Navigation Plotting Tools

There are just a few basic tools needed for navigation, yet there are many, many options available — not to mention the unlimited number of gizmos and gadgets that do this or that job in special circumstances.

The basics are a pair of dividers, parallel rulers, a simple ruler, and a protractor. Beyond that we venture into the realm of luxury, which is never far from the realm of clutter.

Below are a few notes on the basic tools. You can click the small pictures for more details on the individual tools.

Dividers are used to measure the distance between two points, and also to help align parallel rulers or plotters. There are several styles. We carry only the one we recommend which is a type of "speed bow" called the ultra light dividers. They are imported from Denmark.

A "bow" is a tool that will hold its point separation once set, and it is set by a rotating knob in the center of the tool — as opposed to conventional dividers which are just pulled open or squeezed closed. A "speed" bow is one that you can pull open or close by hand without having to use the center knob. In other words, you can override the fine control of the center knob by firmly pulling or pushing on the legs themselves.

This particular model has become the dividers of choice for the vast majority of professional navigators worldwide because of its ease of use and accuracy. This was also helped by the fact that it was imported by Weems and Plath which have a worldwide distribution network in nav tools and it sells for a very good price. Before this model appeared some fifteen years ago, quality speed bows were in the 30-dollar range and were awkward to use. This one is light weight, and easy to use.

Parallel Rulers
This is a tool that lets you draw one line parallel to another, some distance away from it. To use it, align one edge of the rulers with the base line, and then holding down that side of the tool, move the other side to the location of the new line. If the new location cannot be reached in one step, then you "walk" the rulers across the page to the destination.

It takes a bit of practice to manipulate these without slipping, but after some practice it is quite easy. There are numerous styles and sizes of these. We recommend clear plastic, 15 inches long.

An alternative to parallel rulers is a rolling tool called a parallel plotter, or more specifically, the Weems parallel plotter, named after its inventor. These are designed to roll without sliding, which they generally do fairly well, with little practice. Unfortunately, rolling plotters do not work well near the edges of charts, or over folds in the chart. We carry both tools underway and use the Weems plotter whenever possible, but immediately switch to parallel rulers if need be.

Ruler and protractor
Navigation plotting is much like any graphical or drafting work. We often need a ruler and, whenever angles are involved — frequently in navigation, for courses, bearings, and vector plotting — we need a protractor. A protractor is a tool that lets us draw angles of a specific size, or draw a line in a given direction.  The square protractor we offer is especially convenient for plotting celestial lines of position, and having the full 360° often reduces the chances of plotting errors if we are very tired underway.

The 4" x 15" ruler we offer can be used with either the parallel plotter or the parallel rules to extend a line, or it can be used as a stand alone device to do the job of both parallel plotter and protractor. Some mariners prefer this one-tool solution to plotting, others are willing to carry an extra tool to expedite individual tasks. With the the "Navigator's Tool Pack" you can practice with each of these tools to see which meets your needs best.

Parallel rulers and plotter are, of course, rulers in their own right, but we have enough need for longer lines and other special applications to justify having a separate ruler in the nav station. Same with the protractor.

What tools are needed for specific courses?
Generally we would say that if you are going navigating, you will need all of these. You could choose only one method of drawing parallel lines (rulers or plotter), rather than both as suggested here, but other than that choice, each of the other tools serve an imporant role in some aspect of navigation plotting. Note that this, however, covers all types of navigation: coastal, celestial, weather work, and radar work. No other tools are needed.

For those starting from scratch on tool selection, we offer the "Navigator's tool pack" as a way to order all with one item, with an additional 15% savings.



Video illustrated article on

using plotting tool usage



Navigator's Tool Pack

Navigator's Tool Pack

Remember the above is a full set for all types of navigation and various other related plotting likely to take place in the nav station. The bare minimum tools required for navigation underway and for doing our home study courses would be simply the parallel rulers ($12.95) and the dividers ($19.95), or a total of $32.90.

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