A METHOD OF AERIAL STIV WITHOUT REQUIRING OF GROUND CONTROL POINTS
1214
Masahiro HASHIBA , Ichiro FUJITA , Noriyuki NISHIYAMA , Yoko OHTA
1)Fukuda Hydrologic Center Co. Ltd., 2) Faculty of Engineering, Kobe University, 3) Ministry of Land, Infrastructure, Transport and Tourism Hokkaido Regional Development Bureau

COMPARISON OF VELOCITY IN DISTRIBUTION MULTIANGLE IMAGE（Slant view or Ortho view)

Slant view

Slant view

Slant view

Height above ground 20m Height above ground 50m

Slant view

Height above ground 70m Height above ground 100mTHE METHOD OF AERIAL STIV WITHOUT GCPTotal flight distance 3.7km
Elapsed time 21min
250m

Slant_20m
Slant_70m
Slant_130m
Ortho_130m

Slant view

Ortho view

Ortho view

Height above ground 130m Height above ground 100m Height above ground 130m

0.30

0.8

0.20

0.4

0.10

0.0

0.00

12

－10%

0.6

0.4
0.2

0.2
0.4
0.6
0.8
1.0
Average velocity:surveying-GCP(m/sec)

Searching line

281

Searching lines

TimeS-90

LSpace-time Image0（degree)

90

Component in theradial direction

0.4

0.10

0.0

0.00

2456 7 8 9 10 11 12 13 14 15
Transverse section No.

0DIEX method

2018160𝑆𝑥
𝑈 = tan ∅𝑆𝑡Where U [m/s] is velocity,
Sx [m/pixel] is the unit
length scale of the line
segment, St [s/pixel] is unit
scale of time axis, ∅ is angleof STI.

Discharge(m3/sec)

22

40

80

120

160

Transverse distance（m）

200

240

5%-5%

0-10%
Slant
50m

Slant
70m

Slant
Slant
100m 130m
Obs.method

Ortho
100m

Ortho
130m
10%

Pseudo-GCP discharge
Surveying GCP discharge
difference(pseudo-rating curve)

124

10%

100

流速（m/s）
Velocity(m/sec)

26Height（E.L.m）

STIV method

Spectralanalysis0.200%

400
色を変える場合はクリック③STIV analysis

θ

0.8

200

Slant20m

Intensity

0.30

300

5%

2000%

100-5%0-10%
Slant
20m

Slant
50m

Slant
70m

Slant
Slant
100m 130m
Obs.method

Ortho
100m

diffrerence

Discharge(m3/sec)

Divided sectional
method300

1• The three dimensional terrain model was createdusing SfM/MVS, the plane position error at thedistance was from 0.05m to 0.09 m and theheight error was from 0.01m to 0.04m.
• The authors extracted the pseudo-GCP from thepoint cloud.

1.2

Pseudo-GCP discharge
Surveying GCP discharge
difference(pseudo-rating curve)

Velocity(m/sec)②Geometric correction& set the searching lines

Fourier analysis

0.40

COMPARISON OF 2 TYPE DISCHARGE RESULTS

Use the pseudo-GCP instead ofsurveying GCPDistance of Searching line

Slant_50m
Slant_100m
Ortho_100m
Standard deviation

Pseudo-GCP

1515

1.6

1.2

400

GroundControl Point

6 7 8 9 10 11 12 13 14 15
Transverse section No.

Slant_20m
Slant_70m
Slant_130m
Ortho_130m

0.0

Pseudo-GCP from 3D terrain model ① Set the GCP(Ground Control Point) on the image
Pseudo-GCP using point cloud

50.50

10.0

4

2.0Velocity(m/sec)

Average velocity:
pseudo-GCP(m/sec)

The difference in surface flow
velocity was withinapproximately 10% between
surveying-GCP and .PseudoGCP

1.00.83

Surveying-GCP+10%

A post-processing kinematic system “Klau PPKsystem(Klau Geomatics)” compatible with
UAV of “Inspire2(DJI)” .Electronic reference
Enough to 1 flight (1Battery pack)information is imported by post-processing.
UAV zigzag flight of 70% side laps and 85% overlap was able to create a 3D terrain model.
It was possible to about 20 minutes flight to create a terrain model of 300m×250m.

0.40

1.2

1.2

UAV(quad copter)

Slant_50m
Slant_100m
Ortho_100m
Standard deviation

diffrerence

300m

Receiver0.50

1.6
Velocity(m/sec)

Antenna

2.0Standard deviation

By using a UAV (Unmanned Aerial Vehicle), it is possible to measure the river flow by image
velocimetry wherever the place away. However, to perform image analysis, it is necessary to
install the ground control point (GCP) in the image and to set the accurate coordinates to run ageometric correction. In this study, we extract as pseudo-GCP the point cloud of the 3D terrain
model, which was made by Structure from Motion (SfM) using a post-processed kinematic
system by UAV. After we analyzed the surface velocity distribution by Space-Time Image
Velocimetry (STIV) method.

Standard devietion

INTRODUCTION

Ortho130m• A comparisonof thedischarge between using the pseudo GCP and surveying流速コンター図
サンプル
GCP was shown that the difference was within ± 5%, regardless of the divided
sectional method or DIEX (Dynamic Interpolation and Extrapolation) method.

CONCLUSIONS
The authors succeeded to calculate surface flow velocity with the minimum error by
the STIV method using pseudo-GCP which is no requirement of surveying-GCP.