Navigation at sea during the Golden Age of Piracy was a complicated endeavor that required diligent and non-stop effort on behalf of those serving as navigators, and sailing from one destination to another was anything but simple.
Pictured here is a reproduction of a 1676 Map of Carolina by cartographer John Speed. You'll note that the coastline looks odd. This is because the orientation is that north is to the right-hand side, with the Outer Banks islands noted in the bottom-right as the map strays into the Virginia territory, while the left hand side stretches to St. Augustine in Spanish-controlled La Florida. This wasn't uncommon in coastal maps, favoring a depiction of the coastline upon the approach rather than dictating north to be the top of the map. In this case, this map depicts the coastline to those arriving to the Carolinas from across the Atlantic. A spyglass assisted greatly in analyzing the distant coastline and comparing geography with maps and charts to help determine the ship's current position.
A compass too would be an invaluable tool, for determining north, with needles able to be re-magnetized by a lodestone. Another piece of the equation is the tool located to the right of the map; a mariner's quadrant. These simple devices were used as far back as the ancient Greek and would soon phase out in favor of the "backstaff" and then later the sextant. You'll note it's wedge based shape, 25% of a full circle, hence it's name. From the pointed central tip there is a plumb line that hangs down to a brass weight, and along it's side are two small wooden blocks with holes drilled. This device could only be used twice per day, at noon, and at midnight, as close as possible to exact times. At noon, the user could line up the two eye-holes and stare directly into the sun, and the angle would cause the line to hang down over the markings and indicate a number of degrees. These numbers indicated your current degrees north or south of the equator for the purposes of establishing your current latitude. However this number would have be adjusted as well after obtaining the reading, as an accompanying book would direct the user how to adjust it based on the current date and season.
One issue that could arise when attempting to use the quadrant is that the user would prefer to be on solid ground to get the most accurate reading, and ships rarely sat still for precise calculations. Going ashore along the coast, or to sandbars, atolls, or rocky islets would provide much better readings. Cloudy days also cause issues. If you miss the ability to stare into the sun at noon, you can try again in twelve hours by instead staring at Polaris, the North Star, at midnight. Again, assuming you can see it.
The type of quadrant pictured here that I have is essentially the equivalent of a DIY Mariner's kit from the 17th century. Being a simple device in all truth, shops at ports would sell prints of the facing with the noted degrees and calculations, and the purchaser would be required to apply it to a cut piece of wood and install their own plumb line with a weight of sorts. Adding eyelets were optional, many instead stared along the flat edge of the board itself. Fancier and more expensive versions of the quadrant would have been made of etched brass, but would have been far less common.
Now that's determining the direction of north, and establishing your latitude. Longitude was much harder to keep track of, and required diligent bookkeeping. To track longitude, one would have to note how much time was spent traveling east to west, at what degree of angle, and recording such information knowing at how many knots the ship was traveling for that duration. Typically this was kept track of on a pegboard called a "Traverse Board" before being recorded in logs.
For navigation, and the purposes of the above, one would also need to know what time it was, hence having an hourglass. Or, multiple as many ships had, as they were prone to break being glass. Sundials, often found with compasses, also played a role here. Tracking time was mandatory for knowing when one could use the quadrant, and was also vital information for recording east-west travel on the traverse board. Hourglasses aboard ships were often designed for increments of 30-minutes, and were required to be flipped as soon as they ran out. This was very important, as every delayed time threw the known time to become askew, which would cause readings to become increasingly askew. Often, hourglasses found aboard ships featured loops on both ends so that they could be hanged from hooks on swaying ships, rather than sit on a desk where they could be knocked off.
Crews would need to measure the knots the ship was traveling, time would have be diligently kept so that quadrant readings could be taken upwards of twice per twenty-four hours, compass readings would help inform degrees of travel for accurate marking on the traverse board, which would time and again be reset after being recorded into a logbook, charts would be analyzed time and again, and would be corroborated by sighting islands and coastlines on the distant horizon. With all this combined, "navigation" was often a multi-person effort. Even if a single sailor thought they could tackle all of the above - they still had to sleep at some point, and during that time the ship would remain in motion, un-recorded otherwise.
Assuming all of the above was completed well, and all cross-referenced appropriately, a crew might have some idea where they are in the world; albeit with an ever-present margin of error. Hats off to those navigators of old who tackled this profession well. Navigators were a mandatory part of most every crew, at least those who didn't want to to simply follow visible coastline. While navigators certainly were aboard most all pirate vessels, one notable one that would be a shame to not mention here is that of John "Bartholomew" Roberts, known posthumously as "Black Bart" Roberts. Initially a sailor under the captaincy of pirate Captain Howell Davis, upon Davis's death in 1719 Roberts was elected as captain by the men for both his personality and abilities as a skilled navigator.