Transcript Mapping (Topographic) Surveys Required: • • • Readings: 17-1 to 17-9. Figures: 17-1 to 17-4,17-6, 17-7,17-10, 1711. Recommended, not required, extra readings: • Hydrographic Surveys section 17-13. Topographic Maps • • • • Topographic surveys,

Mapping (Topographic)
Surveys
Required:
•
•
•
Readings: 17-1 to 17-9.
Figures: 17-1 to 17-4,17-6, 17-7,17-10, 1711.
Recommended, not required, extra readings:
• Hydrographic Surveys section 17-13.
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.
3-D Representation of a topo mapping of site 1, project 1
Methods for Mapping
(Topographic) Surveys
•
Small areas: ground surveys.
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
– 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.
LIDAR Terrain Mapping in
Forests
LIDAR DEM
USGS DEM
LIDAR Canopy Model
WHOA!
(1 m resolution)
Canopy Surface Model
Minus
Terrain Surface Model =
Canopy Height (m)
LIDAR Vegetation Height Model
(LIDAR Canopy minus LIDAR Ground
DEM)
LIDAR data visualization
Click on image
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
Oblique aerial view, courtesy of Washington Dept. of Ecology
Perspective shaded-relief view of 10m DEM,
derived from 1:24,000-scale contours
Perspective view of LIDAR DEM
Interpreted LIDAR DEM. Yellow is landslide, pink is scarp,
green and violet are glacially-scoured surface
Source:
http://pugetsoundlidar.ess.washington.edu/example1.htm
Advanced Total Stations
F
F
Reflectorless or prismless TS up to 2000m on white
surfaces today
Robotic TS “ONE MAN CREW”
High Density (Definition) Survey
(HDS)
(Terrestrial Laser Scanners)
The scanner sends millions of laser pulses to
measure coordinates as it rotates to scan the
features around
All-in-One Total Stations
F
F
More than one technology
The Topcon IS Imaging Station includes:
– Robotic total station
– 3D Scanner
– Imaging system
F
Can perform as a regular or a robotic total
station
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
•
•
•
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
Shaded relief DTM Produced by ArcInfo
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 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
•
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
• 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.
•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
•
•
•
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
•
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
-
-
-
Map the site of project 1, extend it to the edges of
vegetation.
Map every thing that DOES NOT MOVE, 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
point
Horiz. Angle H. Dsitance Remarks
reading
PI (V)
C
T
PC
BVC 2
20
BVC 1
Two vertical
curves can be setout at the same
time from either
BVC 1 or BVC 2.
The direction of
each of the
Centerlines curves
is shown to the
left. Assume that
the BM for
elevation is BVC
and IS NOT 20
Last tree
Yellow-to post
X
X
40’
1
2
3
Contour lines of problem 16-12
5%
Grade
Use of Topography in Selecting a Best Route for a new
Railroad