One thousandth of a minute?

[Guest glenn95630]

I'm trying to 'track down' a 'small bit' of information. Since the coordinates on the cache web pages are given in degrees and minutes (to 3 decimals), I was wondering how far a hundredth and a thousandth of a minute is around Sacramento (38.6 degrees north). I did some calculations assuming the earth is a sphere with a circumference of 24,900 miles. I came up with...

0.01' of latitude = 61 feet

0.001' of latitude = 6.1 feet

and

0.01' of longitude = 48 feet

0.001' of longitude = 4.8 feet

 

Is this correct? I realize this isn't exactly a GPS Unit or software questions, but I wasn't sure where else to post it.

Glenn95630

[Guest Markwell]

Depends on your latitude...

 

Think about the globe and it's lat/lon lines (not a map, but a globe). The Longitude lines that span north pole to south pole (and tell you your east-west position) get closer as they get nearer the pole, eventually intersecting. Latitude lines that circle the globe east-west and tell you your north-south position are much more uniform.

 

Here's a chart that arffer posted that will tell you just how far it is between degrees and decimals or portions, etc., at any given latitude.

[Guest mcb]

That looks about correct. The GPS uses an elipsoid instead of a sphere but your calculations seem like a pretty good estimate. If you like you could down load a little freebie application from Mentor Software called foward inverse. Heres a link: http://www.mentorsoftwareinc.com/PRODUCTS/FWDINV.HTM

 

I have used the program and find it pretty useful. Give it a try. You can figure out distance for your Thousand of a minute pretty accurate here. The program support many formats and Datums.

 

mcb

[Guest bwolv]

Looks to me like your figures are as good as you can measure!

[Guest bwolv]

Oh! BTW, .001 minute of latitude is pretty much always equal to 6.1 feet all over the globe. I know there is an extremely small variance due to elipsoid, but too small to measure my most folks. The longitude is what changes by latitude.

[Guest Pote]

I'm sure you all have this bookmarked, but there is a nice foot to mile/nautical mile/meter/everything else conversion tool found here:

http://www.onlineconversion.com/length.htm

 

Oh, btw - great table, Markwell! :^)

[Guest Markwell]

quote:

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Originally posted by Pote:

Oh, btw - great table, Markwell! :^)

---

 

Thanks - but not mine. Arffer was the one that posted it (he and I seem to be running into each other a lot lately, but no one ever seems to see us at the same time...)

[Guest Kerry]

Which can effectively make 0.001' at that Lat of 7.7'

 

Cheers, Kerry.

 

[This message has been edited by Kerry (edited 09 September 2001).]