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Mapping (Topographic) Surveys. Required:. Readings: 16-1 to 16-9.1 &16-9.5 Figures: 16-1 to 16-4. Recommended, not required, extra readings: Hydrographic Surveys section 16-12. Topographic Maps. Topographic surveys, why? Planimetric vs hypsometric maps.

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required
Required:
  • Readings: 16-1 to 16-9.1 &16-9.5
  • Figures: 16-1 to 16-4.
  • Recommended, not required, extra readings:
    • Hydrographic Surveys section 16-12.
topographic maps
Topographic Maps
  • Topographic surveys, why?
  • Planimetric vs hypsometric maps.
  • A combination of Planimetric and hypsometric maps is a topographic map.
  • DEMs and three dimensional perspective models.
methods for mapping topographic surveys
Methods for Mapping (Topographic) Surveys
  • Small areas: ground surveys.
slide8

Large areas:

    • -photogrammetry and Remote Sensing, automatic. With ground survey for control, GPS?
    • Overlapped images from a plane, geometry is solved, images are oriented , and finally 3D models are produced and digitized to produce maps.
large areas lidar
Large areas:LIDAR
  • Terrain mapping using scanning airborne laser radar (LIDAR): the aircraft is simply transformed into the equivalent of an airborne total station by combining laser range-finder technology with GPS and inertia systems
  • Knowing the aircraft position (GPS) and orientation, the distance to the ground point, and the angular orientation of the laser beam, the position of a point on the earth’s surface can be found.
  • Several footprints of laser are available to perform various tasks. For example, large footprints VS small footprints in forested and bare-ground areas.
slide13

LIDAR Canopy Model

(1 m resolution)

WHOA!

slide14

Canopy Surface Model

Minus

Terrain Surface Model =

lidar data visualization17
LIDAR Data Visualization

Click on image

Raw LIDAR point cloud, Capitol Forest, WA

LIDAR points colored by orthophotograph

FUSION visualization software developed for point cloud display & measurement

slide21

Perspective shaded-relief view of 10m DEM,

derived from 1:24,000-scale contours

slide23

Interpreted LIDAR DEM. Yellow is landslide, pink is scarp,

green and violet are glacially-scoured surface

Source: http://pugetsoundlidar.ess.washington.edu/example1.htm

control for topographic surveys
Control for Topographic Surveys
  • Horizontal: traversing, triangulation, GPS, extended with photogrammetry in large areas.
  • Vertical: leveling loops, GPS.
  • Control points are the framework upon which the topographic details are usually built. Must be:
    • Within the allowable misclosure.
    • Checked and adjusted.
contour lines
Contour Lines
  • Lines connecting points of equal elevations, such as a shoreline of a lake.
  • Contour Interval: the vertical distance between level surfaces forming the contours. 1, 2, 5 ft
  • Contour intervals depend on map scale and the diversity of relief in the area.
  • Every fifth contour is drawn
  • with a heavier line, elevations
  • are in breaks in the contour
  • lines.
  • Next slide then figure 16-2
characteristics of contours
Characteristics of Contours
  • Must close on themselves, on or off the map
  • Perpendicular to the direction of max. Slope
  • Slope between them is assumed uniform
  • The distance between them indicates the steepness of the slope, gentle or steep
  • Irregular signify rough, smooth signify gradual slopes
characteristics of contours30
Characteristics of Contours
  • Concentric closed contours: hills or depression
  • They do not cross each other, only in special cases
  • They do not cross buildings
  • They cross horizontal man made surfaces in parallel lines
locating contours
Locating Contours
  • Direct method: locate the points of certain elevation. Keep a certain rod reading from horizontal line of site, trace and locate points on contour line.
  • Indirect method: measure the elevation and location of “controlling points”. Interpolate to locate contours. Interpolate at each side of controlling features separately.
  • Slide 16-4.
automated contouring systems
Automated Contouring Systems
  • DTM (DEM): digital elevation (terrain) models.
    • Array of points with measured X, Y, and Z.
    • Grid method: borrow pit, computer interpolation.
    • Irregular method: indirect method, with additional information to produce triangulated irregular network.
    • Assuming the triangle sides are of constant slopes, interpolate along the sides.
slide34

Breaklines:

    • linear Topographic features which have uniform slopes.
    • Must be triangle sides.
    • For example: notice how roads are shown in the TIN and in the contours.
field methods for locating topographic details
Field Methods for Locating Topographic Details
  • Radiation by total station: measure angle and distance to each feature. X, Y, Z of the surveyed point can be displayed in real time.
  • Grid method: suitable

for contours.

  • GPS:

Must maintain satellite

Visibility. Will not

work efficiently

close to building or

Under trees.

accuracy specifications for topographic surveys
Accuracy Specifications for Topographic Surveys
  • More than one standards:national map accuracy standards (NMAS), ASPRS, American Society of Civil Engineers (ASCE)
  • Maximum permitted errors are related to map scale. The smaller the scale the bigger the allowed error.
  • Example: not more than 10% of tested points shall be in error in horizontal position by more than 1/30 inch, what about a map 1 in: 100 ft
project 2
Project 2
  • Map the site of project 1, extend it to the edges of vegetation.
  • Map every thing that DOES NOT MOVES, big or small.
  • Use known control stations and coordinate. Keep good sketches.
  • Contours: interpolated from project 1 earthwork grid, extend it to the limits by hand.
  • Check out: TS, battery “check the charge before you leave, tripod, prism or two, prism pole or two, tape measure, Radios
  • TOB: TS on point 36, first point in table is 20, must give reference azimuth
slide39

X

X

Contour lines of problem 16-12