I've wondered about this for most a year. I should have thought of
asking here long ago!

In Magellan track logs, I always get a *6<N> after the date, e.g. the
*64, *6B, and *61 in this sample:

$PMGNTRK,2116.686,N,15747.068,W,00028,M,155220.32, A,,150208*64
$PMGNTRK,2116.663,N,15747.070,W,00026,M,155244.33, A,,150208*6B
$PMGNTRK,2116.643,N,15747.072,W,00021,M,155258.33, A,,150208*61

They're pretty clearly hex numbers--all I've seen range from *60 to
*6F--but what do they mean?

Bart Mathias wrote:
> I've wondered about this for most a year. I should have thought of
> asking here long ago!
>
> In Magellan track logs, I always get a *6<N> after the date, e.g. the
> *64, *6B, and *61 in this sample:
>
> $PMGNTRK,2116.686,N,15747.068,W,00028,M,155220.32, A,,150208*64
> $PMGNTRK,2116.663,N,15747.070,W,00026,M,155244.33, A,,150208*6B
> $PMGNTRK,2116.643,N,15747.072,W,00021,M,155258.33, A,,150208*61
>
> They're pretty clearly hex numbers--all I've seen range from *60 to
> *6F--but what do they mean?

It is a checksum. I think the software will disregard the data if the
checksum is not right.

Jack

Jack Erbes wrote:
> Bart Mathias wrote:
>> I've wondered about this for most a year. I should have thought of
>> asking here long ago!
>>
>> In Magellan track logs, I always get a *6<N> after the date, e.g. the
>> *64, *6B, and *61 in this sample:
>>
>> $PMGNTRK,2116.686,N,15747.068,W,00028,M,155220.32, A,,150208*64
>> $PMGNTRK,2116.663,N,15747.070,W,00026,M,155244.33, A,,150208*6B
>> $PMGNTRK,2116.643,N,15747.072,W,00021,M,155258.33, A,,150208*61
>>
>> They're pretty clearly hex numbers--all I've seen range from *60 to
>> *6F--but what do they mean?
>
> It is a checksum. I think the software will disregard the data if the
> checksum is not right.
>
> Jack


All the details are here:

http://www.gpsinformation.org/dale/nmea.htm

Jack

Jack Erbes wrote:
> Jack Erbes wrote:
>> Bart Mathias wrote:
>>> [...]
>>> In Magellan track logs, I always get a *6<N> after the date, e.g. the
>>> *64 ... in this sample:
>>>
>>> $PMGNTRK,2116.686,N,15747.068,W,00028,M,155220.32, A,,150208*64
>>> ... what do they mean?
>> It is a checksum. I think the software will disregard the data if the
>> checksum is not right.
>>
>> Jack
>
>
> All the details are here:
>
> http://www.gpsinformation.org/dale/nmea.htm

Thank you. I hadn't even wondered about the "A,," part. Now I wonder if
that ever varies.

Bart Mathias wrote:
> Jack Erbes wrote:
>> Jack Erbes wrote:
>>> Bart Mathias wrote:
>>>> [...]
>>>> In Magellan track logs, I always get a *6<N> after the date, e.g. the
>>>> *64 ... in this sample:
>>>>
>>>> $PMGNTRK,2116.686,N,15747.068,W,00028,M,155220.32, A,,150208*64
>>>> ... what do they mean?
>>> It is a checksum. I think the software will disregard the data if the
>>> checksum is not right.
>>>
>>> Jack
>>
>>
>> All the details are here:
>>
>> http://www.gpsinformation.org/dale/nmea.htm
>
> Thank you. I hadn't even wondered about the "A,," part. Now I wonder if
> that ever varies.

That is a Magellan tracklog sentence, it is explained at the link:

"A tracklog on a Meridian is made up of propretary sentences that look like:

$PMGNTRK,4322.061,N,07948.473,W,00116,M,173949.42, A,,020602*67
$PMGNTRK,4322.058,N,07948.483,W,00090,M,174202.45, A,,020602*69.

where

TRK Tracklog
4322.071 Latitude
N North or South
07948.473 Longitude
W East or West
00116 Altitude
M Meters or Feet
173949.42 UTC time
A Active or Void
,, Track Name
020602 date
*67 checksum"

The "A" is used in quite a few (or all?) NMEA sentences and its meaning
is usually toggled between meanings to the effect of Active or Void,
Authentic or Valid, or similar meanings. A warning of sorts about the
quality of the data. The http://www.gpsinformation.org page has
virtually everything anyone would want to know about GPS on it in one
place of another.

Jack

Jack Erbes wrote:
> Bart Mathias wrote:
>> Jack Erbes wrote:
>>> Jack Erbes wrote:
>>>> Bart Mathias wrote:
>>>>> [...]
>>>>> In Magellan track logs, I always get a *6<N> after the date, e.g. the
>>>>> *64 ... in this sample:
>>>>>
>>>>> $PMGNTRK,2116.686,N,15747.068,W,00028,M,155220.32, A,,150208*64
>>>>> ... what do they mean?
>>>> It is a checksum. I think the software will disregard the data if the
>>>> checksum is not right.
>>>>
>>>> Jack
>>>
>>> All the details are here:
>>>
>>> http://www.gpsinformation.org/dale/nmea.htm
>> Thank you. I hadn't even wondered about the "A,," part. Now I wonder if
>> that ever varies.
>
> That is a Magellan tracklog sentence, it is explained at the link:
>
> "A tracklog on a Meridian is made up of propretary sentences that look like:
>
> $PMGNTRK,4322.061,N,07948.473,W,00116,M,173949.42, A,,020602*67
> $PMGNTRK,4322.058,N,07948.483,W,00090,M,174202.45, A,,020602*69.
>
> where
>
> TRK Tracklog
> 4322.071 Latitude
> N North or South
> 07948.473 Longitude
> W East or West
> 00116 Altitude
> M Meters or Feet
> 173949.42 UTC time
> A Active or Void
> ,, Track Name
> 020602 date
> *67 checksum"

Yes, it is specifically that part of the text that I was thanking your
for. Of course, all but "Active or Void," "Track Name," and "checksum"
were obvious to the naked eye.

My additional wonderment was due to my never seeing a "V" where the "A"
is, or anything but null for "Track Name." I do name my tracks when I
save them, but it shows only in the file name.

> The "A" is used in quite a few (or all?) NMEA sentences and its meaning
> is usually toggled between meanings to the effect of Active or Void,
> Authentic or Valid, or similar meanings. A warning of sorts about the
> quality of the data. The http://www.gpsinformation.org page has
> virtually everything anyone would want to know about GPS on it in one
> place of another.

They've changed their URL to www.gpsinformation.net/, but I thank you
for this second good source of info as well.

Bart