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TOPIC: Nikon Prostaff 550
http://groups.google.com/group/entstrees/browse_thread/thread/4cba36d0f02a1d9d?hl=en
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== 1 of 5 ==
Date: Sat, Aug 23 2008 8:12 am
From: bob leverett

ENTS,
On Thursday I bought a Nikon Prostaff 550 as a replacement for my aging Nikon Prostaff 440 - a workhorse unit that has served me extremely well, especially in those circumstances where clutter got in the way of a canopy or trunk shot. I used the opportunity of the purchase to test the current set of lasers I own against one another and against the ultimate arbiter, the tape measure.
The following two tables give the results of a set of 28 tests, the first 15 tests include tape measure distances and the latter 13 do not. As you can see in the table results, the Nikon Prostaff performed very well. Its measurements are virtually unbaised around a 0 difference between laser measured and taped distances. By contrast, my TruPulse 360 shows an inclination to slightly undershoot the target. This is consistent with past tests. However, the standard deviation computed for the differences is smallest for my TruPulse 360, so overall, it is the most accurate where targets are distinct and highly visible. My TruPulse 200 is the second most accurate, with my new Nikon 550 coming in third. The value of the Nikon is that it "sees" through small openings and can reach more illusive targets.
Sadly, my older two lasers (Busnell 800 and Nikon Prostaff 440) are showing their ages, but still very functional. The relative performacies/accuracies of these lasers are factored into a re-measurement of the Jake Swamp White Pine, which I also did on Thursday, as a prelude to Will's November 1st climb. The re-measurement that I did on Thursday will be the subject of my next e-mail accompanied by the proper fanfare. Please stay tuned.
Bob

== 2 of 5 ==
Date: Sat, Aug 23 2008 8:55 am
From: DON BERTOLETTE


Bob-
Thinking about submitting test to Consumer Reports?
Was the high reflectivity of the license plate due to the reflective 'tags'?
Plastic role? How do you ascertain level with the tape measure?
-DonRB

== 3 of 5 ==
Date: Sat, Aug 23 2008 10:07 am
From: dbhguru@comcast.net

Don,

When hanging free, the tape measure follows a curve called a concatenary. Laying the tape on a fairly level surface so that a measure between two points can be obtained without the tape sag and then holding the tape off ground so that the concatenary form is applicable allows me to make small adjustments. Its not absolutely accurate, but very close.

I've not done the level of testing needed for the Consumer Report. Too much work. However, the gradual accumulation of smaller test runs could eventually serve that purpose. I'm more interested in providing an intermediate level of analysis for the ENTS list. I also will write an article for the next publication of Brother Bragg's exemplary "Bulletin of the Eastern native Tree Society".

Below is an update of the last laser comparison table. It includes 6 more tests for the set of 5 lasers added to what was previously done where the standard was the tape measure.

BTW, at present Monica's and my bed is getting crowded. Snuggling 5 lasers at night can create a bit of congestion (they do get cold, you know and start to whimper). The rest of you do snuggle your equipment, don't you? Uh, everybody does don't they? Uh Oh!
On a more serious theme, my next level of testing will be decidely more sophisticated. I plan to devise some tests to compare laser performance under the less ideal circumstances we routinely encounter, e.g. measuring distances to indistinct targets like leafy twigs, ends of limbs and branches, etc. Let's face it, most of our targets in ENTS are of that type, not too many reflective road signs at the tops of twigs on broad-crowned hardwoods these days.
Oh yes, to answer your question. I think the excellent across the board performance of the lasers for the license plate was because of the reflective paint on the tag and its flat surface. I'm sure you expected that.

Bob
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== 4 of 5 ==
Date: Sat, Aug 23 2008 2:30 pm
From: DON BERTOLETTE


Bob-
Re concatenary, I can tell you have been here before...my exposure to 'manual' distance measurement goes back to the days working for a surveyor, as worked my way through college.

When working for the BLM in Eastern Oregon doing original corner restoration, we used the same model of mountain transit with four (?) inch compass, a steel "topo trailer" tape that was used in conjunction with a "topo abney". We repaired them in the field when they broke, and used tape pullers (kind of like brass knuckles) and a spring scale to properly "pull" the tape. We were looking for accuracy in the hundredths to tenths of a foot (surveyors measured in hundredths of a foot, it was crudely said back then that only architects and whores measured in inches...).

Later, working for land surveyors prior to electronic distance measuring, we used temperature correction (Central Valley of California gets rather hot!) in addition to spring scales to get the order of accuracy we sought. Using a three hundred foot steel tape took about all the strength the average man/strong women could muster on a full pull.

Of course later, we used electronic distance metering (my first experience was using a Hewlett Packard EDM that was about the size of an old typewriter case, and weighed about the same...not fun when surveying remote terrain. For long shots, a triple (triangular array of three parabolic reflectors), or a triple triple (nine reflectors) was used.

Your laser hypsometers don't yet match the old HP EDM for accuracy but sure beat the weight freight. But the lasers are more accurate (with high reflectivity target) than a rag tape, either on the flat (one guy measuring), or on 'concatenary' (with two pulling) with no control of pull strength.

I'm thinking your supposition is that the lasers accuracy approaches the flat or concatenary rag tape (rag covers an array of flexible tape materials, including fiberglass) accuracy. I think that is probably reasonable...that said, with your penchant for measurements to a standard that allows you to stand righteous in the face of any challengers, I would expect continued honing in on the right balance between accuracy, cost to user, and dependability.

Re THIS Oct/Nov, I will be visiting/revisiting sites of known concentrations of five needle pines (foxtail, bristlecone, whitebark, limber, sugar, western white). I'm thinking of a paper/photo essay coming out of it, but look forward to putting myself where they are (subalpine Sierra Nevada/Marble Mtn./Trinity Alps wildernesses.

Re snuggling, if listen closely on a very quiet night, you may here the Opti-logic laser I had access too, seeking a new snuggler...so sad!
-DonRB

== 5 of 5 ==
Date: Sat, Aug 23 2008 2:49 pm
From: dbhguru@comcast.net

Don,

Good discussion and suggestions. Thanks.

Bob