D/m/s Vs D/m.m

[nuhallid]

I'm new to geocaching but use GPS and GIS extensively at work. I use d/m/s in all my GPS units. I notice that most of the geocache sites in my area are listed using d/m.m. Any particular reason? My newest unit doesn/t (or maybe I haven't figured out how, yet) convert to d/m.m. It's no big deal to do it manually, but is there some reason for using that format instead of d/m/s?

[+Renegade Knight]

My GPS defaulted to DDD MM.MMM and WGS84 and as it happens those are what geocaching uses.

[+rusty_tlc]

I think it is a little more convient for non navigational types (me). Looking at maps I suspect that d/m/s would be easier to use to find your location using just a map and compass.

[+EraSeek]

I'm new to geocaching but use GPS and GIS extensively at work. I use d/m/s in all my GPS units. I notice that most of the geocache sites in my area are listed using d/m.m. Any particular reason? My newest unit doesn/t (or maybe I haven't figured out how, yet) convert to d/m.m. It's no big deal to do it manually, but is there some reason for using that format instead of d/m/s?

Mostly because that is the default setting most GPS units come with. Also I have never seen any unit which can switch to the other format. It is there in your menu setup somewhere.

[+Poindexter]

Seconds only have a resolution of about 100' unless your unit gives decimal seconds. Minutes carried out to the third decimal have a resolution of about 6'. For use plotting your position on a map, UTM is much easier to do with a simple roamer tool with the UTM grid on the map.

[+Melrose Plant]

Yeah, what Poindexter said. I wondered the same thing myself until I thought about it. Seconds are 1/60 of a minute, whereas were are working in 1/1000ths of a minute.

 

You know, there was a time in my life, not so long ago, when my nickname was Poindexter.

[+lazylightning]

I got a converter

 

http://www.mentorsoftwareinc.com/Freebie/FREE1198.HTM

 

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

clearly the degrees and whole minutes will be the same, so we

just need to do something to the seconds to make them the bit after the decimal

point of the minutes. ANd it's really simple. Divide the seconds by 60, then

add that to the minutes, rounding to three decimal places. Taking some

obvious examples to check our maths:

 

N00 00' 15.000 => 15.000 / 60 = 0.250 => N00 00.250

N00 00' 30.000 => 30.000 / 60 = 0.500 => N00 00.500

N00 00' 45.000 => 45.000 / 60 = 0.750 => N00 00.750

[+rusty_tlc]

Seconds only have a resolution of about 100' unless your unit gives decimal seconds. Minutes carried out to the third decimal have a resolution of about 6'. For use plotting your position on a map, UTM is much easier to do with a simple roamer tool with the UTM grid on the map.

Where? Degrees of longitude are constant in measure*. Not true for degrees of latitude. The closer to the poles the smaller the unit of distance that defines a degree of latitude.

 

*Not really but close enough, to be real acurate you must account for the bulge at the equator. Hey I resemble that remark.

[+Poindexter]

Where? Degrees of longitude are constant in measure*. Not true for degrees of latitude. The closer to the poles the smaller the unit of distance that defines a degree of latitude.

 

True, but you got your latitude's and longitude's mixed up, it's the other way around.

[dsandbro]

Where? Degrees of longitude are constant in measure*. Not true for degrees of latitude. The closer to the poles the smaller the unit of distance that defines a degree of latitude.

 

True, but you got your latitude's and longitude's mixed up, it's the other way around.

Longitude varies with the cosine of the latitude.

 

All these formulas are easy to set up in a spreadsheet.

[+rusty_tlc]

Where? Degrees of longitude are constant in measure*. Not true for degrees of latitude. The closer to the poles the smaller the unit of distance that defines a degree of latitude.

 

True, but you got your latitude's and longitude's mixed up, it's the other way around.

Doh!

[bnolan]

I'm new to geocaching but use GPS and GIS extensively at work. I use d/m/s in all my GPS units. I notice that most of the geocache sites in my area are listed using d/m.m. Any particular reason? My newest unit doesn/t (or maybe I haven't figured out how, yet) convert to d/m.m. It's no big deal to do it manually, but is there some reason for using that format instead of d/m/s?

 

 

Mostly because that is the default setting most GPS units come with. Also I have never seen any unit which can switch to the other format. It is there in your

menu setup somewhere.

 

all of the consumer grade GPSr units I am aware of can switch between D/M/S and D/M.m

 

Perhaps if you post what model units you are using, someone can tell you what menu setting to change.

[+EScout]

ddd.ddddd is more precise than

ddd mm.mmm which is more precise than

ddd mm ss.s which is more precise than

ddd mm ss which is the limit on some GPSrs

 

UTM is slightly more precise than ddd.ddddd in latitude, but possibly not more precise than ddd.ddddd in longitude, at much of the world's latitudes.

 

What this means is:

Use ddd mm.mmm which is plenty precise for our purposes, and have fun, and be happy.

Edited January 24, 2004 by EScout

[+Amazon Annie]

On my Sportrak Map I have the following options:

DEG/MIN.MM

DEG/MIN.MMM

DEG/MIN/SEC

DEG.DDDDD

 

I use the second option : DEG/MIN.MMM and I've found most of the caches (if the original posting of the coordinates is right)

[jimburns]

If you're interested in a closer inspection of these differences and playing easily with the differences between points at different latitudes, a more indepth, free tool can be found here: Geo Convert

 

Regards,

Edited January 26, 2004 by jimburns