Understanding the GPS coordintes in the fishing books

[beefy]

Having recently got myself an old boat, I'm studying the fishfinder manual like mad. These are indeed great tools not only for fishing but also for navigating dodgy areas like Westernport.

I've got the map and books on fishing Westernport and Port Philip Bay. Here's an example of GPS coordinate from the map:

S 38 15 905 E 145 16 795

My Humminbird has three different ways of displaying GPS coordinates. From the user guide:

dd.ddddd°
dd°mm.mmm'
dd°mm'ss

The coordinate display used in the map/books appears to be closest to dd°mm'ss (degrees, minutes, seconds).
However, where I'm a little uncertain is in the last 3 digits of the south and east numbers.
There's only 60 seconds in a minute yet if the last three digits are indeed seconds then what does 905 and 795 mean.

Or is the 2nd format being used dd°mm.mmm' and is S 38 15 905 actually meaning S 38 15.905

I've been Googling for over an hour but cannot find examples of GPS coordinates written like they are in the map/books.

Is anyone able to educate me ?

[Sebb]

I can't remember, but I did the same thing. Found a website conversion. Something like GPS coordinates google map conversion, and it shows where it is on Google Map.

[beefy]

Thanks Sebb.

I've been looking at some of those but cannot find one that shows this exact format for entry.

After some more Googling I'm fairly confident the format of the three numbers are DEGREES MINUTES DECIMAL (of the minutes), or the DDM format (degrees and decimal minutes).

If that's the case, putting the minutes and decimal numbers together as a single decimal point number representing minutes would be so much more obvious. No idea why they are separated.

Anyway I think I need to choose dd°mm.mmm' from the Humminbird position format options. Phew

[ben475]

yep. degrees and decimal minutes.

google maps shows up in decimal degrees.

so many different formats, its easy to get confused.

[re-tyred]

You can change it in Google map setting. The format shown above is deg. Min.decimal min. That is the most common one used. The have just been lazy and not put the degree symbol and decimal point in.
S 38° 15.905 E 145° 16 .795

[beefy]

Thanks very much lads, great to have my thoughts confirmed.

[Sebb]

I put exactly what re-tyred types on Google with the ° and it came up.