100 gps-measurement in alpine · faculty of sports an health sciences technische universität...

Technische Universität München Faculty of Sports an Health Sciences

GPS-Measurement in alpine

skiing – possibilities and limits

Andreas Huber

Karl-Heinz Waibel

Dr. Peter Spitzenpfeil

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Peter Spitzenpfeil Ankara 2013

Outline Description of race courses

and estimation of ground

reaction forces by GPS-Data

and Video

• Recording GPS-Data by

commercial device

calculating slope-

parameter

• Recording video (TV-

signal)

calculating time/speed

Comparative Study on the

usability of different GPS-

Devices

• „Long-distance“-

Experiment

– Garmin

– Smartphone

– GPS-device

• „Giant-Slalom“-

Experiment


• Search for possibilities to capture coordinates in alpine ski racing:

• Description of race courses

• Estimation of ground reaction forces by combining course setting data and intermediate times at the gates from video analysis

Introduction


Used Devices

• GPS-Device: FRWD

O400

• Video: TV-Signal

(VHS, DVD)


• Coordinates from GPS-Device: – North-South (m)

– East-West (m)

– Altitude (m)

– Accuracy: 0.5 m

Data (input)

• Videoanalysis:

– Time code (s) at the gates

– Accuracy: 0.02 s


Calculation (distances and slope angle)

• Distance between the gates

• Distance longitudinal

• Distance lateral

• Slope declination

Gate B

Gate A

Gate C

Distance

Lateral Distance

Longitudinal

Distance

2/2/

x

y

z


Calculation (radius and angles)

• Radius of the Circumcircle: – Gate

– P1 and P2: Half distance to the gate before and later

• Opening angle: – Angle: P1 , Gate, P2

• Curve angle: – Angle: P1 , CC, P2

M

Gate A

Gate C

Gate B

P1: half distance Gate A/ Gate B

P2: half distance Gate B/ Gate C

CC: center of circumcircle

Radius of turn Gate B

Opening angle Gate B

Curve angle Gate B


Calculation (times)

• Time for the gate B:

– Time between half of

the distances (t2-t1)

Gate A

Gate C

Gate B

tA: time at Gate A

tB: time at Gate B

tC: time at Gate C

t1: time between Gate A and Gate B

t2: time between Gate B and Gate C

2/)(2/)(12 ABABCB tttttttt

2/)( AC tt


• Velocity: distance at the circular arc divided by the time for the gate

• Radial Force:

• Radial Acceleration:

• Ground reaction force:

Calculation

GateBBBB trv /*

BBB rva /2

22

NR FFF

BBR rvmF /*2

Gz FFF

rvmFZ /2

)cos( gmFN


0,0

200,0

400,0

600,0

800,0

1000,0

1200,0

-100,0 -80,0 -60,0 -40,0 -20,0 0,0 20,0 40,0 60,0 80,0 100,0

Tore

Lauf_rohdaten

Geländeübergang

Geländeübergang

Geländeübergang

ZIEL

START

Chart

Chart of the race course with additional

markers (transitions, position of coaches,

position of timing,…)

Chart: Finish at (0;0), Gates evenly ditributed


Table of calculated parameters


GS: Men Women

No difference in mean acceleration

Maximum velocity

Maximum acceleration

No difference in velocity

Min = 23m

Min = 27m


SG: Men Women

Very high velocity (mean/ max) No difference in mean and max acceleration

Min


Course setting

Difference in course setting -> -> Difference in stress


Velocity Force Regulations

• High velocity:

– Course setting straight

– Slope declination medium flat

(after a steep section)

• High forces:

– Course setting narrow

– Slope declination steep

– Velocity medium

>3g in GS (>2.5g in SG)

average acceleration/ turn

• Regulations on material:

– Side cut

– Length

– Width


• Base for further discussions regarding the regulations of material and course settings to improve the safety.

• Big influence of aero dynamical drag in SG (and even in GS)

• Calculation of constraint forces (drag and friction) in a next step

• Enormous loading -> preparation of strength and endurance is of extreme importance for the athletes

Conclusion


Methods

„Long-distance“-Experiment

• „Sella Ronda“

• Time: ca. 7 h

• Distance: ca. 85 km

– Skiing/Lift: 55 km

– Bus: 30 km

• Ascending: 6.800 m

– 26 lifts

• Descending: 7.700 m

• Peak: 2.562 m

„Giant-Slalom“-Experiment

• GS-course

• 10 turns

• Time: ca. 32 s

• Distance: 350 m

• Descending: 100m

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Comparative Study

GPS-Watch

• Garmin

Forerunner 910XT

– 1 Hz

– +/- 3,66m

Smartphone

• Iphone 3

– 1 Hz

– +/- 5-10m

– iSki-Tracker

– Map to Snow

– Scout

GPS-Device

• 2D Datalogger

GPS-mouse

– 12 Hz

– +/- 1,5-2 m


Bus

skiing


Total Distance: 82,73 km

Time Moving : 7h 06min

Avg. Speed: 10,6 km/h

Max. Speed: 65,2 km/h

Altitude max.: 2.498 m

Altitude min: 1.196 m

Results: GPS-Device


Results: Garmin Forerunner 910XT

Data

Distance

[km]

Time

[hh:mm]

Vmax

[km/h]

VØ

[km/h]

altitude

min [m]

altitude

max [m]

altitude

diff. [m]

ascend

[m]

descend

[m]

1 85,78 07:06 58,3 12,1 1.036 2.211 1.175 6.568 7.601

2 82,74 07:06 58,8 11,6 1.141 2.639 1.498 7.137 7.660

3 85,4 07:06 56,8 12,3 1.091 2.321 1.572 6.229 7.959

4 82,94 07:06 72,7 11,7 1.089 2.608 1.519 7.154 7.666

5 87,07 07:06 64,5 12,2 1.058 2.479 1.421 7.056 7.833

6 85,92 07:06 61,9 12 1.288 2.683 1.395 7.089 7.706

Ø 84,98 62,2 11,9 1.117 2.490 1.430 6.872 7.738

SD 1,75 5,86 0,28 90,91 189,68 140,74 383,81 133,36

SD% 2,1 9,4 2,4 8,1 7,6 9,8 5,6 1,7



Route



Route

46,45

46,5

46,55

46,6

46,65

46,7

46,75

46,8

11,7 11,75 11,8 11,85 11,9 11,95 12

late

ral

longitidinal

lateral and longitudinal data

Uhr 1

Uhr 2

Uhr 3

Uhr 4

Uhr 5

Uhr 6

Uhr 7


Results: Smartphone

iSki-Tracker

Distance

[km]

Time

[hh:mm]

Vmax

[km/h]

VØ

[km/h]

altitude

min [m]

altitude

max [m]

ascend

[m] Lifts [n]

1 88,39 07:06 77 20 1.072 2.471 8.973 26

2 83,7 07:06 69 20 1.072 2.470 8.131 23

3 93,46 07:06 75 19 1.072 2.503 9.065 27

Ø 88,52 07:06 74 20 1.072 2.481 8.723 25

SD 3,99 0 3,40 0,47 0,00 15,33 420,29 1,70

SD% 4,5 0 4,6 2,4 0,0 0,6 4,8 6,7


iSkiTracker: Route


Results: Smartphone

MAPtoSNOW

Distance

[km]

Time

[hh:mm]

Vmax

[km/h]

VØ

[km/h]

Ascend

[m]

Descend

[m]

Asc-desc

diff [m]

Lifts

[n]

1 79,64 07:06 64,35 20,96 6.307 7.482 1.175 25

2 83,77 07:06 63,5 29,55 5.976 7.465 1.489 26

3 82,19 07:06 62,1 25,45 5.884 6.997 1.113 27

4 83,48 07:06 69 27,64 4.858 7.125 2.267 25

Ø 82 07:06 65 26 5.756 7.267 1.511 26

SD 1,63 0,00 2,59 3,20 541,94 211,24 459,16 0,83

SD% 2,0 4,0 12,4 9,4 2,9 30,4 3,2


Comparison GPS Device Garmin ISkiTraker Map to Snow

Ø distance

[km] 82,73 84,98 86,05 82,27

Ø time

[h:mm] 7:06 7:06 7:06 7:06

Ø ascend

[m] k. A. 6.872 k. A. 5.755

Ø descend

[m] k. A. 7.738 8.552 7.267

Ø asc-desc

[m] k. A. 866 k. A. 1.512

Ø altitude

diff. max-min [m] 1.302 1.430 1.409 k. A.

Ø Vmax

[km/h] 65,2 62,2 74 65

Ø Vmean

[km/h] 10,6 11,9 20 26


Total distance quite equal

Rough orientation possible

Altitude values very different

Speed verry different

Conclusion – Comparative Study


„Giant-Slalom“-Experiment

• GS-course

• 10 turns

• Time: ca. 32 s

• Distance: 350 m

• Descending: 100m


m0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 575

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Distance [m] 0 50 100 150 200 250 300

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start Gate1 Gate2 Gate3 Gate4 Gate5 Gate6 Gate7 Gate8 Gate9

Sp

ee

d [

km

/h]


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m0

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m0 7.5 15 22.5 30 37.5 45 52.5 60 67.5 75 82.5 90 97.5 105 112.5 120

m0

510

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m 0 50 100 150 200 250 300

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start Gate1 Gate2 Gate3 Gate4 Gate5 Gate6 Gate7 Gate8 Gate9

Lap time Distance Altitude Altitude Altitude Altitude V_GPS V_GPS V_GPS

MIN MAX AVG Delta MAX AVG Delta

[s] [m] [m] [m] [m] [m] [km/h] [km/h] [km/h]

12 Hz 32,81 346 1868,4 1966,2 1929,5 97,8 55,7 38,1 55,7

1 Hz 33,00 311 1868,9 1966,2 1930,6 97,3 54,4 37,8 54,4

Diff -0,19 35 -0,5 0 -1,09 0,5 1,3 0,3 1,3

Diff % -0,58 10,12 -0,03 0,00 -0,06 0,51 2,33 0,79 2,33

Results

For exact measurements of position and speed, high frequencies are necessary!


Thank you very

much for your

Attention

100 gps-measurement in alpine · faculty of sports an health sciences technische universität...

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