general gps cord's

[kangaroo]

Can anyone please confirm the correct way to enter the last three digits of the GPS coordinates. For example, you find 174 42 15 and 174 46 141. On the last one its clear you enter the minutes as 46.141 but what about the first one where we have only two digits. Do you add the zero before or after, i.e. 42.150 or 42.015?

[mjbnz]

Where from? it depends entirely on what the source of co-ordinates are...

I imagine that it's a case of '0 on the end' though.

[ags]

Are you sure that you haven't got degrees : minutes : seconds ?

[Papa Bear_Left]

It does, indeed, look like degrees minutes seconds.

There's 60 seconds in the minute (and 60 minutes in the degree), so you need to divide the seconds by 60 to get the decimal part of the minute.

e.g. in the above, 174 42 15 would be 174 42.(15/60) or 174 42.250

[kiwilegend]

Or simply change your GPS to be in D M S and enter the numbers as given - and then switch it back if so desired.

The best idea is not to take shortcuts - use proper punctuation to avoid ambiguity. And tell whoever is writing it like that to do so too.
If you miss a fishing rock - so what. If you send a rescue helicopter to the wrong place???
The other thing to make sure of is what datum it is in.

Write 172? 31.456' (WGS 84)
or 172? 45' 56" (NZGD 1949) - then you can't go wrong.

[evilC]

Hi Kangaroo

Just been looking at some of your earlier posts and it seems you've had some ongoing difficulty with getting your head around the different formats that are commonly used (in GPS receivers and elsewhere) for display of latitude and longitude. Just in case the earlier replies to this thread haven't fully explained it, I'm going to add some more information. Please excuse me if this is stuff you already understand!

First, this page has some information about the basic of what latitude and longitude is all about.

Then you can find a bit more detail here about different ways of writing latitude and longitudes (and how to convert between them if you want to do it the hard way).

The key point is that your latitude or longitude can be specified in a number of different ways (but all still pointing to the same place on the earth).

For example, 39.5° South is talking about being halfway between 39° South and 40° South. That is using the "decimal degrees" format which is likely to be shown on your GPS menu as something like "H D.D" (where H stands for "Hemisphere" (I think!) - i.e. N or S or E or W for North, South, East and West - and the D.D means that all the numbers are referring to degrees, including probably a decimal fraction of a degree (i.e. a part of degree given as digits after a decimal point).

Each degree can also be thought of instead as equivalent to 60 "minutes". In this case the 39.5° South could be written as 39° 30' South (where the ' symbol after the 30 means "minutes"). I.e. 39 degrees plus 30 minutes South of the equator. In this format the degrees will always be a whole number, and the minutes might have a fractional part also. For example, 39° 30.750' South means 39 degrees plus 30.750 minutes South. (This is the "standard format" for geocaching.com). On your GPS unit this display format appears as "H D M.M" or similar.

The third (and last) commonly used format is to use degrees, minutes *and* seconds. I.e. each latitude and longitude is given as three numbers, a whole "degree", a whole "minute", and then finally the "seconds" which in this case might also have a fractional part after a decimal point. In this format the 39° 30.750' South that I talked about in the previous paragraph would appear as 39° 30' 45.0" South. This means "39 degrees, 30 minutes, and 45.0 seconds south of the equator". This is the same as 39° 30.750' South because 3/4 of a minute (the .750 part) is the same as 45 seconds, because each "minute" is equivalent to 60 "seconds" (of arc). This last method of specifying your latitude and longitude is likely to appear on your GPS receiver menu as something like "H D M S.S".

As Kiwilegend noted, it helps if the correct punctuation is used to make it clear, by using a ° after the degrees part, a ' after the minutes part, and a " after the seconds. When these are not spelt out you can make an educated guess depending on the how the numbers are spaced out and if decimal points are present. If there are three distinct values given for each lat and long (probably separated by spaces or similar) then it is likely to be a position given in the full degreees, minutes and seconds format (H D M S.S). If there are just two numbers then it is likely to be the degrees and decimal minutes format (H D M.M) and if there is just one number (including probably a decimal place and extra digits after that) then it is probably a decimal degrees format (H D.D).

The format selected on your GPS receiver will determine how positions are displayed and also how you have to enter them. You can change between the different formats whenever you need to - just be sure you understand the differences! The reason you might find you cannot enter digits higher that 5 in some places is that you are putting a value into a minute or seconds field, and these can can't go past 60 (because 60 seconds is the same as one minute, and 60 minutes is the same as 1 degree).

Hope this helps. If it doesn't, well, just ignore everything I said! There is probably a much better description out there somewhere on the net but I couldn't find it!

Here endeth the lesson...

evilC

[kiwilegend]

where H stands for "Hemisphere" (I think!)

I imagined that it would be Heading.

Good explanation though. Perhaps it could be put into a FAQ somewhere?

[evilC]

where H stands for "Hemisphere" (I think!)

I imagined that it would be Heading.

In my book "heading" and "bearing" have very specific meanings that don't really work in this context. I had a quick look on Garmins page - you'd think this area must cause enough confusion for new GPS owners to warrant inclusion in their FAQ but it didn't seem to be.

Must also double check how my basic yellow etrex presents the different format options - the ones I've mentioned above were based on Kangaroo's earlier posts talking about what he sees on his gecko 201. So a FAQ type thing would probably be better if it had a more complete table showing how the different brands and models described those different options.

Good explanation though. Perhaps it could be put into a FAQ somewhere?

Thanks. My latent "wanna be a teacher" feelings started showing...

[evilC]

More....

http://www.easygps.com/help/dlg_edit_coordinates.htm seems to support "H = Hemisphere". That page might also help those that aren't familiar with this stuff to understand what is going on with the different formats.

My old yellow etrex uses the following to describe the three formats:

hddd.dddd?
hddd?mm.mmm'
hddd?mm'ss.s"

I assume other Garmin units are similar but perhaps there is more variation than I thought in this respect?

[kiwilegend]

I think that that naming system is pretty universal. I've seen it used in a lot of programs - and not seen anything else - apart from 'signed' degrees.

[rediguana]

If someone starts collecting things like this, we'll put it in the gps.org.nz knowledgebase that is under development

Also, lat/longs are not universal - as you can have lat/longs using GD49 and WGS84 for example. They certainly don't point to the same point on the earth as a few here will attest too - usually about 200m apart. It is assumed that most people are using WGS84 when talking about lat/long - certainly on these forums. Sometimes its good to make it clear.

[kangaroo]

i use the gd 49 now as it has the last two digits on the end
makes it easy for me to use, i know wgs 84 is 3 digits so thats cool.
soem of the gps marks i have are haywire for say hunters bank outa wellington, i click goto onthe geko and it's no where near where it is lol. unreal. im just going to find my own spots now and then build up my own data base for my boat. and any one that wants them.

[kiwilegend]

i use the gd 49 now as it has the last two digits on the end
makes it easy for me to use, i know wgs 84 is 3 digits so thats cool.

Huh???

[kangaroo]

172? 31.456' (WGS 84) <---3 digits
172? 45' 56" (NZGD 1949 <===two digits
now i know where i am, im happy

[kiwitonita]

Hi Kangaroo - note the different types of coordinate numbers:

WGS shown is degrees, minutes and decimals of minutes
GD '49 shown is degrees, minutes and seconds.

That's why there's 3 and 2 figures. Two of many different ways to show the same location. EvilC has a very good explanation above - it's really important to understand it for confident and safe navigation.