A Small Comparison between Suunto and iPhone Clinometers
Since some of us now have iPhones and have downloaded the
Clinometer application I thought that someone needs to compare the
iPhone to the Suunto clinometer. Today I took 14 measurements each
while sitting on my couch to a ceiling heating/AC vent. I then
measured my eye height, the ceiling height, and the distance from my
eyes to the tape measure hanging from the vent as a plumb bob. These
measurements were: ceiling height = 96”, height of the eyes = 38”, and
distance to the vent plum bob = 219”. I used the measurements to
calculate the angle I was trying to measure with the Suunto and
iPhone. Before taking my measurements I calibrated my iPhone
clinometer according to the instructions. I also had the following
settings: Fast approximation-on, Beep on lock-on, wait for lock
accuracy of + 0.1o- all the way to the left (+ 0.1o), disable auto-
lock-off, and 3D glass effect-on.
The first thing that I do in order to calculate the angle A was to
calculate the distance from my eye to the ceiling; 96”-38”= 58”.
Since Tan A = a/b, we can rearrange the equation to find A by dividing
both sides by Tan. Since 1/Tan =Arc Tan the equation is A = (a/b) Arc
Tan. Filling in this equation with the data we get A = (58/219) Arc
Tan or A = 14.8336707057. Taking signifiginte numbers in mind I am
going to say the angle is 14.8o. (Note: I calculated this after
gathering the data as not to influence the clinometer data)
Now for the clinometer data:
Suunto iPhone Suunto iPhone
15.5 15.2 14.5 15.4
15.0 14.9 15.0 15.2
15.0 15.1 14.5 15.2
15.0 14.1 14.5 15.1
15.0 15.0 14.5 15.7
15.0 15.2 15.0 15.5
14.5 15.1 14.5 15.2
The means were 14.8 and 15.1 for the Suunto and iPhone respectively
with standard deviation of 0.31 and 0.35.
The one thing I noticed in my raw data is with the Suunto my highest
and lowest angles were 15.5 and 14.5 whereas with the iPhone they were
15.7 and 14.1. I can think of at least two reasons why. 1) I have
more experience with the Suunto than I have with the iPhone and 2) the
Suunto has a line to help repeatly “hit” the same spot whereas the
iPhone you are just looking down one side of the phone.
I also noticed after calculating the angle (14.8) the Suunto average
was closer than the iPhone’s (14.8 vs. 15.1). Now is 0.3o difference
significant? Bob has more experience with the Suunto than I do and he
has stated in the past that can read it to the nearest ¼ o. I myself
can only read it to the nearest ½o. Given this I believe that a
difference of 0.3o is.
How can the iPhone be improved? If one would add a sighting device on
to the iPhone this could help “hit” the same spot repeatly. Obviously
this can not be same one that is used in the Suunto’s, looking through
it with an optical illusion. Maybe a tiny gun sighting built into the
volume and/or ringer buttons on the left side. I think someone
thought of this earlier. With the sight and practice I believe one
could the angle down to the nearest tenth of a degree. With the
Suunto one can only really estimate anything less than 1 degree.
Beth
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