U.S. Department of the Interior

U.S. Geological Survey

Evaluation of Terrestrial Lidar Tool for Monitoring GeomorphChange at Archaeological SiteGrand Canyon National ParkBrian Collins, Ph.D.USGS - Western Earth Surface Processes, Menlo Park, CalifoPresentation to the Glen Canyon Dam Adaptive Management Technical Work Group Meeting, Phoenix, ArizonaApril 8, 2008, 3:45pm
Outline

 Terrestrial lidar

 Background

 Project 1 – Comparison of total station 

collection for gully thalweg

 Results

 Project 2 – Whole site change detection 

terrestrial lidar

 Preliminary results

 Future directions
Terrestrial Lidar

 A new technology

 Used for documentation of existing conditions (including 

widespread use in archaeology)

 Used for change detection of geomorphic landscapes 

(landslide, cliff erosion)

 Not yet used for high resolution, small-scale change 

detection

 Capabilities

 Collection of thousands of points per second Accuracy of several millimeters to centimeters Range of 2m to 1000m Units can be made portable (USGS focus for difficult 

environmental conditions)

 Issues with reflectivity, laser divergence, laser 

obliqueness, all affect data quality

 Summary

 A high-resolution, highly accurate survey device for 

documenting and monitoring landscape surface change
How does it work?

Detector Detector

Rotating Rotating 

mirror

Laser

pulse

and

Laser

pulse

and

position

an

position

and

Pulsed laser Pulsed laser 

diode

Scanning head Scanning head
How does it work?

Laser

Points 

Filtering Filtering

Surface Surface 

building building
Project 1 – Survey Method Com

 Purpose: compare site impacts 

and gully thalweg data collected between total station (TS) and terrestrial lidar (LIDAR)

 Topographic data collection

 Focus only on gully thalwegs Point accuracy Data density Feature detection

 Site impacts

 Total survey time Time in sensitive area Footstep count
Project 1 – Data Collection

 May 2006 survey effort

 May 2007 impact data 

also used

 Eight sites

 8 compared for impacts 3 compared for 

topographic data

 Results available soon 

(USGS Open File Report – May 2008, 82p.)

Blue = impact evaRed = topographic 
Results: Site Impacts

 Total time in sensitive area is similar between methods For TS, time is concentrated in the gullies For LIDAR, time is concentrated at the instrument, outsi

02468

101214161820

SITE

PERSON HOURS

C:13:006 C:13:336 C:13:099 C:13:348 G:03:041 G:03:002 

- TOTAL DATA C TIME IN SENSIT - LIDAR - TS

Person hours

Site Number
Results: Site Impacts

 Footstep impact is similar between LIDAR and TS methods Footstep locations are concentrated differently LIDAR utilizes two people outside the gullies, TS uses one pers

FOOTSTEP IMPACT

0

100020003000400050006000

C:13:006

C:13:336

C:13:099

C:13:34 8

G:03:041

G:03:002

G

Site Name

Cum ulative Footstep Count

Footstep Count

Site Number
Results: Site Impacts

 Tot

~15

 Tim

pos

 Val

of p(mi

CUMULATIVE AVERAGE MAPPING TIMES

0

102030405060708090

100

Lidar Average TS Average

Mapping Method

Person Hours

G:03:072DG:03:072UG:03:002G:03:041C:13:348C:13:099C:13:336C:13:006

Person hours

Mapping Method
Results: Data Density

~1 m

Orange Blue = 

Site Numbe

AZ:C:13:00

AZ:G:03:04AZ:G:03:07

Lidar derived 

gully thalweg
Results: Thalweg Location

1

2

P

LIDAR Data

5m 

5m

10m15m20m

25m

0 

Gully 2
Results: Long Profile Comparis

420422424426428430432434436438

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Distance Along Section (m)

Elevation above NAD83 Ellipsoid (m)

Lidar DataTotal Station Data
Project 2 – Change Detection E

 Purpose: determine if terrestrial 

lidar is capable of change detection at the centimeter/decimeter scale

 Focus on both gully erosion and 

whole site geomorphic change

 Investigate ability to monitor 

entire archaeologic sites for short- and long-term change
Project 2 – Data Collection

 May 2007 and September 

2007 survey efforts

 Nine sites

 All compared for 

topographic data

 Cross-sections Surface change maps

 Results available 

~August 2008 Red = topographi
Preliminary Results: Site with N

 60 Mile Site Area of stabilized 

cryptogamic soil with incipient gullying

 Archaeological site exists 

over entire area

 Three gullies traverse site 

and discharge to an arroyo that discharges to the Colorado River
Preliminary Results: Surface Chang

May 2007 to September 

2007 Surface Change Map 

at 60 Mile Site

Cross-section 

~50m

~15m

Erosion

Accretion

Minimum De

A

A 
Preliminary Results: Site with C

 223 Mile Upstream Site Area of aeolian deposition 

with pronounced gullying

 Archaeological sites are 

immediately adjacent to gullies

 Three gullies traverse site 

and discharge directly into Colorado River
Preliminary Results: Surface C

10cm Contour Maps of 223 Mile-US Site – Gu

May 2007 September 
Preliminary Results: Surface Chang

May 2007 to September 2007 Surface Change Map at 

Erosion

Accretion

Plan Area 

Minimum de

~15m x 30m
Future Directions

Courtesy: RieglUSA, Source: NeubaScanning and Photogrammetrical D

 Rapidly changing 

technology

 Higher accuracy – reduce 

model error from ~ 7cm to < 1cm.

 Longer range – lower site 

impact?

 Digital photo draping –

feature identification and monitoring
Conclusions and Future Direct

 Project 1 - complete

 Viable data collection method Saves time in the field Does not reduce site impact appreciably Provides superior data coverage and ability to p

monitoring

 Project 2 – nearing completion

 Change detection is achievable – 10 to 15 cm sc Excellent potential for identifying areas of incipi

 Technology is new – and changing

 Newest generation of lasers addressed existing  Feature and site monitoring via photo draping
Thank you.