## The Science behind Wndsn Telemeters

Kamal, nomography, and slide rules.

Inspired by the medieval Kamal, a celestial navigation tool that greatly facilitated latitude sailing, as well as nomography, an almost lost art and science invented in the late 19th century to provide engineers with fast graphical calculations of complicated formulas, and adding an important slide rule principle, the Wndsn Telemeter combines all three techniques in an easy to use and handy distance measuring device.

## 3. Slide Rules

In addition to the principle of the Kamal and those of nomography, the Wndsn Telemeters borrow the treatment of the decimal point from the concept of slide rule calculation.

The slide rule was invented around 1620-1630, shortly after John Napier's publication of the concept of the logarithm. In 1620, Edmund Gunter of Oxford developed a calculating device with a single logarithmic scale; with additional measuring tools it could be used to multiply and divide. In c. 1622, William Oughtred of Cambridge combined two handheld Gunter rules to make a device that is recognizably the modern slide rule.

Pickett N600-ES slide rule. This five-inch 'eye saver' yellow aluminum linear slide rule has a nylon indicator and is held together with stamped aluminum contoured posts.

In slide rule calculations; the user determines the location of the decimal point in the result, based on mental estimation. A slide rule requires the user to separately compute the order of magnitude of the answer in order to position the decimal point in the results. Scientific notation is used to track the decimal point in more formal calculations. (Wikipedia)

Scientific notation is a way of expressing numbers that are too big or too small to be conveniently written in decimal form. Hence, a result of e.g. 5 on the nomograph may translate to 5, or 50, or 500 units measured (5×100, 5×101, 5×102), making the device useful to calculate arbitrary distances.

### Wndsn String Theory

Wndsn string theory posits that the more perpendicular (or obtuse) the string is to the center scale, the more accurate are the results. Which means that you can switch to a different unit (or power of 10) for increased readability.

Wndsn string theory; left acute, right (more) obtuse angle. The 0.3 degrees (left) becomes 3 degrees (right) and hence the result on the D scale moves from 'somewhere between 300 and 400' to a more precise '38' (x 10).