How Far Is .00001?

[+Old Bet]

For National Map Corps projects, I have to work in decimal degrees, such as N41.12345, W073.54321

 

As my Merigold averages, the extreme right-side digit fluctuates. It's close enough for government work, but I'm wondering how those fluctuations translate into distance?

I know horizontal varies with latitude (I'm at N41, W73) so can any one tell me, or tell me where to find a calcultor, for:

 

The difference, in feet, between:

N41.12345 and N41.12346

W073.98765 and W073.98766

 

Thanks

[+Old Bill]

This link should help....You'll need to do some calculator work to get it down to the 5 decimal place, but is doable.

 

http://pollux.nss.nima.mil/calc/degree.html

 

From your example of 41.12345° in lattitude, there is 275,518 ft in one degree of longitude. Breaking it down further we get this..... (and someone please correct me if I'm wrong on this....)

 

.1°=27,551.8 ft

.01°=2,755.18 ft

.001°=275.518 ft

.0001°=27.5518 ft

.00001°=2.75518 ft

 

I seriously doubt your GPSr is getting that kind of accuracy. That is, of course, unless you have a seriously high end survey grade GPSr.

Edited September 23, 2005 by Old Bill

[+Old Bet]

Thanks, Old Bill...

 

No, I am not that accurate.

 

In reality the numbers wander by several digits, and often it is both the fourth and fifth numbers that waver.

 

But I was curious how the changes relate to distance on the ground, and you gave me the answer.

[+Bob Blaylock]

  A degree of latitude is sixty nautical miles.  (A nautical mile is defined as being the distance subtended by a minute of angle (1/60 of a degree) across the Earth's radius.)  A degree of longitude is sixty nautical miles at the equator, but is less and less as you change latitude toward the poles.

 

  So .00001 of a degree of latitude is .006 of a nautical mile, or 3 feet, 7+3/4 inches.

Edited September 23, 2005 by Bob Blaylock

[WH]

Actually, distance between degrees of latitude decrease the closer to the poles you get. At 90 degrees N longitude, I can literally walk 180 degrees of latitude in just a couple steps. This distance is largest at the equator.

[peter]

Actually, distance between degrees of latitude decrease the closer to the poles you get. At 90 degrees N longitude, I can literally walk 180 degrees of latitude in just a couple steps.

I think you may have fallen on your side and are looking at the world rather askew - especially when you think of the pole as being at 90° N *longitude*.

[+geognerd]

OBB, remember, we are gathering coordinates for structures. You may also just want to walk and keep an eye on how much the decimal degree read out changes. Equate the change with your footsteps. Considering the size of most structures, it won't matter if the coordinates are off by a few steps.

[WH]

Im an idot. Please don't mind me.

Edited September 25, 2005 by WH

[peter]

The circles of latitude get smaller the closer to the pole you are while the line of longitude remain the same length.

Which doesn't support your previous statements at all:

Actually, distance between degrees of latitude decrease the closer to the poles you get.

 

Wrong. The distance you need to travel to go one degree of latitude is about 60 nautical miles no matter where you are (with slight variations due to the elliptical rather than spherical shape). So going from 0° latitude to 1° latitude is about 60 nm and going from 89° to 90° latitude is also about 60 nm.

 

At 90 degrees N longitude, I can literally walk 180 degrees of latitude in just a couple steps.

 

Wrong. There's no such thing as 90° N longitude - the north pole is at 90° N latitude.

Your statements consistently reversed the two. Changing latitude by 180° would require you to travel from the north pole to the south pole, i.e. +90° to -90°.