Lowrance Track Storage

[+user13371]

According to Lowrance's website, the iFinder H2O allows:

 

Up to 100 savable and retraceable plot trails, with up to 10,000 points in any trail

 

This suggests you could store 1,000,000 trail points in the unit's active memory. But it's not so.

 

First off, a trail can be defined to have up to 9,999 points, not 10,000. But more importantly, the real limit, based on internal memory and the amount of space each point requires to store, is only around 58,000 points. So Lowrance is overstating the iFinder's storage capability by a factor of 17 (1000000 / 58000).

 

Questions:

 

- Is this false advertising, even with the magical weasel words "up to" in their description?

 

- Will any users ever be impacted by this unadvertised limitation?

 

- If the answer to either of those questions is "NO," then why do we ever base buying decisions on advertised specs? The specs may be lies but we don't use the advertised capability anyhow

Edited November 17, 2005 by lee_rimar

[+Gener_Lee]

Up to 100 savable and retraceable plot trails, with up to 10,000 points in any trail

 

Call me a party Pooper, but all this means (to Me ). Is you can have up to 100 saved trails (if they are small ones) and any 1 trail can have up to 10,000 points.

 

Just me, but I would not assume this means that Every Trail can have 10,000 points.

 

and the 9,999 thing ... Well every ad will tend to round up to the nearest Whole and this only fudged 1 point ... lot better than 5 cents that most fudge

 

Anyway just my opinion

[+GOT GPS?]

Should be stated that it can store up to 100 smaller tracks, or several tracks at 10,000 points each.

 

Does this GPS store more Track points when you clear out the waypoints?

[+megamapper]

According to Lowrance's  website, the iFinder H2O allows:

 

Up to 100 savable and retraceable plot trails, with up to 10,000 points in any trail

 

This suggests you could store 1,000,000 trail points in the unit's active memory. 

 

I believe its actually 99 trails of 9,999 track points in each trail.

 

99 trails * 9,999 points = 989,901 track points.

 

Up to 100 means 99, and up to 10,000 means 9,999 points. Anyways, I am not going to get into hair splitting over 989901 and 1,000,000 points. LOL!

 

But it's not so.

 

First off, a trail can be defined to have up to 9,999 points, not 10,000.

 

  But more importantly, the real limit, based on internal memory and the amount of space each point requires to store, is only around 58,000 points.  So Lowrance is overstating the iFinder's storage capability by a factor of 17 (1000000 / 58000).

 

??? Where are you getting this 58,000 point limit and factor of 17 overstatement ??

 

 

If the GPS will store 989,901 points...

 

If we assume for a moment, that "up to" is inclusive (which it is not) then we get the following calculation.

 

10,000 points * 100 tracks = 1,000,000 points assumed.

9,999 points * 99 tracks = 989,901 total points actual.

 

1,000,000 - 989,901 = 10,099 points assumed overstated.

10,099 / 1,000,000 = 1.0099 % overstating assuming you are correct that the wording "up to" includes the value stated.

 

I'm confused? Please tell me where you get the 58,000 figure from?

 

 

My Current Track list in my GPS looks like:

RouteA . . . . . . . . . 8,730 track points

HardToReach. . . . . 1,887 track points

BeaufortTrail. . . . . 892 track points

BeaufortRDS. . . . . 4,345 track points

BeufortSpur . . . . . 5,297 track points

FranklinRDS . . . . . 46 track points

FranklinSpus. . . . . 62 track points

SatPath. . . . . . . . . 3,317 track points

=========================

. . . . . . . . . . . . . 24,576 track points

 

 

 

Questions:

 

- Is this false advertising, even with the magical weasel words "up to" in their description?

 

I would have to say no to this. "Up to" does not include the value.

 

- Will any users ever be impacted by this unadvertised limitation?

 

I probably will. But it's going to take me a few years to do it.

 

- If the answer to either of those questions is "NO," then why do we ever base buying decisions on advertised specs?  The specs may be lies but we don't use the advertised capability anyhow

 

Well, you are entitled to your opinion. My opinion is, "if the GPS fails to store the 989,901 points, then that would be false advertising". I've managed to fill 24,576 points so my GPS is mostly empty <GRIN>.

 

I spoze you actually believe the mass media news that you see on TV, and in the newspapers to be true as well. Well, the U.S. courts state that it is not illegal for news broadcasters to broadcast information that they know is untrue. This is documented here. Therefore the mass media is "allowed to lie to you". The news is classified as 'entertainment'.

 

Kindest Regards,

---- MegaMapper ----

[+user13371]

Where are you getting this 58,000 point limit and factor of 17 overstatement ? ... Please tell me where you get the 58,000 figure...

There is only 512K of RAM in the unit for storing track data. Each track point takes 9 bytes of storage. Comes out to a little over 58000 points, but there's also a little overhead for each trail data structure.

 

Overall, there's only 2 megabytes of internal memory for user data, divided into 4 blocks. 512K block for trail data, 512K for waypoints, 512K for routes, and 512K for icons/markers (waypoints stored without name or time data).

 

I'm 100% confident in that "9 bytes per track point" detail, as I've written software to encode/decode USR files. I'm only 99.5% sure about the 2Meg, 4 blocks of 512K limit. That info was provided to me by the same bloke who gave me the docs on the USR format. But I do not have a tech document to back me up.

 

Of course being able to offload to an SD card makes the internal memory limitation less of a problem - but the way they advertise the capabilities seems a bit odd.

Edited November 17, 2005 by lee_rimar

[+megamapper]

I'm 100% confident in that "9 bytes per track point" detail, as I've written software to encode/decode USR files.

 

That's a pretty big assumption. You are assuming that how the data is stored in a USR file, is how it will be represented inside the unit. I suspect this assumption is incorrect.

 

My Lowrance iFinder PhD GPS, does not store date / time / elevation in the track data. The PhD has an altimeter, but yet, when I look at the USR files being output, there is no altitude or time data included in the track.

 

So obviously, there is no room for storing altitude with the track inside the unit.

 

I therefore would not be so assuming "9 bytes per track point" representation you describe in the USR file, as how data is represented inside the unit.

 

Based on what I'm seeing, an "absolute track point" would store up in 5 bytes, with 2 bits being spare. A 'relative position' track point could be done in 1 to 2 bytes depending on the amount of distance between points.

 

When the GPS saves a usr file, it adds zeros for elevation, converts relative points back to absolute values, resulting in the size of the resulting USR file considerably.

 

  I'm only 99.5% sure about the 2Meg, 4 blocks of 512K limit.  That info was provided to me by the same bloke who gave me the docs on the USR format.  But I do not have a tech document to back me up.

 

Of course being able to offload to an SD card makes the internal memory limitation less of a problem - but the way they advertise the capabilities do strike me as a bit odd.

 

Even with all the possible ways the data can be compressed, the storage of only 2 MB is quite small, and I do not see how one could that much data in there.

 

If the unit had 3 MB internally, then things would calculate out alot better, and I could see the unit being able to store all that track data.

 

Regards,

---- MegaMapper ----

[+Redwoods Mtn Biker]

In my book, I said...

 

"The iFinder can hold approximately 53,000 track points, depending upon how much memory waypoints, routes and icons consume."

 

I got this info from John Galvin, a cartographer extraordinaire. John has never led me astray, and I'm willing to take him at his word. Maybe you should ask over at http://groups.yahoo.com/group/mapcreate_format/.

 

Rich Owings

www.MakeYourOwnMaps.com

www.GPStracklog.com

 

"We were desert mystics, my friends and I, poring over our maps as others do their holy books." - Edward Abbey

[+user13371]

Rich, we're working from the same source I didn't mention JG by name because he doesn't post in these forums. He was very helpful getting me the docs on the USR format and also told me the internal memory sizes of the iFinder series.

 

I came up with the "around 58,000" figure with a simple calculation; 512Kbytes div 9 bytes per point...

 

512 * 1024 / 9 = 58254.2222222...

 

but this doersn't take the actual overhead of track names and structure. I'm sure the more conservative number of 53,000 is closer than my original guesstimate.

 

BUT... you remarkled that it would depend on how many "depending upon how much memory waypoints, routes and icons consume." I was under the impression the block of memory set aside for tracks was independent of memory used for waypoints and other data.

 

I guess we'll have to wander back over to Yahoo group and ask him. or I could just drop him a line...

Edited November 18, 2005 by lee_rimar

[+user13371]

And the answer is ... I had the storage wrong. There's only 512K total for intenral memory and a max of approximtely 53,000 track allowed. This confirmed by recent email from John Galvin:

 

I deduced that the total user memory for waypoints, routes, icons and trails, is 512K bytes.  That's based on the fact that trails use 9 bytes per point and with no other user data present, the maximum number of total trail points, is ~53K.  There's probably some various other variables used by the system in the battery backed SRAM, in addition to the user data.  Even if you max out on waypoints, routes and icons, it doesn't really put much of a dent in the total storage available for trails.

 

To elaborate on trail storage a bit, it is technically true that you can have up to 100 trails, with up to 9999 points/trail.  The kicker is, that not all 100 trails can have 9999 points, since the total points distributed among all 100 trails, must be less than 53K.  Probably a better way to state the capacity would be to say that there are 53K total trail points allowed among all 100 trails, while no single trail can have more than 9999 points.

 

BTW the 53K number, I determined empirically by creating more and more trail points, until the iFinder didn't work anymore.  I don't remember precisely what the nature of the malfunction was, when exceeding the 53K point limit and I suppose that the limit may change slightly from one firmware version to another, or one iFinder model to another.

Edited November 18, 2005 by lee_rimar