Subject: Another RD 1000 test
Date: Mon, 5 Dec 2005 10:28:43 -0500
From: "Leverett, Bob" 

Hi Folks, 

Attached is another RD 1000 test. I had to stay indoors yesterday and so used the time to I conduct some simple tests as shown. These latest tests are consistent with other previous tests showing that small targets tend to be under-measured and large targets over-measured when at fairly close range (45 feet and under). The next set of measurements will be done over longer ranges. I suspect they will show basically the same trends as past long distance measurements have shown. If so, I should be able to come up with some generalized adjustments. In opposition to the results shown in this test, several months ago, I did do one set of measurements at 30 to 60 feet of a 4 inch wide target and got good results. 

At this point, the bottom line for me is that the RD 1000 is nowhere near reliable enough for use where accuracy within 2 or 3 percentage points is necessary. The RD 1000 is easy to use and is convenient and it does appear to have a window of acceptable accuracy, but outside that window, results are unreliable unless some tricky adjustment factors are applied. For example, I strongly suspect that with added modelings, the Grandfather tree's measurement will eventually drop by at least 50 cubes. Some of the other trees in the sample of modeled trunks that show skimpy volumes will go up slightly because of the understating of small diameter trend. Overall, the modeled trees are well within the ballpark, but not necessarily within the infield. 

Bob

Database Developer and Systems Analyst
Information Technologies

RD1000Test-12-4-2005

Subject: RE: Another RD 1000 test
From: Don C Bragg 
Date: Mon, 5 Dec 2005 13:32:49 -0600

I spoke with Bill Carr at the SAF National Meeting recently about the
RD1000. For those of you who don't know Bill, he is retired Forest Service
who acts as a "pitch-man" for Laser Technology. He had some interesting
observations on the testing of the RD1000 that may be relevant, and I will
try to send y'all the gist of this conversation...unfortunately, I have to
help send out a funding proposal this week, so it may be a few days before
I can put something together...

Don C. Bragg, Ph.D.
Research Forester
USDA Forest Service, Southern Research Station

Subject: RE: Another RD 1000 test
Date: Tue, 6 Dec 2005 08:45:29 -0500
From: "Leverett, Bob" 

Don,

Thanks. I look forward to his comments. If there is a way to make the instrument yield more reliable results, I'm all ears. While I'm unsure of what kinds of field situations the instrument was designed for, at this point, I fear that many compromises were made to get utility across the 3 main type of features offered by the instrument. Maybe Bill Carr can shed some light on that. For instance, from the standpoint of field forestry, the RD 1000 may be quite adequate for quick measurement of many relatively small, straight trees. I wouldn't presume to judge what is acceptable from that standpoint. By contrast, though, what often interests us in ENTS are single trees with large, highly irregular shapes. But regardless, I fear that two flaws will always make the instrument of limited value to us. For small targets at distances much over 100 feet, the scale cannot be contracted enough to measure the target. This limitation rules out accurate diameter measurements for the tall pines I've been modeling. For fairly close distances, the scale cannot be expanded enough to measure large targets. This requires that I change my location when taking measurements of the largest part of the tree as compared to higher up. This causes me to be continually shifting into different zones of accuracy and reliability. 

From the work done so far, the ideal distance from a medium-sized tree appears to be from about 65 to 95 feet. I've got fairly good results for targets in the 18 to 36-inch diameter range. However, more testing needs to be done. 

Bob