INVESTIGATING THE PRECISION OF AN UNMANNED AERIAL PHOTOGRAMMETRIC BEACH SURVEY WITHOUT

GROUND CONTROL POINTS

Paul Aldersley BSc (Hons) Ocean Exploration

Plymouth University

School of Marine Science and Engineering

OBJECTIVES

• Setting the scene

•Methodology

•Results

•Conclusions

• Future Research

Setting the scene:

• Quicker than Terrestrial Survey • Cheaper than a Manned Aerial Survey • Little research into UAV over a beach • None without GCP

Why an unmanned aerial vehicle (UAV) survey and why research it?

Setting the Scene: Photogrammetry without Ground control Points

“The science of measuring in photos” (Linder 2006)

Ground Control points Structure From Motion No Ground Control Points

Setting the Scene: The UAV • The Topcon Sirius Pro UAV

No Ground Control Points

Undertake an aerial digital photogrammetric survey of a suitable beach

Complete a comparative terrestrial survey of the same area using a quad bike and

RTK GPS

Produce digital elevation models (DEMs) using the data obtained from each survey

method & compare the results and draw conclusions.

Setting the scene: Aim & Objectives To test the precision of an unmanned aerial photogrammetric beach survey without the use of ground control points.

Methodology: Survey Location

Methodology: Surveys

Both surveys OSGB36 Ref. Frame tied in with local OS Rinex Stations

Aerial Two Flights. Base station static GPS RTK Link Base station to aircraft

Terrestrial Established Base station Point Linked to Rover GPS on Quad Bike

Methodology: Post processing - workflow

CSV XYZ data DEM produced in ArcGIS

Orthophotos & DEMs produced in Agisoft Photoscan

DEMs imported into ArcGIS

Results Aerial Terrestrial

Orthomosaic “rubber sheeted” over DEM using Virtual Surveyor Software

Results: Comparing data

• Comparing elevation values only • Root mean Square Error of 0.11m • Existing work – with GCP 0.05m –

but not flat beach • Lidar 0.29m

Difference (m)

Results: Profiles

-3.5000

-2.5000

-1.5000

-0.5000

0.5000

1.5000

2.5000

0.00 50.00 100.00 150.00 200.00 250.00 300.00

Ele

vati

on

re

lati

ve t

o m

ean

se

a le

vel.

(m)

Distance Across Beach (m)

GCP 10-18 Profile

Terrestrial_DEM

UAV_DEM

GCP

-3.00

-2.50

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00

Ele

vati

on

re

lati

ve t

o M

ean

se

a le

vel(

m)

Distance Across Beach (m)

GCP 14 - 15 Profile

Terrestrial_DEMUAV_DEM

GCP

14

15

Results: A closer look

Results: Profile across a pool

-3.5000

-3.0000

-2.5000

-2.0000

-1.5000

-1.0000

-0.5000

0.0000

0.5000

0.0000 50.0000 100.0000 150.0000 200.0000 250.0000

Ele

vati

on

re

lati

ve t

o m

ean

se

a le

vel (

m)

Distance Across beach (m)

New profile

Terrestrial DEM

Aerial_DEM

RESULTS: WATER?

Conclusions/Learning

• Two separate surveys • Repeated Surveys • Know the equipment

Future Study

•Work on the impact of water and mitigation •Direct comparison of accuracy

Acknowledgements: I am grateful for the support of the following people in assisting me to get to this current stage of my honours project. • Mr Martin Read - Project Advisor . • Dr Vic Abbott – Tutor and Technical Project Advisor. • Dr Tim Scott – Co-ordinator of the Coastal Observation team for his

advice and support on the day of data collection and since.

• The Coastal Observation Project team for running the terrestrial survey on the day and sharing their data.

• Topcon Positioning GB & Ireland for the use of their Sirius Pro Unmanned Aerial System.

• Mat Kellett from Topcon for providing the survey expertise on the day and

for his advice pre and post the survey flights. • George Ollis-Brown and Dom Williamson for their help on the survey day.

References Geoconnexions.com. 2016 Http:/www.geoconnexions,com [Accessed 7th March 2016] Linder, W. 2nd edition.2006. Digital Photogrammetry, A Practical Course. Berlin: Springer. Puget Sound River History Project. 2016. Available at http://riverhistory.ess.washington.edu/photo.php [Accessed 1st March 2016] RICS. 2010. Vertical aerial photography and digital imagery practice standards. 5th Edition. Available at : https://communities.rics.org/gf2.ti/f/200194/4265829.2/PDF/-/RICS_Vertical_aerial_photography_and_digital_imagery_2010_5th_ed_final_online_version.pdf Topcon: Topcon Sirius Pro UAV system literature.

Thanks - Questions