch details of the tunnels around the stick-map which represents the guideline they are following.

Cartographers can then scan their sketches for digitization by tracing them in a vector graphics editor such as Adobe Illustrator.

How are the maps used?

Cave divers primarily use maps to determine their navigation to specific sections of the cave, but they do not bring the physical map with them on their dives. So, underwater cave maps are used for planning dives before entering the water.

With this in mind, cave cartographers aim to build a road map of the cave passages that show the general dimensions, depth, and length of the tunnels in a way that is easy for divers to memorize.

These classic, hand-drawn maps are ultimately made to document caves from a "big picture" point-of-view.

How long does it take to map an underwater cave?

The amount of time it takes can vary widely based on the length and conditions of a cave.

Generally speaking, for a map of 10 kilometers in length, a diver will spend approximately 120 hours on survey and exploration, 120 hours sketching underwater, and 180 hours on the computer managing survey data and digitizing the map.

In total, a typical cave map will take 8-12 weeks to complete if treated as a full-time job, with over 6 weeks of work being spent underwater.