Category: General (page 2 of 2)
On December 21, 2005, Team Phoenix hosted the Cachers Haven VIGPS coin release party at Vancouver Island Brewery in Victoria.
The antique nickel coin features the vigps.com logo on one side, with the endangered Vancouver Island Marmot on the reverse.
Three hundred coins were minted by The Caching Place, and all sold out within 30 minutes.
If you missed the event, you didn’t get to see this cake.
Written by CandC
As I have found out, much to my surprise, there are many different measures of the same thing in use in the Nautical world. These measure can be confusing, but also a great way to make a geocache more interesting. I have found two sources of information that are particularly helpful, though some times contradictory: The Admiralty Manual of Navigation, by the U.K.’s Royal Navy and The American Practical Navigator, by the U.S. National Imagery and Mapping Agency and known sometimes as “Bowditch”.
Here’s how the units breakdown:
| Unit | Admiralty (U.K.) | Bowditch (U.S) | Note: |
| International nautical mile (nm) | 1852 m | 1852 m | US Dept of defence uses 6076.11549 ft with a yard to metre conversion of 1x=0.9144m exactly. (From Bowditch) |
| Geographical Mile | 1855.4 m | 6087.08 ft (1855.52 m) | The official definition of this unit is according to both sources “1 minute of arc along the equator.” The admiralty figure given here uses the 1924 spheroid. |
| US Survey Mile | N/A | 5280 ft(1609.5m) | Used on rivers and inland waterways. |
| Sea Mile | 1842.9 m at 0d 1852.3 m at 45d | Same as nautical mile | Defined by the admiralty as the length of 1 minute of arc of latitude. Figures are given for the 1924 spheroid. |
| Statute Mile | 1760 x, 5280 ft | N/A | Note this is the same as a US Survey mile. |
| Cable | Depends on Latitude (aprox. 200x) | 185.2 m | Defined by both the Admiralty and Bowditch as one tenth of a sea mile. Note that sea miles differ according to the source. The Admiralty points out that a cable is most often approximated as 200 yards. [Apparently, a cable once considered to be 120 fathoms] |
| Fathom | Not given | 6 ft (1.82898m) | |
| Shackle | [12.5 fathoms (22.862m)] | [15 fathoms 27.435m] | Neither of these measures is given by either source, however these measures are still used by mariners, to the best of my admittedly limited knowledge. |
Note:
- Figures in (round brackets) are my conversion and have been converted using 1ft=0.30483m.
- Text in square brackets is from The Sailor’s Illustrated Dictionary by Thompson Lenfestay, and is attributed to a particular country.
Geocaching enthuasiast CDMS was interviewed by David Grierson for an On The Island segment which aired on Tuesday February 17, 2004. This interview, which focused on Team KFWB / X-Treme GPS Team caches, is available for your listening pleasure thanks to the generosity of CBC Radio Victoria. Turn up your speakers, and click here.
Written by Plantman
I am certain we have all questioned the accuracy of our GPS at one time or another. This article provides details on how to determine the accuracy of your unit. This article explains how to test your unit if you live near, or are visiting Victoria.
Take your GPS unit to the top of Mt. Douglas. Beside the lookout there is a concrete pillar with a brass plate on it. This plate is an official geodetic survey reference point. The exact location of this point is 48 29 35.05139 X 123 20 48.28241 and the elevation is 225.073 m. This data is good to 0.001 m. The Mount Douglas geodetic location data is in degrees, minutes and seconds to 5 decimals. It requires a little arithmetic to get it into the more familiar geocaching format of degrees and minutes to 3 decimals. The accuracy of the equipment doesn’t justify more than 3 decimals. I make it 48 29.5842 X 123 20.8047 that you want to get within + or – 0.003. You should be using Map Datum WGS 84.
Lay your gps unit on the brass plate and turn it on and leave it there for 5 minutes then record the reading. You will not get exactly the same reading but you should be within + – 0.003 which is about 20 feet at this location.
You will not get it exact since there are some intrinsic errors in the whole process. One technical error source is how many and specifically which satellites are in view and take part in the calculation at any given time. The same machine will likely give a different reading on different dates. A more esoteric error source is the speed of light through the column of atmosphere under the particular conditions in effect that day. This is sensitive to the density of charged particles and thus to solar activity.
The arithmetic is Euclidian, however, post Newtonian, Einsteinian and Quantum physics are in effect. This cheap, handheld gps unit we all take for granted is actually a high tech toy.
