Have you ever wonder when we started connecting points of equal elevation with lines to form what we call contours?  I am digressing a bit from the digital 3D Model issue, but I think it is important to see what our predecessors used to depict land.

In the late 1600 and early 1700, Edmund Halley use contour type lines (isogons) on a chart of magnetic variation.  Halley was an astronomer, and researched comet sightings in 1456, 1531, 1607, and 1682.  He predicted its return in 1758 and when it appeared the comet generally became known as Halley’s Comet.

The Dutch land surveyor, cartographer and weatherman Nicholas Cruquius drew the bed of the river Merwede with lines of equal depth (isobaths) at intervals of 1 fathom (6 feet) in 1727.  This bathymetry map was one of the first of its kind.

A Frenchman by the name of Philippe Buache made a 10 fathom chart of the English Channel in 1737 and published in 1752.  This chart was used by the French army.

It was not until about 1771, that Marcellin du Carla-Boniface began using contours to depict land surface.  A map of France was produced by J. L. Dupain-Triel using 20 meter contour lines, hachure, spot-elevations, and vertical sections.

During this time frame an English mathematician by the name of Charles Hutton began using contour lines to determine volumes of a hill.

In 1807, President Thomas Jefferson establishes the Survey of the Coast and appointed Ferdinand Hasslar, a Swiss surveyor and professor at West Point, and reported to the Secretary of Treasury.  In 1878, Survey of the Coast and Geodetic Survey were combined to form The US Coast and Geodetic Survey.  In 1970, C&GS became the National Ocean Survey and later National Ocean Service with National Geodetic Survey handling the geodetic functions.

The task of building and entire geodetic network across the US had to be a daunting task, especially considering the instruments and theodolites of the day.  A lot of the leveling was trigonometric in the early 1800’s, later to be replaced by “spirit leveling” which was significantly more accurate.

One of the significant products of C&GS was the “Quad” sheet.  These were topographic maps of the US, which included contours.  I used these frequently in my early days of surveying.

With the advent of new digital surveying and mapping capabilities, the accuracy, predictability and clarity of maps has significantly changed.

Once contours became an accepted method of presentation, they were used to depict many other items.  For instance, barometric pressure, temperature, environmental issues, population, etc.

Contour lines drawn on paper were some of the first ways that land relief was shown in a somewhat 3D representation.

Definition:

Contour lines are imaginary lines which represent the intersections that arise from horizontally slicing up landforms into equal vertical intervals like a layer cake (remember seeing physical site plans made from layers of thick paper). They can be defined as lines on the map depicting the metric locations of points on the earth's surface at the same elevation above sea level.  Contour lines are measured up from a base datum, usually sea level and the lines measured down from the datum are called depth contours or isobaths.  Few contour lines exist in nature with the exception of shorelines and a few man made features.

Being able to read a contour map and see 3D relief usually takes a trained eye.   Having grasped this ability, you will be able to see valleys, high spots, ravines, gullies, and flat plains.  It is still important that the contours be labeled so that you can begin telling increase in elevation.  These are very visible in the quad sheet shown above.

So contouring had to begin somewhere, but for us, a contour is a standard feature that we expect to see on construction plans.