Did you hear something fall off? Traditional Geocache
Did you hear something fall off?
-
Difficulty:
-
-
Terrain:
-
Size: 
(small)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
This cache is also located on the trail some of the local mountain bikers call Airplane and this is the reason it has this name. As many of you know Leominster State Forest is located more or less directly under the flight path to Logan Airport. Many times returning from a business trip or vacation I have been treated to a great view of Wachusett Mountain Ski Area and the surrounding area, on more than one occasion I have been able to pick out my own house.
As the aircraft are descending and beginning to make their approach to Boston lots of things are happening to the aircraft and occasionally as things are opened and closed and engines are being adjusted things don’t necessarily go exactly as planned. The location chosen for this cache is the spot where what appears to be a large piece of the engine cowling that fell into the woods from an aircraft I assume was heading into Logan. When you get to the large piece of aluminum the cache you seek is located about 40 feet away on a heading of 30 degrees and it is visible from some angles. It should be winter accessible as it is about 4 feet above the ground. This cache is the same as most of the other caches in LSF; the debris on the ground will hinder your access somewhat.
Official Disclaimer: Virtually all of my Leominster State Forest caches are placed while on a mountain bike ride, I ride to the general area and walk into the woods and place the cache. If you're bushwhacking more than about 100 feet you're either lost or doing it the hard way.
A not so short note on GPS accuracy. Any form of positional accuracy is typically defined by a number which is usually called the Circular Error Probability or CEP. The CEP is the number expressed in feet or meters that equals the radius of the circle that you are probably standing within 50% of the time based on the coordinates your GPS shows. The bad news is there is a 50% chance that you are outside of the circle. On a Garmin GPS the CEP is represented by the blue circle you see around your position icon so if the cache icon is within the blue circle when you find it the coordinates are essentially dead on regardless of what your “Distance to” says. It is also worth noting that the diameter of the blue circle is usually much larger than the +/- accuracy number shown on the display.
When I place my caches I usually use an external, powered antenna that generally gets my CEP down under 4 meters +/- after I let the unit average for 300 fixes or about 5 minutes. 4 meters +/- means that both coordinates could be high or low by as much as 4 meters or 13 feet and because +/- implies a radius this works out to an 8 meter or 26 foot diameter circle. What this means is that there is a 50% chance that the location for any particular cache is somewhere inside of a 8 meter diameter circle because Garmin uses this 50% number for consumer grade GPS accuracy CEP. When a second GPS or even the same GPS at a different time is used it will have a CEP or positional tolerance of maybe 8 or 9 meters +/- unless you put it down and let it settle for a few minutes. What this means is initially you can be anyplace inside of a 60 to 70 foot diameter circle for a given pair of coordinates with a 50% chance that you are outside of that circle. Tolerance stack-up is where this all really starts to become a problem, if the cache is actually on the eastern edge of my circular tolerance and your location is on the western edge of your circular tolerance it would appear that based on your numbers the cache is at least 75 feet or more away and the numbers are way off. Both of us believe that we are where we think we are but, the probability is that we are both wrong and we are likely to be wrong in different directions.
I welcome suggestions as to the accuracy of my numbers but please set your unit down and let it average for at least 5 minutes and then log the actual numbers.
The website link shown below has a great explanation on what to expect for GPS accuracy, his long term averaged numbers suggest that plus/minus 8 or 9 meters is about the best we can actually expect regardless of what the folks who market our GPS receivers say.
(visit link)
One more note, most GPS units do not have a built-in electronic compass they use a GPS compass when you stop moving, the unit very quickly loses its orientation and from your viewpoint the direction to the cache will bounce all over the place. This problem is exacerbated by the unit showing your position bouncing all over the place each time it takes a positional fix. The solution to this is to walk in a circle, with the track mode or breadcrumb mode on, around the suspected cache location to narrow your search area.
Additional Hints
(Decrypt)
Va n gerr