Topic: 8 Topographic Surveys And Mapping

Question 0

Contour Interval

Answer 0

The vertical distances between contour line.

Question 1

Contour Line

Answer 1

Is the line connecting all points of same elevation.

Question 2

Index Contour

Answer 2

The fifth contour line which is numbered and it has heavier line thickness.

Question 3

Planimetric

Answer 3

2D (x,y) views of natural and cultural features.

Question 4

Topographic

Answer 4

The shape, configuration, roughness, or 3D quality of the earth’s surface including Planimetric features.

Question 5

Map Scale

Answer 5

The ratio of length of an object or feature on a map to the true length.
1:1200 means one inch on the on is 1200 inches on the ground.

Question 6

Plotting Contours

Answer 6

Contours are manually plotted by scaling between two adjacent plotted points of known elevation assuming that a uniform slope exists between these points.

Question 7

Automated contouring systems: digital elevation model(DEM)

Answer 7

3D arrays of points providing a digital representation of an area. Alternatively, the term Digital terrain model (DTM) is used.

Question 8

Automated Contouring Systems: Triangular irregular network (TIN)

Answer 8

• triangle sides must have constant slopes.
• surface area of any triangle is a plane.
• the identification of controlling features (break lines) must be provided to depict contours accurately. Streams, lake shores, roads, railroads, ditches, ridgelines, etc. are examples of controlling features or break lines. Curved break lines such as streams must have enough data points.

Question 9

Contour lines characteristics

Answer 9

• close spacing indicates steep (relatively) slopes.
• every 5th contour line is labeled with the elevation.
• contours don’t pass through buildings
• contours are straight parallel lines passing over built areas
• contours deflect uphill at valley lines - downhill at ridge lines.
• ground slope between contours is uniform.
• contours tend to be parallel on uniform slopes.

Question 10

Completing a map

Answer 10

Map should include: title, scale, legend, meridian arrow.

Title box includes: title of map, name of client, location, name of project, date, scale, name of person who drew map, name of surveyor.

Question 11

Topographic field surveys

Answer 11

Methods for obtaining topography: plane table, transit-Stadia, total station, photogrammetric

Selection depends on terrain condition.

Most common are total station, photogrammetric