Ed- "sight, drop it down, sight again, do you come up with the same readings"--(Huh!)
That's way James Brown, but I'll try it again-- I think they are both accurate. Steve On Wed, Jan 6, 2010 at 12:18 AM, Edward Frank <[email protected]> wrote: > Steve > > As far as I know nobody has ever compared the two here in ENTS. Brunton > makes top of the line compasses/clinometers for geology work. would thin > they would make good clinometers. The thing to check would be how easily > the readings are to take, how closely can you estimate the angle, and if you > sight the same point several times from the same position (sight, drop it > down, sight again, do you come up with the same readings. > > You can test the accuracy of the clinometer calibration: > > Ed Frank wrote (Sept 14, 2005) > http://www.nativetreesociety.org/measure/instrumentation/suunto_clinometer_testing.htm > > You can test the level accuracy of a clinometer or instrument. Sight from a > marked height at some object- tree of pole at a distance. Have an assistant > mark the point on the distant object the clinometer or instrument says is > level. Move to that spot and sight back to your original position. If it > is perfectly accurate the backsight will be right on the point you shot > from > originally. If it is reading high, then the angle it is off will be > under-reading by arc tan [1/2 (error)/distance]. If it is pointing lower > than the starting point, then it is reading high, calculations are the > same. > In this way you can tell at least if the original level line is actually > level or not. > There is no reason to think that the Brunton would be calibration error > would be any different from that of the Suunto. But you can use this > process above to develop a correction factor if you want. The error in the > clinometer is a simple mechanical one relating to the weight placement on > the dial. It is a simple error that should be exactly the same amount in > the same direction at all angles, unlike systematic errors which increase > over a range. However unless the clinometer is really way off, several > degrees, then the errors at the bottom (slightly larger but shorter > distances, ad the errors at the top slight ly smaller but longer distances) > tend to pretty much cancel out > > John Eicholz wrote (Nov 6, 2003) > http://www.nativetreesociety.org/measure/instrumentation/calibration.htm > I think I can prove mathematically that the error in tree height that > results from each degree of clinometer error is approximately between > 1.75% and 1.9% of the horizontal distance to the trunk...Because the > factor: (1/cos(@))*(Sin(@)-sin(@+e)) is nearly a constant! Its range is > a smooth progression from 1.74% at 0 degrees to 1.9% at 80 degrees. > > Ed Frank > > http://nature-web-network.blogspot.com/ > http://primalforests.ning.com/ > http://www.facebook.com/profile.php?ref=profile&id=709156957 > > ----- Original Message ----- > *From:* Steve Galehouse > *To:* [email protected] > *Sent:* Tuesday, January 05, 2010 11:09 PM > *Subject:* Re: [ENTS] Suunto vs. iPhone > > I have, and have been using, a Brunton clinometer rather than a > Suunto---any appreciable differences in quality or accuracy? > > Steve > > http://nature-web-network.blogspot.com/ > http://primalforests.ning.com/ > http://www.facebook.com/profile.php?ref=profile&id=709156957 > > -- > Eastern Native Tree Society http://www.nativetreesociety.org > Send email to [email protected] > Visit this group at http://groups.google.com/group/entstrees?hl=en > To unsubscribe send email to > [email protected]<entstrees%[email protected]> > >
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