trying to get a sence of distance

[Brian,Lauren&Mom]

Hoping someone well versed in the math of coordinates might know this: How many feet are represented my one minute, or one second of longitude or latitude. In other words, If a coordinate was off by one second or minute on the W coordinate, how far off would it be in feet?

[egorny]

Should answer your question

http://www.nga.mil/MSISiteContent/StaticFi...ors/degree.html

 

Ed G

[Brian,Lauren&Mom]

Not sure it does, as I don't know what fraction of a degree one second is. I tried entering it as .00001 and he number was hundreds of thousands of feet. seems unlikely.

[PastorJon]

Not sure it does, as I don't know what fraction of a degree one second is. I tried entering it as .00001 and he number was hundreds of thousands of feet. seems unlikely.

 

60 minutes in a degree

60 seconds in a minute

[reef mapper]

A minute is 1/60 of a degree and a second is 1/60 of a minute. Just do the divisions to get decimal degrees. Note that a second of latitude is always the same ; a second of longitude gets shorter with distance from the equator.

[+twolpert]

The difference in the "size" of a degree of longitude is one reason to consider using UTM coordinates instead of lat/lon. Since UTM is based on 1000m squares, you can easily tell how far you are from a designated coordinate.

 

To see your current position in UTM, simply switch your unit to UTM. In order to make this useful, you must also know the UTM coordinates of your target waypoint. If you are caching, geocaching.com now gives the coordinates of the cache in UTM (see the fine print just under the degrees/decimal minutes coordinates near the top of the cache description). If it's a multi which requires intermediate waypoints, you will be able to view the intermediate coordinates on your unit once you have entered the waypoint. One downside to this is that you must switch back and forth between UTM and degrees/decimal minutes rather frequently. On the other hand, it's very easy to "do the math" to find out how far you are from your target.

 

UTM coordinates consist of an easting and a northing. These are distances in meters from an arbitrary origin (which depends on the datum and the UTM zone you are in). Unless you're also using a paper map, you don't care about the origin of this coordinate system. You only care about the difference between where you are and where you want to be. The easting increases as you move from west to east; the northing increases as you move from south to north.

 

For example, GCVH54 is located in zone 15S with an easting of 706964 and a northing of 4268852. This is written as 15S E 706964 N 4268852. If you are currently at E 706950 N 4268860, you need to go 14m east (706964-706950=14) and 8m south (4268852-4268860=-8) to reach the cache coordinates. And yes, if you want the straight line distance, you need to consult Pythagoras and your calculator.

[+DocDiTTo]

In Harrisburg, PA:

 

1 minute of latitude: 2025.41 yards

1 minute of Longitude: 1547.29 yards

 

1 Second of latitude is about 101.35 feet

1 second of longitude is about 77.43 feet

 

Since you're farther north, your longitude distances would be slightly smaller.

Edited June 26, 2008 by DocDiTTo

[John E Cache]

Hoping someone well versed in the math of coordinates might know this: How many feet are represented my one minute, or one second of longitude or latitude. In other words, If a coordinate was off by one second or minute on the W coordinate, how far off would it be in feet?

One minute of latitude along any Meridian is 1 nautical mile. One minute of longitude at the equator is also a nautical mile.

 

1 nautical mile = 1.150779 mile (statute)

 

http://en.wikipedia.org/wiki/Nautical_mile

[Brian,Lauren&Mom]

In Harrisburg, PA:

 

1 minute of latitude: 2025.41 yards

1 minute of Longitude: 1547.29 yards

 

1 Second of latitude is about 101.35 feet

1 second of longitude is about 77.43 feet

 

Since you're farther north, your longitude distances would be slightly smaller.

 

THANKS SO MUCH this is exactly what I was hoping for! Appreciate your assistance.

[+GPSlug]

In Harrisburg, PA:

 

1 minute of latitude: 2025.41 yards

1 minute of Longitude: 1547.29 yards

 

1 Second of latitude is about 101.35 feet

1 second of longitude is about 77.43 feet

 

Since you're farther north, your longitude distances would be slightly smaller.

1 minute(or second) of longitude = 1 minute(or second) of latitude * cos(your latitude)

(spherical approximation is close enough)

[+trainlove]

As any engineer should know, do your own work.

 

The Earth is approximately 4000 miles radius so the circumference is approximately 25000 miles, good enough for non-government work

 

There are 360 degrees in a circle so 1 degree is about 69 miles.

There are 60 minute parts of a degree so 1 Minute is 1.15 miles, also known as a nautical mile.

There are 60 secondary parts of a minute, so 1 Second is about 100 feet.

Many people think that Minutes and Seconds have something to do with time, no. It's just the Babylonian number system that we inherited and any surveying book will tell you that it's minute parts of, and secondary parts of...

 

Most GPS's can display DD.ddddd, DD MM.mmm and DD MM SS.s.

So for North/South digits, .00001 Degrees is about 4 feet, .001 Minute is about 6 feet, .1 Second is about 10 feet. Actually Magellan Meridians only show whole seconds .

 

If you are at 43 degrees North Latitude then East/West digits are reduced by the cosine of 43 degrees, or about 70%.

 

UTM coords, being a true orthogonal coord system, 1 unit is 1 meter North, or East, or West or South.

 

The circumference of the Earth at the equator is actually different from that through the poles, and there are many different circumferences through the poles. But the difference of some 22 miles makes less than an inch difference at these least significant digit back of the envelope calculations.

[geoprincesss]

Could you simplify that for NUVI owners?

Edited June 26, 2008 by geoprincesss

[+twolpert]

Bottom line is that those numbers roughly agree with the previous Harrisburg, PA post. There's a little more information here if you display coordinates in decimal degrees or minutes/decimal seconds. But the numbers fall pretty much into line with the preivous post, even though Harrisburg is a tad south of 43 degrees lattitude.

 

The explanation is good. Just be careful of the term "reduced by", which seems to imply subtraction. In fact, it is multiplication, as stated in the formula in the previous post.