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Topographic Surveying

Terms in this set (28)

Topography
The configuration or shape and roughness of the ground.
Topographia
a description of a place
Topographos
describing a place
"Topos" + "Graphia"
-place + description of
Topographic Survey
A process of determining the positions, on the earth's surface, of the natural and man-made features of a given locality and in determining the configuration of the terrain
Topographic Map
A graphical portrayal of topography.
Spot Heights
Indicate the elevations at particular points.
Hachures
Consists of rows of short, nearly parallel lines whose spacing, weight and direction produce an effect similar to shading.
Contour Lines
A line joining points of equal elevation on the map.
Subaqueous Contours
"Depth curves" used to portray the ground underwater.
Ridge and Stream Lining
Used to emphasize the location of high and low ground, usually used as an overlay in aerial photographs and topographic maps.
Form Lines
Resemble contours, but are not drawn with the same degree of accuracy.
Layer Tints
Each elevation zone is indicated by printing a distinctive color or tone between the bounding contours.
Shading
An assumed light source from the northwest is imagined as creating areas of light and shadow in a mountainous area.
Illuminated Contours
The contours are drawn as if they were illuminated by a light source from the upper-left corner of the map.
Block Diagram
A pictorial representation of the surface, drawn from a viewpoint in space.
Relief Model
A representation of the terrain done in 3D to suitable horizontal and vertical scales.
Contour Lines
are the fundamental source of terrain information on such maps.
Contour Intervals
difference in elevation between two adjoining contours.
1. Index
2. Intermediate
3. Supplemental
4. Depression
5. Approximate
Types of Contours:
Index
Defined as every fifth contour (usually) in which the line thickness is made heavier than the rest.
Intermediate
Defined as lighter weight contours found in between index contours.
Supplemental
Used in areas that are so flat that the contours are far apart (to better depict the relief).
Depression
Used to show low spots
Approximate
For areas where the elevations are not accurately determined.
1. accuracy
2. features
3. legibility
4. cost
5. use of the map
Factors Affecting the Choice of Contour Intervals:
1.Elevation Estimation - linear interpolation
2.Reservoir Capacity Estimation - volume
3.Flood-zone Maps - overflows
4.Intervisibility Between Points - profiles
Applications of Contours:
Project Control for Topographic Surveys
The reference framework should consist of two or more permanent control points and/or benchmarks located in the vicinity of the project.
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