This document summarizes the application of Structure-from-Motion (SfM) photogrammetry for monitoring erosion processes, using the example of Mošćenička Draga in Croatia. SfM photogrammetry was used to generate 3D point clouds and digital elevation models from 2012 and 2013. Comparisons of profiles showed areas of sediment accumulation and erosion. The technique provides a low-cost way to frequently acquire high-resolution terrain models for monitoring landslide and erosion processes.

1. 4th Workshop of the Japanese-Croatian Project on
‘Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods in Croatia’
Split (Croatia), 12-14 December 2013
APPLICATION OF ‘STRUCTURE-FROM-MOTION’
PHOTOGRAMMETRY FOR EROSION PROCESSES
MONITORING, MOŠĆENIČKA DRAGA EXAMPLE
Igor Ružić1, Ivan Marović1, Martina Vivoda1, Sanja Dugonjić Jovančević1, Duje Kalajžić2, Čedomir Benac1, Nevenka Ožanić1
1University of
Rijeka, Faculty of Civil Engineering
2University of Rijeka, IT Services

2. 3
Digital Elevation Model
5
Research idea
7
Tools and resources
9
Examples
10
Conclusions
21
OUTLINE
Structure-from-Motion photogrammetry and 3d point cloud

3. ‘Structure-from-Motion’ (SfM) operates similarly as stereoscopic photogrammetry, 3-D structure can be
resolved from a series of overlapping, offset images.
SfM photogrammetry:
The scene geometry, camera positions and orientation are solved automatically
Approach is most suited to sets of images with a high degree of overlap that capture full three
dimensional structure of the scene viewed from a wide array of positions, or as the name suggests,
images derived from a moving sensor
Developed in the 1990s, this technique has its origins
in the computer vision community
Available various free SfM Softwares
SFM PHOTOGRAMMETRY
What is Structure-from-Motion photogrammetry?

4. A point cloud is a set of data points in some coordinate system.
In a three-dimensional coordinate system, these points are usually defined by X, Y, and Z coordinates, and
often are intended to represent the external surface of an object.
In geographic information system, point clouds are one of the sources to make digital elevation model of the
terrain. The point clouds are also employed in order to generate 3D model of urban environment, e.g.
3D point cloud can be generated using: 3d scanners, laser scanning, terrestrial radar, photogrammetry, SfM
photogrammetry etc.
3D POINT CLOUD
3D point cloud

5. DEM HISTORY
What is digital terrain model?
Robers (1957) first proposed the use of the digital computer with
photogrammetry as a new tool for acquiring data for planning and
design in highway engineering
DTM
Miller & LaFlamme (1958) described the development in detail
and introduced the concept of the digital terrain model
“The digital terrain model (DTM) is simply a statistical
representation of the continuous surface of the ground by a large
number of selected points with known X, Y , Z coordinates in an
arbitrary coordinate field.” – definition given by Miller & LaFlamme
in 1958
TERMINOLOGY
Digital Elevation Model (DEM) – generic term for altitude grid
Digital Terrain Model (DTM) – ground elevation model
Digital Surface Model (DSM) – ground + cover elevation model
Digital Height Model (DHM) – cover elevation model
DSM
DHM

6. How to produce DEM?
• Existing Contour Map
• Aerial Photograph
• Satellite:
• Optical Remote Sensing
• SAR – Synthetic Aperture Radar
• Laser Scanner
• SfM Photogrammetry
DEM DEVELOPMENT
Digital representation of terrain

7. *James, M. R., & Robson, S., Straightforward reconstruction of 3D surfaces and topography with a camera:
Accuracy and geoscience application, Journal of Geophysical Research, 117, 2012.
RESEARCH IDEA
3D Scanner vs SfM; TLS vs SfM– James*

8. *Westoby, M. J., Brasington, J., Glasser, N. F., Hambrey, M. J., & Reynolds, J. M., “Structure-from-Motion”
photogrammetry: A low-cost, effective tool for geoscience applications, Geomorphology, 179:, 300–314, 2012.
RESEARCH IDEA
Applications of SfM photogrammetry in geoscience – Westoby, 2012*

9. Photo equipment
RTK-GPS
FIELD WORK
3D SCANNING
OFFICE WORK
3D MODELLING
123D Catch/ReCap (Autodesk)
CloudCompare
Matlab
DIGITAL ELEVATION MODEL (DEM)
TOOLS AND RESOURCES
Available tools and resources

10. One of research locations in Croatian-Japanese project „Risk identification and land-use planning for disaster
mitigation of landslides and floods in Croatia”
MOŠĆENIČKA DRAGA EXAMPLE
Mošćenička Draga – example of monitoring area

11. Investigation aims:
• Monitoring of steep to vertical slopes formed in talus breccias
• Application of SfM photogrammetry
• Possible landslide
• Possible landslide lake formation and debris flow
• Implementation of Mošdenička Draga Early warning System
LOCATION OF MONITORING AREA
Mošćenička Draga – example of monitoring area

12. 2012-11-05
2013-11-28
MONITORING PROCESS
Mošćenička Draga – two SfM 3D Point Clouds were compared

13. SEDIMENT ACCUMULATION
3d Point Cloud and x profiles (-15:5:+15)
profile 5
05-Nov-2012
28-Nov-2013
35
X profile 5
Sediment accumulation between y axis 11m and 21m
30
[m]
25
20
15
10
5
0
-15
-10
-5
0
5
10
profile 5
[m]
20
15
20
25
30
35
05-Nov-2012
28-Nov-2013
[m]
15
10
5
5
10
15
[m]
20
25

14. profile 15
35
X profile 15
Sediment erosion between y axis 11m and 21m
05-Nov-2012
28-Nov-2013
30
25
[m]
20
15
10
5
profile 15
0
12
-10
-5
0
5
10
15
20
05-Nov-2012
30
28-Nov-201335
25
[m]
11
10
9
[m]
8
7
6
5
4
3
4
6
8
10
[m]
12
14
16
SEDIMENT EROSION
3d Point Cloud and x profiles (-15:5:+15)

15. SEDIMENT ACCUMULATION
3d Point Cloud and x profiles (-15:5:+15)
profil 17.5
60
Y profile 20
55
Sediment accumulation between x axis 6m and 14m
50
45
40
[m]
profil 17.5
35
30
24
25
05-Nov-2012
28-Nov-2013
22
20
[m]
20
15
10
18
-30
-20
-10
0
10
20
30
[m]
16
05-Nov-2012
28-Nov-2013
14
12
2
4
6
8
10
[m]
12
14
16
18

16. COMPARISON
3d Point Cloud and x profiles (-15:5:+15)
Y profile 20
Good profile matching
profil 20
50
45
40
35
30
25
20
05-Nov-2012
28-Nov-2013
15
-25
-20
-15
-10
-5
0
5
10
15
20

17. EXAMPLES
Havišće – example of field and office work

18. EXAMPLES
Point cloud and profiles

19. EXAMPLES
Visualization and results

20. EXAMPLES
Visualization and results

21. Presented 3D point cloud derived from an image set has adequate quality for valuable use in
visualizing and quantifying slope morphological changes
• cloud density about 2000 points per square meter
• Standard ReCap 3D model mesh size is used (in order to get higher density it is possible to use even
higher mesh size)
• Ground Control Points – definition
This technique is convenient for frequent acquisition of high-resolution DEM at a fraction of the
time and cost of alternative approaches
One of the application of SfM photogrammetry method is monitoring of landslide movements
Possible as well in real-time landslide monitoring processes
CONCLUSIONS
Final remarks

22. THANK YOU FOR YOUR ATTENTION!
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