Topographic Surveys and Contours Vocabulary

Vocabulary practice flashcards generated from the Topographic Surveys lecture notes, covering core terms, definitions, relief representation methods, contour types, and survey techniques.

Topography

The configuration, shape, and roughness of the ground, or the field of geoscience and planetary science comprising the study and description of surface shape and features of the Earth and other observable astronomical objects.

Hypsography

A term synonymous with topography that refers to the configuration or shape and roughness of the ground surface.

Etymology of Topography

Derived from the ancient Greek words tóπος (topos, meaning "place") and -ypαφια (-graphia, meaning "writing"), originally referring to writing about a place or local history.

Ordnance Surveys

Detailed military surveys in Britain beginning in the late eighteenth century, used into the 20th century as a generic term for topographic surveys and maps.

Cassini Maps

The earliest scientific surveys in France, named after the family who produced them over four generations.

Topographical Bureau of the Army

The American military office formed during the War of 1812 that conducted early detailed surveys in the United States and became the Corps of Topographical Engineers in 1838.

Spot Heights

Exact land elevation points shown on a map using a dot or triangle accompanied by a numerical value representing altitude above sea level at critical points or features.

Hachures

Short line segment or curve strokes drawn in the aspect direction (steepest slope) where thicker, shorter strokes indicate steeper slopes and thinner, longer, farther apart strokes indicate gentler slopes.

Johann Georg Lehmann

The Austrian topographer who standardized the hachure mode of representing relief in 1799.

Form Lines

Dashed lines on a map that show a general idea of relief without being measured from a datum plane or labeled with representative elevations.

Contour Line (Isohypse)

A line drawn on a map representing an imaginary line of constant elevation on the ground surface.

Layer Tinting

A mapping convention that uses different colors or shades to represent different heights, where darker shades signify greater heights (also called hypsometric tinting or altitude tint).

Hill Shading

A visually striking relief representation method that simulates a light and shadow effect, causing valleys and mountain sides to appear cast in shadow.

Relief Model

A three-dimensional cartographic representation of a part of the Earth's surface that provides an immediate, direct impression of a landscape.

Couloir

A steep gorge or gully formed on a mountain side, represented on topographic maps by "U" or "V" shaped contour lines pointing toward higher elevation.

Arête

A narrow ridge formed by glacial erosion, represented on topographic maps by contour lines whose closed ends point toward lower elevation.

Spur

A lateral ridge projecting from a mountain or main ridge crest, usually formed by two parallel streams eroding gullies down the face of the mountain.

Subaqueous Contours

Depth curves used to portray underwater ground relief, numbered as water depths grow deeper and referenced to a low water datum rather than mean sea level.

Index Contours

Heavier lines drawn at regular intervals (usually every fifth contour line) carrying the elevation designation, typically twice the line weight of standard contours.

Intermediate Contours

The four lighter-weight contour lines located between consecutive index contours on a map.

Feathering

The cartographic practice of omitting intermediate contour lines for short distances where slopes are so steep that the lines would otherwise merge into a single line.

Supplemental Contours

Dashed or dotted lines used to show small elevation changes in areas with minimal terrain relief, typically representing half the standard contour interval.

Depression Contours

Closed contour lines representing low spots or excavations, distinguished by short hachure ticks drawn perpendicular to the line on the downhill side.

Approximate Contours

Contour lines drawn based on educated guesses to represent relative elevation in areas that are ground-inaccessible or obscured on aerial photos by heavy cloud or shadows.

Contour Interval

The constant vertical distance maintained between two adjacent contour lines on a topographic map.

Grade Rod

The specific rod reading calculated by subtracting the required contour elevation from the height of the instrument when performing chasing contours in the field.

Controlling Point Method

An indirect contouring method suitable for large areas and small scales where rod shots are taken at critical slope changes (breaklines) and intermediate elevations are interpolated.

Grid Method

A field survey method where a small area is divided into regular squares using stakes at corners to determine elevations with a level and interpolate contour line positions.

Photogrammetry

The mapping method of plotting topography from measurements taken on aerial photographs using stereoscopic plotters.

Analytical Method (Contour Interpolation)

A mathematical method for finding exact contour locations between two points based on similar triangles using the formula $\frac{d_e}{DE} = \frac{h_m}{H}$.