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How far is a second?


dibbg

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Posted

Take look at this.

 

http://calgary.rasc.ca/latlong.htm

 

For latitude, it's basically the same everywhere. But for longitude, it changes with the latitude.

Latitude At the Equator (0°):

1° of Latitude (1/360th of the Earth's Polar circumference) is 110.5743 Km (68.70768 miles)

1' (1 minute) of Latitude (1/60th of 1°) is 1.8429 Km (1.1451 miles)

1" (1 second) of Latitude (1/3600th of 1°) is only 30.7151 m (100.771 feet)

0.1" (1/10th second) of Latitude (1/36000th of 1°) is only 3.07151 m (10.0771 feet)

 

Latitude At the Poles (90°):

1° of Latitude (1/360th of the Earth's Polar circumference) is 111.6939 Km (69.40337 miles)

1' (1 minute) of Latitude (1/60th of 1°) is 1.8616 Km (1.1567 miles)

1" (1 second) of Latitude (1/3600th of 1°) is only 31.0261 m (101.792 feet)

0.1" (1/10th second) of Latitude (1/36000th of 1°) is only 3.10261 m (10.1792 feet)

 

Longitude At the Equator (0° latitude):

1° of Longitude (1/360th of the Earth's equatorial circumference) is 111.3195 Km (69.17073 miles)

1' (1 minute) of Longitude (1/60th of 1°) is 1.8553 Km (1.1528 miles)1" (1 second) of Longitude (1/3600th of 1°) is only 30.9221 m (101.45 feet)

0.1" (1/10th second) of Longitude (1/36000th of 1°) is only 3.09221 m (10.145 feet)

 

Longitude At the Poles (90° latitude):

At the Poles - all lines of Longitude converge to a point - there is no distance between them.

You can go through all lines of Longitude just by turning around in a circle without going any distance.

Therefore, at the Poles there is no distance between longitudes.

 

Longitude At Other Latitudes:

At other Latitudes, the distance between longitudes decreases the further North (or South) you go.

Posted

 

Nice link, thanks for the information.

 

It does explain one thing that I figured out on my own, but I wasn't sure why. It was that when I walked slowly the GPS didn't update my position, or when it did, it acted "strange" (even when I walked in a straight line)

 

I found that if I run or walk fast it would give me better coordinates, and now I guess I know why.

Posted

Just to be clear:

 

DD° MM' SS" is not the same as DD° MM.mmm'

 

The former is a one second of longitude or latitude. The latter is one thousandth of a minute of longitude or latitude.

 

One second equals about 16.6 thousandths of a minute. That means here in South Carolina at about 34° 51' N, using Markswell's nifty table, one second east or west equals about 83 feet. Which answers the question the OP actually asked, but maybe didn't intend, and which also explains why Google Earth resolves DMS coordinates to hundredths of a second.

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