Wndsn Quadrant Telemeter Tutorials
Making the most out of our graphical telemetry computers.
Like with many complex instruments, there are multiple ways to solve certain problems and to measure the required inputs. Combining the various functions leads to a multitude of advanced uses.
Extending the Scales
Wndsn Quadrant Telemeters measure a maximum of 7° to 12° in angular size. What to do when the object is larger or closer than that? The answer is to extend the measuring scale. How? By adding additional knots on the string.
Prepare your string in a way that there are knots at 1/2 and 1/3 of the length of the string between eye and scale. If you need to measure larger or closer objects, hold the instrument at the 2nd knot and the engraved, e.g. 7° becomes 14° (7 × 2); held at the 3rd knot, the engraved 7° becomes 21° (7 × 3). Note that while one tickmark on the scale at 57.3 cm equals 0.1°, at 57.3 / 2 cm it equals 0.2° and at 57.3 / 3 cm it equals 0.3°.
To subtend and measure angular sizes or distances in the range of ≈ 10° to ≈ 60°, we shorten the string (or move the knot closer to the instrument) even further. As an example, shortening the string to 95 mm (3.76 in) allows us to measure altitude up to 60° with a precision of 0.6° or 36' of latitude (which translates to 36 nautical miles).
Note on the use of the nomogram
When extending the scales, we can't use the Telemeter side for the tan calculation, because the nomogram is calculated and set up for angles up to 7° only and we cannot employ scale jumps here since there is no linear relationship between the tangent of 5° and 50° respectively.