Objectives

© Uwe Kersting, 2008 


GONIOMETRY and VIDEOGRAMMETRY 

in (Sports) Biomechanics 

Objectives 

Center for Sensory-Motor Sensory Motor Interaction 

Anvendt Biomekanik 

Uwe Kersting – Lecture 03 - 2008 

• Basic working principles of goniometers 

• Considerations how to apply them 

• How to interpret data gained 

• Basic principles of photogrammetry 

• 2dimensional video technique 

• Discuss advantages and disadvantages 

• Apply both techniques in running (practice 

examples) 


Contents 

1. From movement to data – a general 

concept 

2. Goniometry: techniques & limitations 

3. Goniometer application 

4. Fundamentals of photogrammetry 

5. Planar kinematics 

6. Summary 

1 

2 

3 

1



Biomechanics 

Da Vinci: Mechanics is the paradise of 

mathematical sciences because by 

means of it one comes to the fruits of 

mathematics. (1452 – 1519) 

Hatze (1971): Biomechanics is the science, 

which studies structures and functions 

of biological systems using knowledge 

and methods of mathematics. 

Newton’s laws etc. 

Biomechanics = Science of the 

effects of forces on human body 

system 

• Movements of segments of interest 

• Muscles as the actuators 

-------- 

• Kinematics = movement of segments 

or total body 

• Kinetics = forces acting on segments 

or the total body 


A sport biomechanist‘s job 

or one possible way to go 

• Description 

• Analysis 

• Interpretation 

• Suggest a change 

• Re-evaluate 

• Teach / train the changes if 

effective 

How? 

4 

5 

6 

2


Sensor 



Goniometer essentials 

Goniometer: 

uniaxial 

‚parallax‘ 

multiaxial 

digital, analog 

Measurement chain 

Amplifier AD converter Computer Storage medium 

SIGNAL 

The digital frontier 

Figure 1: Measurement chain. 

software 

printer 

monitor 

Goniometer essentials 

Fulcrum of goniometer = fulcrum of 

joint! 

REPORT 

REPORT 

7 

8 

9 

3



Rearfoot goniometer 

Jumps in athletics 

Planar motions? – fundamentals of modelling + 

biomechanical accessability 

L1: TAKEOFF 

DISTANCE 

TAKEOFF 

ACCURACY 

v 


BODY 

POSITION 

Long jump analysis 

(i.e. partial distance model) 

TAKEOFF 

HEIGHT 

PHYSIQUE 

TAKEOFF 

SPEED 

DISTANCE 

L2: FLIGHT 

DISTANCE 

TAKEOFF 

ANGLE 

AIR 

RESISTANCE 

ACTIONS 

ON 

LANDING 

BODY 

POSITION 

L3: LANDING 

DISTANCE 

10 

11 

PHYSIQUE 

12 

4

v 


Biomechanical analysis... 




L1 L2 L3 

Technique analysis 

5 

We use models for 

- simplification 

- representation/mapping 

- reduction 

- subjectivation 

• Define phases of movement 

• Identify factors of importance 

• Identify criteria to assess techniques 

Historical perspective 

simple models 


Aristotle (384 - 322 B.C.) 

De Motu Animalum 

„If a man would walk in the sunshine in parallel 

to a wall the line, which his head describes 

would not move in a straight line. It would 

follow a zig-zag pattern; going down when he 

flexes and moving upwards when he 

straightens.“ 

13 

14 

15 

5



Measure directly or use images? 

Pros and cons? 


Technical realisation: 

camera obscura 

Also described and 

used by Aristotle, 

Kepler 

First technical 

drawings by 

Leonardo DaVinci 

(1490) 


b 

Improvements 

Optics of light beams, inclusion of lenses, 

photographic recording 

Focal length = „distance of lense centre to the 

location where incoming parallel beams cross“ 

For a standard photo camera (24 * 36 mm): f = 50 

mm represents a ‘normal’ view 

16 

17 

18 

6




Multiple exposure 

Eadweard Muybridge 

(1830 – 1904) 

Multiple exposure & viewpoints 

Central plane 

Object 

Image 

Central plane 

Object 

19 

20 

Image 

21 

7




Caution! - on two levels 

‚Fish eye-effect‘ 

Caution! - on two levels 

‚Waterfall-effect‘ 

Lens correction 

Freeze! 

22 

23 

24 

8

Braune and Fischer 

(~ 1900) 

Scaling the on the 

imaging plane 




Simpler approach 

is possible 

Examples of sports techniques 

Pole vault 

Example II, choice of perspective! 

25 

26 

27 

9


Partial heights 

model 

(transferable 

to many 

movements) 

(Hay, 1978) 



Example III 

H 

Use a model 

Partial heights model: factors 

28 

29 

30 

10



Summary 

Aim of biomechanical investigation 

is to: 

describe movement and explain how 

it works 

reduce trial and error approaches 

in coaching and teaching. 

There are obvious limitations 

There are big advantages 

Optics 

How to measure the size of an object on an image? 


Calibration for 2D 

Reference measurement (calibration) 

If the movement plane is parallel to the 

imaging plane a distance measure is 

sufficient to calibrate the set-up. 

If the movement plane is aligned 

obliquely we need a 4-point 

calibration. Common digitisation 

software includes this option. 

31 

32 

33 

11

Limitation of 2D 

analyses to planar 

motion and correct 

camera positioning 

...?... 


Alignment 

Example: Track and Field - Side view 

Camera on the stands 



e 

γ 

τ 

δ + τ = β 

δ 

Track 

34 

35 

36 

12


Cinematography 

24 images per second 

(std.) 

Low cam – 800 images 

per second 

Mechanical shutter 

1/10 000 s 

- lighting! 

‘by hand’ digitisation 


Limitation: 

25 or 50 Hz 

time 

resolution 


Video technique 

Image construction out of lines 

Camera chip 

digital 

Video 

Video technique 

Digitisation; frame grabber board 

1 

2 

3 

4 

5 

6 . 

7 . 

12 3 4 5 6 7 . . . 

Video image 

analog 

Video 

37 

38 

39 

13


Recording on tape 

Video resolutions: in time: 50/60 Hz 

180 – 600 lines 

Electronic shutters 

Frame grabber boards 

< 512 * < 512 

Digital cameras – recording to tape or disk 

‚Megapixel‘ Images 

1024 * 1024 

Vicon MX = 4 Mpixel 



Rules for practice 

• Use 2D for one-plane motions 

• Align properly 

• Have athletes wearing suitable clothes 

• Use markers if possible 

• Use longest possible focal length 

• Use shortest possible exposure time 

• Adjust lighting 

• Make sure all the movement gets covered, 

but don‘t waste image area 

Summary 

Goniometers allow continuous recording of 

joint angles (1D + 2D) – reference 

measurement required 

Photographic techniques allow for a 

quantification of kinematic 

characteristics. 

Basic optical principles were applied to 

estimate limitations. 

One-plane motion can be quantified from in 

plane and out of plane camera positions. 

40 

41 

42 

14

Objectives

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