No. 250 Waypoint Ruler The Waypoint Ruler has been designed to simplify the process of transferring data from electronic navigation aids to your paper charts. This instrument is ideal for plotting latitude/longitude coordinates from devices such as G.P.S., Loran, Transit and celestial navigation computers. The Waypoint Ruler will also give rapid readings of true courses, bearings and distances. The Ruler does not have to refer to the charts' compass rose and can be used on the lap with badly creased and folded charts. The bi-rola Waypoint Ruler comes with a handle that also serves as a pencil holder, a pencil, instructions and a durable vinyl pouch. Dim.: 5-1/8" x 15-1/4". Wt 5 oz. 

Chart Protractor "The bi-rola Chart Protractor has made my task of teaching navigation Easy!" Captain Laura Tritch


















The bi-rola Chart Protractor turns the tedious task of plotting into child's play. This Chart Protractor virtually eliminates the need for other devices except a pencil. Plotting a course is as simple as laying the protractor along your course line and aligning the compass disk. Laying off courses, bearings, distances and loran interpolation is so easy you can forget about other methods. Corrections can easily be made for variation and deviation. The body of the bi-rola Chart Protractor also has scales for nautical miles, millimeters and loran interpolation. Dimensions: 5-1/8" x 15-1/4". Wt 5 oz. 










P.R. 500 Rolling Plotter Made with the professional in mind, the P.R. 500 has a considerably larger body than the smaller bi-rola rule. Built to take the rigorous use aboard commercial and blue water vessels, the P.R. 500 provides one of the easiest methods invented, to date, of plotting courses. Dimensions: Length 19-5/8", Width 3-5/8", Thickness 1-1/4". Wt: 1 lb. 10 oz.

Features: Patented four-way rolling motion Roller body has protractor markings every 1/2 degree 1-1/4" magnifying lens for enhancing chart data Easy to follow instructions Comes packaged in a protective, durable vinyl pouch.  


Rolling Plotter Our Very Best! The bi-rola rule represents Weems & Plath's efforts to provide the very best plotting tools. Constructed of heavy duty plastic with brass rollers, the bi-rola rule is built to withstand years of trouble free use. The bi-rola rule's patented vertical and horizontal rolling motion simplifies course and plotting calculations, while the unique radial arm allows you to automatically include compass corrections in your course plotting. All together, the bi-rola rule is the most completely self-contained plotting device in its class. Dimensions: Length 13-7/8", Width 2-5/8", Thickness 1". Wt: 12 oz.

Features: Patented four-way rolling motion Roller body has protractor markings and a nautical mile scale Radial arm has Loran interpolator scales and 200 millimeter rule Automatic compass corrections When radial arm and body are used jointly, the bi-rolaŠ rule becomes a 440 mm (17") divider (approximately) A speed/time/distance table is included Easy to follow instructions Comes packaged in a protective, durable vinyl pouch 





Nautical Slide Rule Gives immediate solution to all speed-time-distance problems. Equally applicable for nautical or statute miles. Speed in knots or m.p.h., time in hours, minutes or seconds, distance in nautical or statute miles (or yards if desired and if speed is in knots). Easy to read and accurate. Standard in U.S. Navy. Dimensions: 7-3/8" square. Wt. 5 oz. 



Course & Leg Identifier for Expanding Square Pattern & Sector Pattern Searches Also known as the Search Pattern Slide Rule or Coast Guard Plotter, this tool is a "must have" for active duty Coast Guard, Auxiliarists, or anyone else who might have to run a search pattern. The Course & Leg Identifier quickly calculates the heading and run time for each leg of either an expanding square pattern or sector pattern search, giving you more time to focus on the search. Dimensions: 6"x 9". Wt. 3oz. 113 Course & Leg Identifier


Star Finder 2102-D This star finder graphically portrays the altitude and azimuth of the fifty-seven numbered stars in the Air and Nautical Almanacs. Additional celestial bodies may be plotted on the star base. Special diagrams permit rapid check of hour angle, and also provide means of finding the altitude and azimuth of unplotted bodies or the identification of unplotted bodies from known altitude and azimuth. Diameter: 8.5". Wt. 1 lb. 150 Weems & Plath Star Finder 2102-D



Vectormaster permits rapid solution to problems involving vectors, such as those encountered in current sailing, determination of true wind direction and force, and apparent wind to be expected on other headings. Given the position of a storm, and the direction and speed of its advance, you may quickly determine the course which will put maximum distance between your ship and the oncoming storm. A circular slide rule is located on the reverse for the quick solution of time, speed and distance. Instruction booklet included. Dimensions: 7" square. Wt. 4 oz. 

Celestial Slide Rule The celestial slide rule will significantly reduce the effort and time for determining values used in celestial navigation. This quick and easy device is also a great complement to your navigation computer. The slide rule has GHL (Greenwich Hour Angle), LHA (Hour Angle), t (Meridian Angle), SHA (Sidereal Hour Angle) and observers meridian. When two or more of the values are known, the rest can be determined by a single alignment. Diameter: 7". Wt. 2 oz. 7543 Weems & Plath Celestial Slide Rule


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