• TABLE OF CONTENTS
HIDE
 Front Cover
 Executive summary
 Introduction
 Data collection
 Data reduction
 Profile comparison
 Conclusion
 Appendix A. Ground truth profiles...














Group Title: UFLCOEL-97012
Title: Comparison of laser swath mapping data with conventional ground truth beach profiles
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Permanent Link: http://ufdc.ufl.edu/UF00091091/00001
 Material Information
Title: Comparison of laser swath mapping data with conventional ground truth beach profiles
Series Title: UFLCOEL-97012
Physical Description: 1 v. (various pagings) : ill., maps ; 28 cm.
Language: English
Creator: Browder, Albert E
University of Florida -- Coastal and Oceanographic Engineering Dept
Publisher: Coastal & Oceanographic Engineering Dept., University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1997
 Subjects
Subject: Cartography -- Laser use in -- Florida -- Florida Panhandle   ( lcsh )
Beaches -- Remote sensing -- Florida -- Florida Panhandle   ( lcsh )
Satellite geodesy -- Florida -- Florida Panhandle   ( lcsh )
Aerial photogrammetry -- Florida -- Florida Panhandle   ( lcsh )
Environmental mapping -- Florida -- Florida Panhandle   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: by Albert E. Browder.
General Note: Cover title.
General Note: "July, 1997."
 Record Information
Bibliographic ID: UF00091091
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 39865254

Table of Contents
    Front Cover
        Front Cover
    Executive summary
        Page i
    Introduction
        Page 1
        Page 2
        Page 3
    Data collection
        Page 4
        Page 5
        Page 6
    Data reduction
        Page 7
        Page 8
    Profile comparison
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
    Conclusion
        Page 17
    Appendix A. Ground truth profiles and uncalibrated laser data profiles
        Page A-1
        Page A-2
        Page A-3
        Page A-4
        Page A-5
        Page A-6
        Page A-7
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Full Text



UFL/COEL-97/012


COMPARISON OF LASER SWATH MAPPING DATA
WITH CONVENTIONAL GROUND TRUTH BEACH
PROFILES




by



Albert E. Browder


July, 1997








Comparison of Laser Swath Mapping Data with
Conventional Ground Truth Beach Profiles

Albert E. Browder
Graduate Research Assistant
Coastal & Oceanographic Engineering Department
University of Florida
Gainesville, FL 32611

EXECUTIVE SUMMARY

This report compares survey data collected using a new airborne laser swath mapping
system with conventional ground surveys taken with level, rod, and tape. Both the laser swath
survey and the conventional ground surveys discussed herein were collected along the Florida
Panhandle in October, 1996. The laser swath mapping was conducted by Optech, Inc., as a
demonstration of the laser system for the Florida Department of Environmental Protection, the
Florida Department of Transportation, and the U.S. Geological Survey. The ground truth surveys
were collected as part of the demonstration and as a part of ongoing field studies of shoreline
recovery from the effects of Hurricane Opal.

The laser swath system uses a laser ranging system mounted in an airplane that flies along
the subject area. The unit includes an oscillating mirror which directs the pulse of the laser and
traces out a "swath" beneath the airplane along the flightpath. This allows the collection of data
along a swath 100-m wide or more in a matter of seconds. The horizontal and vertical position of
the aircraft are determined by a global positioning system (GPS). For the flight discussed herein,
data were collected along the entire shoreline from Bay County to the Florida-Alabama state-line,
involving over 30 million data points along more than 300 kilometers of shoreline in five counties.
The entire data collection process was accomplished on one day in a matter of hours.

The collected data represent horizontal position and vertical elevation at points spaced
roughly 2 meters apart. Once converted to horizontal coordinates (UTM or State Plane Coordinates
for example) and a proper vertical datum (National Geodetic Vertical Datum of 1929), the
topographic laser data were gridded and sliced to produce profile sections corresponding to the
beach profiles surveyed by conventional techniques. The two sets of profiles were then compared
to determine systematic and root-mean -square errors between them.

Comparison of the datasets indicates a systematic error of 1.5 ft (45 cm). This error is
primarily a result of the lack of a field calibration on the day of the flight. It is believed a proper
calibration would remove most of the systematic error. Using the ground truth surveys to
"calibrate" the laser data and remove the systematic error (which appears as an offset), the
calculated RMS error between the laser data profiles and the ground truth profiles of this study
indicate an RMS error of 0.68 ft (20 cm).

Given the accuracy and volume of data collected in such a rapid and relatively inexpensive
manner, laser swath mapping appears to be an excellent means of documenting shoreline changes,
for both position and volume change. Such a system could prove invaluable in assessing storm
damage across a wide area (as in Hurricane Opal) in a short period of time. It is thus
recommended that the laser swath mapping technique be implemented as soon as possible.









Comparison of Laser Swath Mapping Data with
Conventional Ground Truth Beach Profiles

Albert E. Browder
Graduate Research Assistant
Coastal & Oceanographic Engineering Department
University of Florida
Gainesville, FL 32611

July 1997



1.0 INTRODUCTION


This report compares the agreement of survey data collected using a new airborne laser
swath mapping system against conventional ground surveys taken with level, rod, and tape. The
surveys discussed herein were conducted as part of the Florida Department of Environmental
Protection (FDEP) Hurricane Opal recovery effort in the Florida panhandle during the month of
October, 1996. The airborne laser swath system survey was conducted by the manufacturer of the
system, Optech, Inc., of Canada, using Florida Department of Transportation (FDOT) aircraft and
personnel. Additional support was provided by the U.S. Geological Survey. Personnel from the
University of Florida and FDEP were onhand for collection of the laser data. The laser data
discussed in this report were collected on 16-17 October, 1996. The conventional ground truth
surveys discussed in this report were collected by personnel of the UF Coastal & Oceanographic
Engineering Department on 11-13 October, 1996, as part of an ongoing study of beach recovery
following Hurricane Opal1.

Figure 1.1 indicates the location of the ground survey sites and the flight line for the laser
swath survey. The four ground survey sites include Pensacola Beach in Escambia Co., Navarre in
Santa Rosa Co., Miramar Beach in Walton Co., and Panama City Beach in Bay Co. Each site is
comprised of approximately twenty profiles, roughly half of which lie in developed areas and the
other half in undeveloped areas. For example, the eastern (undeveloped) half of the Panama City
Beach site lies in St. Andrews State Park, adjacent to the entrance to St. Andrews Bay.


' Hurricane Opal struck the Florida panhandle on 4-5 October, 1995.















3390000



3370000 -



3350000 -'
Pei


3330000



3310000 -



3290000



3270000 -
450000


470000 490000 510000 530000 550000 570000 590000

EASTING (m, UTM Zone 16, NAD 1983)


610000 630000 650000


Figure 1.1 Location map of study area in the Florida panhandle. The four ground truth survey sites
are shown in the figure along with the flight line of the airbome laser swath mapping system.


CO
0)
r~j








0)
Z


0
z






I

z








A detailed description of the laser data collection and analysis is provided by Carter et al.,
(1997) in the PROJECT LASER Final Report. The reader is referred to this report for specific details
concerning the laser equipment specifications, data collection procedures, and other system
information.

The data collected by the LASER Swath survey system are delivered in SI units. Where
useful, these data have been converted to English units for comparison of beach profiles along
established FDEP monuments, which are documented in English units.








2.0 DATA COLLECTION


The laser swath mapping system consists of three primary components. The first
component is the laser itself and its associated equipment (power supply, optics, etc.). The second
component is a Global Positioning System (GPS) consisting of ground based units and an airborne
unit. The third component is the data collection equipment necessary to store information from
the laser and GPS equipment. The first two components are discussed briefly herein. Again, the
reader is referred to Carter et al., (1997) for details of the laser swath mapping system.

2.1 Laser equipment

The basis for laser swath mapping is that the travel time of a pulse of laser light directed
at an object and reflected back from that object (in this case, the ground) can be measured very
accurately. Given the characteristics of the laser unit itself, the speed of the laser pulse is also
known. Given those two pieces of information, the distance between the laser pulse source and
the object of interest can be determined with a high level of confidence.

A major advantage of the present airborne laser swath mapping system lies in the "swath"
portion of the name of the system. Included with the optics of the laser pulse equipment is an
oscillating mirror which directs the laser pulses along a sweeping path beneath the aircraft. The
obvious advantage to this system as compared to fixed beam mapping systems is that a wide
"swath" of land (or water) can be surveyed beneath the aircraft without requiring a direct flyover
of each point of interest. This allows the aircraft to fly, for example, directly along the shoreline
while collecting millions of data points 100 m or more to either side of the direct flight-line.

The system employed in the present survey operated at a rate of 5,000 pulses per second.
The oscillating mirror was operated at a frequency of 25 oscillations per second. These parameters,
combined with a flight altitude and speed of 344 meters and 72 meters per second, respectively,
resulted in the determination of ranges at points spaced a maximum of 2.9 meters apart between
scan lines and 1.5 meters apart along scan lines. Two datasets were collected, one on the westward
flight and the other on the return eastward flight, totaling over 30 million individual datapoints.

2.2 Positioning Equipment

While the laser equipment provides data describing the distance from the laser in the
aircraft to the point on the ground at which it is directed, other means must be used to determine








the actual geographic location of the targeted point. This is accomplished via the use of Global
Positioning System (GPS) equipment and an inertial navigation unit which provides roll, pitch, and
yaw data for the aircraft during flight.

Briefly, GPS relies on the broadcast of position data from 21 orbiting satellites. Using the
data from four or more satellites, a single, non-military GPS receiver can determine its position on
the earth to within approximately 100 meters (horizontal). Using two GPS receivers, one of which
is a correcting GPS receiver located at a known control position, the location of the other, roving,
receiver can be determined much more accurately using the corrections from the ground receiver
(on the order of centimeters in some cases). For higher accuracy, differential phase differences
using the carrier frequency of the satellite signal are employed (Dana, 1995).

In the present system, a ground-based differential GPS receiver was located in Walton
County (see Figure 1.1), from which corrections for the aircraft-based roving receiver were
collected. Both receivers collected data throughout the flight. The GPS data at each receiver was
time-tagged for later post-processing with the laser range data.

Figure 2.1 depicts a sample output product of the system. The figure illustrates the density
of the collected survey points. As the figure indicates, the density of the collected points is quite
high over land, but drops significantly over water, where the reflecting surface angle reduces the
laser pulse returns to the system. It should be noted that this laser swath system is not a water-
penetrating system; thus no bathymetric information is directly obtained. The shaded relief map
used in the figure was generated from the collected data points using commercial software.

2.3 Conventional Ground Survey

Figure 1.1 indicates the location of four sites along the Florida panhandle shoreline where
beach profiles were collected prior to the laser mapping flight. At each site, 20 profiles were
surveyed from pre-established FDEP monuments. Each site is approximately 3 km (1.9 miles) in
length. The profiles were spaced approximately 150 km (500 ft) apart.

Surveys were performed using standard level, rod, and tape measure techniques. The
azimuth of the profiles was controlled only to within approximately 3 or 4 degrees. It is noted that
the profiles collected as part of this comparison do not necessarily align with historical profiles at
FDEP monuments, as the published FDEP azimuths did not guarantee a clear line of sight and/or
a truly shore-normal profile line.









3.360.890


3.360,870






3.360.850-*+4


3,360,830-






3,360,810-


3,360,790-






3.360.770-


3,360,750-?
558,950


558,970 558,990 559,010 559,030


-55
559,050


EATING (m, UTM NAD 1983)


Figure 2.1 Depiction of the density of surveyed points collected by the LASER swath
survey system. Each black crosshair represents an XYZ data point
measured by the system. The shaded relief map depicts the relief in the
vicinity of the public parking lot (East end) in Miramar Beach, Walton Co., FL.








3.0 DATA REDUCTION


Post-processing of the GPS and laser-range data is necessary to provide a user with a file
of X-Y-Z data points typically used in surface-mapping or survey applications. The GPS system
provides position data in an earth-centered, earth-fixed Cartesian coordinates. Using the GPS data
from both receivers, the position of the aircraft laser is determined, and then the position of the
targeted spot on the surface is calculated using the time series of range, mirror angle, and
navigational corrections (which correct for tilt, pitch, etc., while in flight). The post-processed
product supplied to Project LASER (Carter et al., 1997) consisted of ASCII-format X-Y-Z files
consisting of horizontal position points in Universal Transverse Mercator Zone 16 coordinates
(UTM, NAD 1983) and vertical elevation points referenced to the GPS ellipsoid height2.

Further post-processing for the present report is outlined as follows:

Conversion of UTM horizontal coordinates to geographic (latitude-longitude)
coordinates to provide as input to the GEOID model (see below). This was
accomplished using CORPSCON software (USACE).
Calculation of geoid height at each horizontal coordinate measured. The geoid
height describes the gravitational potential of the earth at any point. Various
models exist to describe the geoid. In the present study, GEOID96 was used
(Milbert, 1996).
Conversion of ellipsoid height to orthometric height (approximately equivalent to
National Geodetic Vertical Datum, 1929, the mean sea level measured in 1929).
Orthometric height provides data relative to the locally level datum.
Creation of final laser data file consisting of horizontal coordinates in UTM NAD
1983 coordinates, and vertical elevations relative to NGVD 1929 datum.

The irregularly spaced data were then sectioned for each of the four sites shown in Figure
1.1. After sectioning, one 3-km file consisted of anywhere between 150,000 and 200,000 data points.
Using commercial software (SURFER, AXUM) the data were then gridded and plotted to produce
shaded relief maps, contour plots, and profile sections. Figure 3.1 (a and b) presents a sample of
the output from the laser data.




2The GPS ellipsoid height is a mathematical representation of the ellipsoidal shape of the earth.















3,356,700



r

3,356,600





3,356,500 0
491,500


491,600 491,700 491,800 491,900
EASTING (m, UTM Zone 16, NAD 1983)


(a)


S-Gulf of Mexico




(b)




Figure 3.1 Examples of products produced from laser swath mapping system. The upper plot
depicts a shaded relief map and elevation contours (in m above NGVD) in the vicinity
of FDEP monument R-139 in Escambia Co., FL. The lower plot (b) depicts a 3-D
perspective view of the same area.


-8-


492,000


-P. ns-~b
rl









4.0 Profile Comparison


Using the SURFER software (Golden Software, Inc.), vertical slices were computed from the
topographic grids generated from the laser data at each site. These slices were then compared to
the ground truth surveys collected via conventional means. This section describes the results of
that comparison. Appendix A contains plots of all 82 profiles taken from both methods.

The primary objective of this report is to assess the agreement of the laser data compared
to the ground truth surveys. This agreement was measured as the root-mean-square error of each
profile. At each profile, the average elevation difference between the laser and ground truth data
was computed. This difference represents the systematic error in the system3. The average
difference was removed from each profile (this step represents the calibration of the data), then the
RMS error was computed from each surveyed point along the ground truth profile.

One unique situation that arises from the use of high-density laser mapping techniques is
that the system will include data collected from anything it strikes, such as buildings, cars,
telephone poles, and even people. This presents some difficulty in determining the beach profiles
in highly developed coastal areas. Figure 4.1 illustrates this situation. This profile, located in
Walton County, runs between two closely spaced houses. The interpolation program used to create
the topographic grid must use points in the vicinity of the grid node to determine the elevation.
As shown in Figure 4.1, between buildings the interpolation routine for the uncalibrated laser data
profile is using points both on the ground and on the buildings. This presents a situation in which
a comparison of the surveyed data points and the laser data is clearly inappropriate.

To avoid this problem, a cutoff value of maximum elevation difference was established.
Any computed elevation difference between the laser data and the ground survey greater than a
set value would not be used in the determination of RMS or average error. Three feet was chosen
as the cutoff value in order to accurately determine the systematic and RMS errors. In addition,
laser data points corresponding to ground survey points below the water line were excluded from
the RMS calculation. For the profile shown in Figure 4.1, the systematic error is approximately 1.8
ft (55 cm). The laser data is lower, relative to the ground truth surveys. This is true of all profiles
discussed in this report. The calibration of the data set is discussed elsewhere in this chapter.


'In this context, the systematic error in the system includes both the laser data and the ground truth data collection
systems. While this error should not be assigned strictly to one or the other, it is apparent that the laser mapping
system contains the greater portion of the systematic error, likely due to the lack of field calibration at the time of
data collection.












3,361,05


3,361,00 R-1.5

OLD US 98
3,360,95


3,360,900- .. .


3,360,85


3,360,80
557,900 558,000 558,100 558,200
EASTING (m, UTM Zone 16, NAD 1983)


558,300


Walton Co. R-1.5

10/96 Survey
V 10/96 LASER (E to W)

SI structure







Gul of Mexico


500


100 200 300 400
Distance seaward of monument (ft)


Figure 4.1


Example of profile lying between two buildings and the
resulting effect on the profile slice from the laser data grid.








4.1 Results


To begin the analysis, the east-to-west flight laser data and the west-to-east flight laser data
were compared in the same manner as the ground truth profiles in order to inspect the
repeatability of the data. This analysis indicated an overall systematic error of approximately 0.25
ft (7.6 cm). The analysis also yielded an RMS error of approximately 0.55 ft (17 cm) for all profiles
in which both sets of flight data were available (west-to east data in Santa Rosa Co. were not
available). Figure 4.2 illustrates a profile in Escambia Co. (R-144). This figure suggests that there
may be a systematic error in the calibration of the inertial navigation system or in the alignment of
the laser unit itself. The profiles appear to exhibit a "tilt" from north to south (i.e., perpendicular
to the flightpath). This error, which involves the roll of the aircraft, affects the systematic error as
well as the RMS error calculations of the profile comparisons in this study. Factors affecting the
degree of error associated with this tilt include the length of the individual profile and the location
of the profile relative to the laser swath (rather, the location of the monument and profile relative
to the flightline). It is anticipated that a proper field calibration would have significantly reduced
this source of systematic (and, potentially, RMS) error.


Escambia Co. R-144


20


15


(,
z10

S5
16


-5 I II I I I I I I I I I I I I I
100 200 300 400 500 600
Distance seaward of monument (ft)


Figure 4.2 Comparison of east-to-west and west-to-east flight data for profile R-144 in Escambia
Co. The figure illustrates the 'tilt' error suggested in the data set. On the landward end
of the profile, the westerly data lie above the easterly data, and vice-versa for the
Gulfward end of the profile.


-N 10/96 LASER (Wto E)
_ ____10/96 LASER (E to W)




/ G uf of Mexico


. . . . . . ..-- -----


c









Table 4.1 presents the results of all RMS calculations for the four sites. The average
systematic error over the entire area was found to be 1.49 ft (45 cm). The average RMS error from
all profiles was found to be 0.68 ft (20.7 cm). Using a limited number of highly controlled ground
profiles, Carter et al. (1997) reported RMS errors of less than 10 cm. Figure 4.3 indicates the
variation of systematic error along the flightline. The figure suggests that the systematic error
decreases from east to west over the flightline by as much as 0.8 ft (24 cm)4. Carter et al. (1997)
attribute this variation to the use of the less accurate, broadcast satellite ephemeris method for
positioning rather than a phase difference satellite ephemeris5.


Figure 4.4 depicts the alongshore variation in RMS error for all profiles. No significant
alongshore trend in the RMS error is present. The increased scatter of data in the Walton Co. and
Bay Co. sites may be due to the increased level of development in those areas. Increased
development in these areas results in more profiles running between buildings (see Figure 4.1) and
subsequently, fewer valid laser data points to use on each profile in the RMS error calculation.



Table 4.1 Summary of Systematic and RMS Errors Computed for Each Survey Site


Site Flight Number of Systematic Error RMS
Profiles (ft) Error (ft)

Bay Co. E to W 20 2.10 0.66

WtoE 20 2.01 0.70

Walton Co. E to W 20 1.49 0.68
WtoE 20 1.04 0.85

Santa Rosa Co. E to W 20 1.63 0.55

Escambia Co. E to W 22 1.29 0.57

WtoE 22 1.00 0.75

Average 1.50 (45 cm) 0.68 (21 cm)
* W to E laser data in Santa Rosa Co. was not collected.


4 The fact that the systematic error actually decreases in the westerly direction, heading away from the
base station, is completely fortuitous and is not to be construed as relating to the distance from the base
station.

5 ephemeris the satellite's actual position on it's orbit in space about the earth.


-12-













8


7


6
SANWA ROSA C WALTON CO.
SITE SITE
5 ITE

B AY CO. SI1 E
.: 4

.o-





SI I I I I ----
= Gulf rfMexico


450000 470000 490000 510000 530000 550000 570000 590000 610000 630000 650000
EASTING (m, UTM Zone 16, NAD 1983)



Figure 4.3 Average error in each profile for both the east-to-west and west-to east flights. This error may be considered
as the systematic (or offset) error between the laser and ground truth datasets. The line represents
a least-squares linear fit of the average error.




























CL
0
as



0
C,,


450000 470000 490000 510000 530000 550000 570000 590000

EASTING (m, UTM Zone 16, NAD 1983)


610000 630000 650000


Figure 4.4 RMS error in each profile for both the east-to-west and west-to east flights. This error may be considered

as the level of agreement between the laser and ground truth datasets. The line represents

a least-squares linear fit of the RMS error.








The profiles plotted in Figure 4.5 indicate the agreement attained when the laser data
profiles are "calibrated" using the average error computed at profile. In this figure the distortion
in scale has been reduced to highlight the horizontal and vertical agreement. The systematic error
in elevation between the profiles in the upper plot is 2.28 ft (69 cm) while the RMS error of the
calibrated profile is 0.67 ft (20 cm). The systematic error in the profiles in the lower plot is 1.47 ft
(45 cm) and the associated RMS error in the calibrated data is 0.56 ft (17 cm).

4.2 Sources of Error

This section discusses a few of the possible sources of error that contribute to both the offset
error and the accuracy. This is by no means an exhaustive discussion of the accuracy of each
individual component of the laser swath mapping system. The reader is referred to Carter et al.,
1997, for details of the system specifications.

4.2.1 Calibration The largest and most evident source of error is also relatively easy to correct in
the post-processing stage. The systematic offset error measured in the laser data (approximately
1.5 ft or 45 cm, on average) is most likely attributable to the lack of a field calibration for the laser
dataset. Logistical problems and aircraft damage on the last day of flight prevented the calibration
of the laser mapping unit at the site. It is anticipated that a proper field calibration would have
eliminated most of the systematic error present in the data.

4.2.2 GPS Positioning Only one base station was used to determine the corrections for the
airborne receiver. It is anticipated that increased distance from the base station degrades the
accuracy of the GPS corrections (i.e., the corrections computed by the base receiver may no longer
closely apply to the roving receiver). Unfortunately, on the day of the flight, additional ground
based receivers, which were in position along the flightpath, did not capture a continuous set of
GPS corrections data, making the post-flight data-processing cumbersome. It is anticipated that
the use of the additional ground receivers would improve the overall accuracy of the system along
the entire flightline.

4.2.3 Ground Surveying Techniques The ground truth surveys themselves are a likely contributor
to the error computed in the profiles. The use of rod and chain techniques introduces some level
of error (on the order of less than 1 m, horizontal). More important, however, is the control of the
survey azimuth. It is estimated that the azimuth accuracy is at best two or three degrees. This
plays an important role in the comparison since the slices made through the topographic grids are
based on the azimuth reported from each ground truth profile. While the variation alongshore on
the beach is expected to be minimal, this source of error can clearly affect the accuracy and is
exacerbated along longer profiles where the survey monument is set further from the shoreline.
























50 100 150 200 250 300 350


0 50 100 150 200 250 300 350
Distance seaward of monument (ft)

Figure 4.5 Examples of beach profile comparison before and after calibration using systematic error of each profile.


400


400








5.0 CONCLUSION


The results of the present study indicate that the laser swath mapping system is quite
capable of producing accurate beach profile data. The agreement of the system, as compared to the
ground truth beach profiles collected as part of this study, is estimated to be approximately 0.68 ft (20
cm) in vertical elevation (following removal of the mean, systematic error). For purposes of most
coastal engineering beach profile analysis, such as determining shoreline position, this level of
accuracy is deemed more than sufficient. The accuracy of the elevation measurements should be
held in proper perspective when using these data for volumetric calculations, particularly with
other, non-laser data profiles. For example, over a 100-ft segment of beach profile, an elevation
error of 0.7 ft could result in an error of 2.5 cubic yards of sand per foot of shoreline. Stretched over
a great distance between profiles (1,000 ft for example) this would translate to 2,500 cy. It is noted,
however, that the use of RMS error implies that the errors are distributed normally about the mean
value and thus an overestimate in one reading along a profile may be balanced by an
underestimate in the next reading.

The offset error measured in the laser dataset is attributed to the lack of proper calibration
in the field at the time of data collection. It is anticipated that a proper calibration would have
removed most of the offset error. In addition, the use of additional ground-based GPS receivers
is expected to further improve the accuracy of the laser swath mapping system.

Given the accuracy and volume of data collected in such a rapid and relatively inexpensive
manner, laser swath mapping appears to be an excellent means of documenting shoreline changes,
for both position and volume change. Such a system could prove invaluable in assessing storm
damage across a wide area (as in Hurricane Opal) in a short period of time. Concurrent with the
opinions of Carter et al., (1997) it is recommended that the laser swath mapping technique be
implemented as soon as possible for a variety of beach monitoring purposes.


6.0 REFERENCES


Carter, W.E.; Shrestha, R.L.; Thompson, P.Y.; and Dean, R.G., "Project LASER, FINAL REPORT,"
1997, Department of Civil Engineering, University of Florida, Gainesville, FL, 32611.

Dana, P.H., "The Geographer's Craft Project", 1995, Department of Geography, The University of
Texas at Austin. Available via internet: www.utexas.edu/depts/grg/gcraft

Milbert, D.S., and Smith, D., "NGS GEOID96 Model," National Geodetic Survey Geoid Computation
Program. Available via internet: ftp.ngs.noaa.gov/GEOID/geoid.html




















APPENDIX A


GROUND TRUTH PROFILES

&

UNCALIBRATED LASER DATA PROFILES


*A-1










Bay Co. R-85

10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








GL f of Mexico


100


500


200 300 400
Distance seaward of monument (ft)


0 100 200 300
Distance seaward of monument (ft)


400


500





























500


0 100 200 300 400
Distance seaward of monument (ft)


Bay Co. R-86.5

1- 0/96 Survey
_____10/96 LASER (E to W)
10/96 LASER (W to E)








Gul of Mexico


100


200 300
Distance seaward of monument (ft)


400


500


A-3










Bay Co. R-87

10/96 Survey
S- 10/96 LASER (E to W)
10/96 LASER (W to E)








Guf of Mexico


I I T I I I I I I T_


100


500


200 300 400
Distance seaward of monument (ft)


500


100 200 300 400
Distance seaward of monument (ft)










Bay Co. R-88


500


100 200 300 400
Distance seaward of monument (ft)


Bay Co. R-88.5






Monument lies on seaward e ge of seawall,
no significant sub-aerial data to compare.


Gul of Mexico


i .I 1 ili l ll I


100


200 300
Distance seaward of monument (ft)


400


500










Bay Co. R-89
10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








Gulf of Mexico
I T I


100


0 100


200 300
Distance seaward of monument (ft)


200 300
Distance seaward of monument (ft)


400


400


500


500










Bay Co. R-90


500


100 200 300 400
Distance seaward of monument (ft)


Bay Co. R-90.5

10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








Gul' of Mexico

\ i J ii iA


100


200


300


400


500


Distance seaward of monument (ft)










Bay Co. R-91

I--- 10/96 Survey
I10/96 LASER (E to W)
10/96 LASER (W to E)








Gulf of Mexico


100


200 300
Distance seaward of monument (ft)


400


500


Bay Co. R-91.5
-- 10/96 Survey
- ____10/96 LASER (E to W)
10/96 LASER (W to E)








Gul of Mexico


I- l i ll_^^ ^^ I^^ ^ > ^ ^ -- ^* ^ -^ I^^ ^ l^ ^ ^ ^- 'i l ^ il li ir II


100


200 300
Distance seaward of monument (ft)


400


500


500










Bay Co. R-92

S 10/96 Survey
___- 10/96 LASER (E to W)
10/96 LASER (W to E)








Sf of Mexico


100


200


300


400


500


600


Distance seaward of monument (ft)


Bay Co. R-92.5

10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








Gui of Mexico


100


200


300


400


500


Distance seaward of monument (ft)


A-9










Bay Co. R-93


500


0 100 200 300 400
Distance seaward of monument (ft)


Bay Co. R-93.5
S 10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








Gul of Mexico


\ V ^Ji J ii


100


200 300
Distance seaward of monument (ft)


400


500


A-10




























0 100 200 300 400
Distance seaward of monument (ft)


0 100 200 300
Distance seaward of monument (ft)


400


A-11


500


500










Walton Co. R-1

10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








Gu f of Mexico
_I\ T


100


0 100


200 300
Distance seaward of monument (ft)


200 300
Distance seaward of monument (ft)


400


400


500


500


A-12










Walton Co. R-2


0 100 200 300 400
Distance seaward of monument (ft)


Walton Co. R-2.5


100 200 300
Distance seaward of monument (ft)


400


A-13


500


500










Walton Co. R-3


100 200 300 400
Distance seaward of monument (ft)


0 100


200 300
Distance seaward of monument (ft)


A-14


500


400


500










Walton Co. R-3A


500


0 100 200 300 400
Distance seaward of monument (ft)


Walton Co. R-3A.5

10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)







k Gull of Mexico


100 200 300
Distance seaward of monument (ft)


400


500


A-15










Walton Co. R-4


0 100 200 300 400
Distance seaward of monument (ft)


Walton Co. R-4.5


0 100 200 300 400
Distance seaward of monument (ft)


A-16


500


500







Walton Co. R-5


0 100 200 300 400
Distance seaward of monument (ft)


Walton Co. R-5.5


100 200 300
Distance seaward of monument (ft)


400


A-17


500


500










Walton Co. R-6

S\ -- 10/96 Survey
I 10/96 LASER (E to W)
10/96 LASER (W to E)








I Gulf of Mexico
: __^v____


100


Walton Co. R-6.5


200 300
Distance seaward of monument (ft)


0 100 200 300
Distance seaward of monument (ft)


400


500


400


500


A--18










Walton Co. R-6A


0 100 200 300 400
Distance seaward of monument (ft)


Walton Co. R-6A.5


0 100 200 300
Distance seaward of monument (ft)


400


A-19


500


500










Walton Co. R-7


0 100 200 300 400
Distance seaward of monument (ft)


Walton Co. R-7.5


0 100 200 300
Distance seaward of monument (ft)


400


A-20


500


500










Walton Co. R-8


0 100 200 300 400
Distance seaward of monument (ft)


Walton Co. R-8.5


0 100 200 300
Distance seaward of monument (ft)


400


A-21


500


500








NOTE: West to East LASER data unavailable for this site.


Santa Rosa Co. R-187


0 100 200 300 400
Distance seaward of monument (ft)


Santa Rosa Co. R-187.5


0 100 200 300 400
Distance seaward of monument (ft)


A-22


500


500










Santa Rosa Co. R-188

S 10/96 Survey
10/96 LASER (E to W)









S\ G f of Mexico


I-- I I-


100


200


300


400


500


Distance seaward of monument (ft)


Santa Rosa Co. R-188.5


0 100 200 300
Distance seaward of monument (ft)


A-23


400


500










Santa Rosa Co. R-189
!5 I I
S 10/96 Survey
0- 10/96 LASER (E to W)


15


10


5
15 :--------------------


-- Guf of Mexico

0


-5 I


100


200


300


400


500


Distance seaward of monument (ft)


Santa Rosa Co. R-189.5


0 100 200 300 400
Distance seaward of monument (ft)


A-24


500










Santa Rosa Co. R-190


0 100 200 300 400
Distance seaward of monument (ft)


Santa Rosa Co. R-190.5


0 100 200 300
Distance seaward of monument (ft)


400


A-25


500


500










Santa Rosa Co. R-191


0 100 200 300 400
Distance seaward of monument (ft)


0 100


200 300
Distance seaward of monument (ft)


A-26


500


400


500










Santa Rosa Co. R-192


0 100 200 300 400
Distance seaward of monument (ft)


A-27


500










Santa Rosa Co. R-193


0 100 200 300 400
Distance seaward of monument (ft)


Santa Rosa Co. R-193.5


0 100 200 300 400
Distance seaward of monument (ft)


A-28


500


500










Santa Rosa Co. R-194


0 100 200 300 400
Distance seaward of monument (ft)





Santa Rosa Co. R-194.5


0 100 200 300
Distance seaward of monument (ft)


400


A-29


500


500










Santa Rosa Co. R-195


100 200 300 400
Distance seaward of monument (ft)


Santa Rosa Co. R-195.5


0 100 200 300
Distance seaward of monument (ft)


400


A-30


500


500










Santa Rosa Co. R-196

10/96 Survey
10/96 LASER (E to W)








'" Gu f of Mexico


\------ E ------


100


200 300
Distance seaward of monument (ft)


400


500


Santa Rosa Co. R-196.5


0 100


200 300
Distance seaward of monument (ft)


A-31


400


500










Santa Rosa Co. R-197
25I I
10/96 Survey
20 10/96 LASER (E to W)


> 15


Z
|- 10 ---------------



w Gu'f of Mexico

0


-5 . . .
0 100 200 300 400 500
Distance seaward of monument (ft)


A-32










Escambia Co. R-133

S 10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








Gu f of Mexico

i :------ i i i i i I i--- i


100


200


300


400


500


Distance seaward of monument (ft)


Escambia Co. R-133.5


0 100


200 300
Distance seaward of monument (ft)


A-33


400


500










Escambia Co. R-134


0 100 200 300 400
Distance seaward of monument (ft)


Escambia Co. R-134.5


0 100


200 300
Distance seaward of monument (ft)


A-34


500


400


500










Escambia Co. R-135


0 100 200 300 400
Distance seaward of monument (ft)


0 100


200 300
Distance seaward of monument (ft)


A-35


500


400


500










Escambia Co. R-136

---- 10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








SG If of Mexico

--__ f ,___


100 200
Distance seaward


Escambia Co. R-136.5


0 100


300
of monument (ft)


200 300
Distance seaward of monument (ft)


400


400


A-36


500


500










Escambia Co. R-137


0 100 200 300 400
Distance seaward of monument (ft)


Escambia Co. R-137.5


0 100 200 300
Distance seaward of monument (ft)


400


A-37


500


500










Escambia Co. R-138

10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)







Gulf of Mexico


100


200 300
Distance seaward of monument (ft)


Escambia Co. R-138.5


100


200 300
Distance seaward of monument (ft)


400


400


500


500


A-38










Escambia Co. R-139


0 100 200 300 400
Distance seaward of monument (ft)


Escambia Co. R-139.5


0 100


200 300
Distance seaward of monument (ft)


A-39


500


400


500










Escambia Co. R-140


900


500 600 700 800
Distance seaward of monument (ft)


Escambia Co. R-140.5
-- 10/96 Survey
10/96 LASER (E to W)
10/96 LASER (W to E)








Gul' of Mexico


200 300 400
Distance seaward of monument (ft)


500


600


A-40


400


100










Escambia Co. R-141


100 200 300 400
Distance seaward of monument (ft)


Escambia Co. R-141.5


200


300 400
Distance seaward of monument (ft)


500


A-41


500


-51
100


600










Escambia Co. R-142


0 100 200 300 400
Distance seaward of monument (ft)


Escambia Co. R-142.5


200 300 400
Distance seaward of monument (ft)


500


A-42


500


600










Escambia Co. R-143


0 100 200 300 400
Distance seaward of monument (ft)


Escambia Co. R-144


200


300 400
Distance seaward of monument (ft)


500


A-43


500


100


600




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