chapter 10 digital mapping and earthwork - u of s … 316 ch 10...digital mapping and earthwork...
TRANSCRIPT
348
March 2012
CE 316
Digital Mapping and Earthwork
CHAPTER 10
www.terrainmap.com/rm22.html
349
10.1 Introduction
350
With a single photograph, X,Y data can be extracted after the photo has
been rectified.
10.2.1 Rectified Photograph
If this tilt can be eliminated, a rectified image, which is essentially a
map, is the result.
.
Where f is the camera’s focal length
AB and DE are equal distances apart
Vertical
Photo
f
H
Tilted
Photo
E D
10.2 Single Images
351
scaled replica of a terrain that has been photographed from two or
more points of view so that the resulting image can be viewed in 3D.
Each photo has 6 degrees of freedom, position and rotation along the
X, Y, and Z axis. These 12 elements are recovered with the orientation.
Interior orientation. Accomplished by the proper placement of the film in
the projector.
Relative orientation, where the stereomodel is established at an
unknown scale. The two projections are aligned relative to each other
using ground points that appear on both images. This fixes 5 of the
elements of one of the pictures (all but the distance the projectors are
apart.
10.3 Stereomodel
352
10.3.1 Digital Elevation Maps
Surface terrain is represented as a network of points of known X, Y, and
Z coordinates.
These are created by digitizing a rectified image, and using a series of
known control points to find the absolute coordinates of points on the DEM.
10.3 Stereomodel
353
10.3.2 Orthophotography
10.3 Stereomodel
354
contours: a line of constant elevation on the ground surface.
Triangulated Irregular Network (TIN): Uses a DTM to create a view of the
terrain.
10.4 Contours and Contour Lines
Computer generated
contours
Triangulated irregular
network (TIN)
Hachures
355 Digital Elevation Map: example
10.4 Contours and Contour Lines
356
Digital Elevation Map: example 2
10.4 Contours and Contour Lines
357
10.4.1 Topographic Map Construction
Project Specifications.
Accuracy
contents of map
Aerial Cameras
Specially designed precise equipment
Photo Control Survey
Ground control is a link between photos and the earth’s surface
Aerial Photography
must be done on a clear day
2D information can be obtained by 1 photo
Overlapping photos are needed to extract 3D information
standard overlap is 60%, 80% for orthophotos
10.4 Contours and Contour Lines
358
Analytical Aerotriangulation
position of control points are measured
with this information, the position and orientation of each
camera when the picture was taken, can be found.
After this, the ground coordinates of any point can be computed
Stereo Data Capture
Stereoplotters allow the user to view the photo in 3D and to input
the X,Y, and Z points into the computer.
Planimetric data: feartures such as buildings, roads, rivers, etc.
Topographic data: breaklines, profiles, etc.
Product Generation
processing digital data into a useful product
planimetric map overlayed on an orthophoto
TIN
10.4.1 Topographic Map Construction
10.4 Contours and Contour Lines
359 Example: Mount Washington
Placement of ground control points
10.4.1 Topographic Map Construction
10.4 Contours and Contour Lines
360
10.4.2 Sample GPS Data
Station ID: 3029 Session #: 274-0 Feb 11, 19116 06:28
Reference Position - NOT SPECIFIED:
Lat. = 0:00'00.000" N Long.= 0:00'00.000" W Height = 0.0 [meters]
Antenna height = 0.0000 [meters] (entered in the field in meters
Receiver serial # = 20103029
Antenna serial # = 20103029 (entered in the office)
NP Software = 2.50 SP Software = 0.11 Download Software = 3.11.01
Survey schedule: UNSPECIFIED
Data-logging start time = 17:44
Data-logging stop time = 22:02
SV Selection mode = AUTOMATIC
Elevation mask = 15 [degrees] Minimum # of SVs = 4
Survey sync rate = 15.0 [sec]
3D Position Best PDOP Position [ 1.8] Mean Position [15430]
Latitude: 49:46'20.04903" N 49:46'21.83974" N
Longitude: 125:17'55.75241" W 125:17'55.95814" W
Height [m]: 1214.9 1193.8
2D Position Position not available
10.4 Contours and Contour Lines
361
10.4 Contours and Contour Lines
362
10.4 Contours and Contour Lines
363
10.4 Contours and Contour Lines
364
Planimetric map overlayed on an orthophoto of Mt Washington
10.4 Contours and Contour Lines
365 Topographic map of area
10.4 Contours and Contour Lines
366 Selected Cross Section
10.4 Contours and Contour Lines
367
10.4 Contours and Contour Lines
368
Example at the Lanigan Mine The Slurry wall centerline was surveyed twice, first using the Mine’s
datum which was tied into a bench mark in 1967. The second survey was
tied into another benchmark near the mine in the summer of 1999. The
two elevations differed as shown in the graph below.
Slurry Wall Centerline Elevations
526527528529530531532533
0+70
0CL
0+90
0CL
1+10
0CL
1+30
0CL
1+50
0CL
1+70
0CL
Station
Ele
vati
on
(m
)
Atlis Datum
Mine Datum
10.4 Contours and Contour Lines
369
Surveying on a construction site is used to:
establish a system of markers in plan and
elevation from which measurement of earthwork
and structures can be taken
making measurements necessary to verify the
location of existing construction and to determine the
volume of work preformed.
10.5 Construction Survey
370
10.5.1 Placement of Slope Stakes
By method of slope distance
A sighting is taken at A where AB equals the instrument height
10.5 Construction Survey
371
The difference in elevation between point A and D is
V = I • sin a
The distance between the points is:
D = I • cos a
d(calc) = w/2 + s(c +/- V) or w/2 + s(f +/- V)
where:
• (c + V) is used for an uphill sight
• (c - V) is used for a downhill sight
• c is the cut at the centerline
• f is the fill at the centerline
When the calculated value of d equals the d obtained by field
measurements, the correct position for slope stakes has been found.
10.5.1 Placement of Slope Stakes
10.5 Construction Survey
372
BY END AREAS
Where:A1 and A2 are the
end areas
Error in this formula is
usually insignificant in
comparison to the volume of
earthwork.
10.5.2 Cut and Fill Volumes
10.5 Construction Survey
373
BY PRISMOIDAL FORMULA
6
AA4ALV 2m1
Where Am is the area of the section
midway between A1 and A2
This formula can be used if more precise values are needed.
10.5.2 Cut and Fill Volumes
10.5 Construction Survey