Altitude accuracy in POLAR ‘S series ‘



VS1

New Member
Jun 6, 2005
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Hi,



In order to measure the grade at certain sections of a very (very) steep ‘service road’, I checked the LISTING file of the POLAR software and copied it to an excel spreadsheet.

Parameters are sampled every 5 sec. and I was dividing the ‘change in Altitude’ by the ‘change in distance’



Theoretically this should be the way to measure.. only there are sections there that the ratio over one sample is even higher then 50% !! (attached XLS spreadsheet).



Well this hill is indeed very steep – I climb with CX bike (CX tires) and use ring/cog 34/34 or 34/30 - lean forward and even when the road is dry, I feel some slidings at the rear wheel…!!



Altitude values are negative as the part of the place is below sea level



Does it make sense .. what can be the wrong things here.. ? Thanks!!





HR

spd

altitude

distance





Grade..!!

159
5.5
-70
14.678
4
-7
-57.14%
160
4.9
-68
14.685
2
-7
-28.57%
159
5.1
-67
14.692
1
-8
-12.50%
158
5.7
-66
14.7
1
-12
-8.33%
159
8.3
-64
14.712
2
-11
-18.18%
163
7.8
-62
14.723
2
-11
-18.18%
166
7.8
-58
14.734
4
-8
-50.00%
169
6.1
-55
14.742
3
-8
-37.50%
170
5.4
-53
14.75
2
-7
-28.57%
170
5.1
-52
14.757
1
-7
-14.29%
169
4.9
-50
14.764
2
-7
-28.57%
167
4.7
-50
14.771
0
-7
0.00%
166
4.8
-47
14.778
3
-7
-42.86%
165
5.2
-45
14.785
2
-8
-25.00%


 
I can tell you're probably having fun with this but, if all you want is % grade there is an easier way using the Polar software that is included with the units like the S725. On the altitude graph place two lap markers, one at the start of the grade you want to measer and a second at the end. Place the cursor over the second marker indicator and the % grade between the two points is listed in the data.
 
rodenmg said:
I can tell you're probably having fun with this but, if all you want is % grade there is an easier way using the Polar software that is included with the units like the S725. On the altitude graph place two lap markers, one at the start of the grade you want to measer and a second at the end. Place the cursor over the second marker indicator and the % grade between the two points is listed in the data.

well, that I know and this is one of the 2 ways I usually check the grades; the reason I went to the listing is that the ridden distance is quite small and when I done that with the right mouse on the graph and got 40something % I thought it's a mistake and went to see the list..

what I wonder is how accurate the polar is.. (S725 is what I have)
 
Set a longer time interval and you`ll get more accurate results. You got gradient for every 10 metres of the road while altitude is meassured by air pressure difference. It just can`t be that accurate.