Ipod Touch

[ian mckenzie]

One free app you can get is a virtual spirit level, kinda cool. It got me thinking though... could someone write an app to make the Ipod Touch into a cave surveying instrument? Just strap it onto a laser distance finder...

Someday they will be cheap enough so anyone can afford one. But I bet Suuntos will never come down in price.

[Crockett]

It's called Theodolite Pro by Hunter Research and Technology LLC. There is a free version too. Recently tested accurate to within 1 degree compared to Suunto over 14 shots in cave. This was a casual test. I use Theodolite Pro in my work and at play. It is a most useful app.

[Evan G]

It's called Theodolite Pro by Hunter Research and Technology LLC. There is a free version too. Recently tested accurate to within 1 degree compared to Suunto over 14 shots in cave. This was a casual test. I use Theodolite Pro in my work and at play. It is a most useful app.

Wow! Thank you Crockett!

I love my Ipod touch they make a waterproof case for it too!

http://www.thepocketsolution.com/PSI-45 ... +Case.html

http://www.h2oaudio.com/

[rlboyce]

Dude!!! This may be cause enough for me to buy an iTouch! I was wondering if they've found a way to make one into an inclinometer, but it appears they have.

[LukeM]

While the Touch could definitely be used as an inclinometer I don't think you can turn it into a compass as it doesn't have the magnetometer that the iPhone 3GS has.

I also found this from the Theodolite developer:

As far as accuracy, please check the help documentation for more detail. The accelerometer readings (horizon, elevation) are extremely accurate, especially if you run the in-app calibration. These measurements are good to about a tenth of a degree. The magnetometer accuracy (bearing, azimuth) varies from location to location, whether you are indoors, near metal structures, etc. Theodolite is limited by whatever hardware accuracy the 3GS magnetometer is capable of in a given situation. You can tap the status icon near Theodolite's compass readout to get details on the accuracy. It can be as good as 2-5 degrees, or as poor as 20-30 degrees if there is interference. All apps have the same limits because the accuracy is ultimately dependent on hardware alone.

It sounds like the iPhone/iPod could make pretty good inclinometers anyway.

[ian mckenzie]

The magnetometer accuracy (bearing, azimuth) varies from location to location, whether you are indoors, near metal structures, etc.

Is that not the same limitation as any compass has, including Suunto?

[LukeM]

Except that a Suunto is calibrated to something like +/-.25 degrees while the Theodolite developer is claiming 2-5 degrees accuracy in the best case. Not sure how scientific he is being there, but that doesn't give me a lot of confidence in the device as a compass

[Crockett]

Except that a Suunto is calibrated to something like +/-.25 degrees while the Theodolite developer is claiming 2-5 degrees accuracy in the best case. Not sure how scientific he is being there, but that doesn't give me a lot of confidence in the device as a compass

The accuracy statement for the iPhone / Touch probably comes from some internal algorithm related to external (and maybe internal to the device) magnetic interference levels and not the capabilities of the sensor.

I know Suunto compasses are calibrated for inclination by zones of the earth, 'cause the box says so, but I was not aware of another calibration done by Suunto.

There are three obvious ways I can think of to compare a Suunto to an iPhone/Touch head to head: cave survey, run a loop, or run a compass course. I have surveyed with both and run them on my nearby compass course (with a known bearing to true north). I have not yet run a loop. This was not enough to draw a conclusion other than more testing would be worthwhile.

My gut is to go with what I know, the Suunto, but I want to know more.