For those of you still using a compass, an easy to use website-
http://www.magnetic-declination.com/

That is interesting. What is really scary is that it immediately opened up with my location. Sometimes it scares me how much my computer and and various sites know about me.

Interesting...I should look at that more. When I flew in the 70'-80's, we were negative dec. around here. We're now positive by almost 11 degs in that time.
I don't bother with declination unless I'm out in featureless territory (ocean/big lake, deep woods) and neither of my favorite compasses are adjustable for declination. In fact, one has no markings at all except a N/S line. ;-)

GG, The site server reads your IP address and puts up the declination for where that is. Using my new GPS, I was able to see that the IP address location was a few miles up the road, probably at some switch somewhere in the system. My ISP is my phone company, so that's my guess. If you have cable, it's probably where the cable servers are, not your actual house address.

Frequenly those "geo-location" IP address things are off by a long way, so unless you can put it your *actual* location I wouldn't trust the answer you get. They're often going by the owners of netblocks and where companies are headquartered, etc. Sometimes they are very accurate and sometimes they are off by a *looooong* way.. (I have IP's in Edmonton that show up as being in Toronto in some of them..)

I'd take the results with a grain of salt. At my location the site returned 15deg 39min, the latest USGS topo (1989)says 17deg 30min and when I measured it last summer (compass transit pointed at Polaris)I got just under 20deg...

1989 is way out of date-that was 20 years ago, so the current dec sounds right to me.

This NOAA website is even better-
http://www.ngdc.noaa.gov/geomagmodels/struts/calcDeclination

You can set the year and see not only the dec for that year, but the rate of change as well, which isn't constant.

The dec in my GPS is from 1990 and it is decreasing at a rate of 5'W per year. In 1990 it was 14 and decreasing at only 1' per year.

Now my dec is 12 Deg 45', so it has changed by 1 Deg, 15' W in 20 years. The rate of change will also depend on where you are.

actually be careful I bet it's accurate!

that critter moves!

the results on the site for my area agree with the canadian govenment calculator - 16.5 degrees east. Now the interesting part is I remember being taught 23 degrees east when I was a young pup - sure enough, I type in the same lat/lon in 1978 and I get *ding* 23 degrees east.. it's moved that much!

This is one reason I prefer the compass in my GPS that points to true north.
Jim

My compass points true north. because I set the declination dial on it correctly.

Your GPS points whatever direction was true north at your lat/long when they programmed your software. It can be years out of date.. doesn't matter too much - but trust me, you're at the mercy of some bozo who coded up the declination.

I know where it is coming from. It just surprises me from time to time at how much information is available to others without me telling them. I also am kind of surprised from time to time when I order something on the phone and the person on the order desk asks if want that charged to the same card I used last time and do I want it shipped to the same address even though I have not given them that information. It is tied in to caller ID. Some of us old frogs just remember dial phones, typewriters, slide rules etc and from time to time we realize how much the world has changed in our life time.

phat
"Your GPS points whatever direction was true north at your lat/long when they programmed your software. It can be years out of date.. doesn't matter too much - but trust me, you're at the mercy of some bozo who coded up the declination."

I'm not sure of that Bob. I am about 100% sure that there is no magnetic flux gate in the GPS so it can only point to "grid north" unless its told to find "magnetic north, in which case it could be off for the reasons you state. It cannot sense magnetism.
Jim

Grumpgord
Sliderulers? Hey my slide ruler points true north fer sure. Got it right here partner...
jim

Hmm. indeed you're right.. Mea Culpa. I guess they don't have an electonic compass in them -

I suppose it's fun to watch the GPS people do their little turn in circles three times thing like a dog going to sleep to calibrate it. I should enjoy that more..

Or maybe I'm channelling Rancid Crabtree or Retch Sweeny now

phat

I took my GPS outside with compass set to True and walked due north and then held a magnet up to it and then turned the magnet and there was no change in the readout. I then set the GPS compass to mag and walked the same path and held the magnet up to it and there was no change. The Garmin Foretrex101 cannot sense magnetic flux, however when I set it to Mag it read 17, so I guess the "usr" setting would allow me to enter a magnetic deviation. 17 degrees is no longer accurate here. So why do you have to rotate the GPS to calibrate the compass?
Jim

Gord, I remember all that stuff. Had a slide rule in junior high school. Nerd tech at the time. Now my phone has far more computing power than the computer NASA had in the Apollo and moon landers. We could go on, but things have definitely changed.