Lake GPS ???

[NYBo]

Re: Lake GPS ???

A further problem with the proposed but not quite identified chart plotter than can somehow take advantage of knowing the instant lake level is how this data is provided. On every chart plotter that I have seen there is typically no way to enter any sort of offset to alter the presentation of the depths that will be shown on an electronic chart. The data on the electronic chart about water depth is static data. I have never seen any method in a chart plotter that would allow the operator to alter the presentation of depth data based on having entered some sort of offset from the chart datum value. Because of this, I do not see that there is any way to incorporate the instant lake level into the display of depth data from the chart. As I read the initial comment about this, it was suggested that some unspecified model of chart plotter that was perhaps made by Humminbird has this extremely unusual capability.

If there is a particular model of chart plotter, from Humminbird or any other vendor, in which it is possible for the operator to enter an offset to the library of electronic chart stored data about water depth so that the chart plotter presentation shows new and different values for the charted depths, I would like to know where to find this chart plotter and read more about it. As far as I know, there is no such chart plotter, at least not in my experience.

I have seen chart plotters in which the operator can modify the data presented in the display from the stored chart by selecting various options such as USA or International symbology for aids to navigation, and in which certain information contained in pre-defined tiers or layers can be turned on or off for display by the operator, but I have never seen an electronic chart and chart plotter in which all of the soundings in the chart can be changed on-the-fly to represent a new sounding based on some new water level. If such a chart plotter and such digital chart cartography exists, I would be very interested in hearing more about it.

AFAIK, the charts displayed by chartplotters are simply digitized versions of paper charts, and the depths are simply part of the chart graphic file. Of course a chartplotter/fishfinder can be set to display the chart with the actual depth as calculated by the built-in sonar on the same screen. Perhaps this is the cause of the confusion about the chartplotter being able to compensate for fluctuations in depth- it can't, but the sonar part does.

 

[The Woo Woo Kid]

Re: Lake GPS ???

Here's a you tube link showing how to " adjust " your chartplotter and it's charts to changing water levels. basically, he positions his boat over a chart contour line and then does a depth sounding, compares the two and adjusts via lakemaster's menu....voila! pretty slick.

Tips 'n Tricks 30: LakeMaster Charts for Humminbird Features - YouTube

so yea it can be done, easily, quickly and should be fairly accurate.

 

[The Woo Woo Kid]

Re: Lake GPS ?

Re: Lake GPS ?

The Federal Aviation Administration who operates the Wide Area Augmentation System publishes monthly reports, like this:

http://www.nstb.tc.faa.gov/reports/waaspan43.pdf

If you check the report you see that 99-percent of the time the Vertical Error in WAAS was about 1.9-meters, or six feet. It also notes that these statistics "are compiled only when all WAAS corrections (fast, long term, and ionospheric) for at least 4 satellites are available." That means the best-case situations. In the worst case the error was more like 8-meters or more than 50-feet in the vertical solution.

So the best case is you might know the lake level within about 6-feet. I boat on the Great Lakes, and a variation of 6-feet in Lake Level is something that occurs over about a 25-year period. There are real-time water level gauges throughout the Great Lakes, and you can get the actual water level referenced to chart datum with an update every five minutes from those gauges via a NOAA website. For an example, see

St. Clair River, Lake St. Clair and Detroit River Current Water Levels

The gauge resolution seems to be to about an inch or less. If I were worried about the water level, I would put much more faith in the data from a gauge, one that I could see myself or one that NOAA provides electronically, than I would ever put in the elevation from my GNSS position solution, even if in a precision fix with Wide Area Augmentation System enhancement.

I read an article from an independent tester who reported the WAAS enabled device was accurate vertically within 3 ft throughout their testing.

 

[NYBo]

Re: Lake GPS ???

Here's a you tube link showing how to " adjust " your chartplotter and it's charts to changing water levels. basically, he positions his boat over a chart contour line and then does a depth sounding, compares the two and adjusts via lakemaster's menu....voila! pretty slick.

Tips 'n Tricks 30: LakeMaster Charts for Humminbird Features - YouTube

so yea it can be done, easily, quickly and should be fairly accurate.

Well, I'll be darned! :facepalm:
That's some fancy stuff right there.

 

[jhebert]

Re: Lake GPS ???

Here's a you tube link showing how to " adjust " your chartplotter and it's charts to changing water levels....

That only works with the specific chart data and the specific plotter that was demonstrated. Also, the operator entered the offset based on his SONAR finding, not on a measurement of the altitude from the GNSS receiver. It is a nice feature for that particular chart and plotter.

The LAKEMASTER chart data appears to be closely associated with HUMMIBIRD. I can't recall seeing this feature on other chart plotters with other chart data. LAKEMASTER says:

"LakeMaster HD charts and patent pending technology are now available exclusively for use with Humminbird [chart plotters]."

It is a nice feature for that combination.

 

[jhebert]

Re: Lake GPS ?

Re: Lake GPS ?

I read an article from an independent tester who reported the WAAS enabled device was accurate vertically within 3 ft throughout their testing.

I just conducted my own independent test of the altitude measurement using my GPS receiver in a Lowrance HDS-8, without WAAS precision. Sitting on my bench, over the course of about three minutes, the altitude measurement varied over a range of more than 170-feet. I don't find that this is sufficiently precise to be useful for setting the level of a lake or other body of water whose level changes.

 

[RustynMtnHome]

Re: Lake GPS ?

Re: Lake GPS ?

And what was the topic of discussion here .....

 

[jhebert]

Re: Lake GPS ?

Re: Lake GPS ?

And what was the topic of discussion here .....

Please read the initial article in the thread to find the initial topic.

In general, I find that when people begin to change the topic of a discussion from the actual topic being discussed to a new discussion in which the topic is the discussion itself, the amount of useful information related to boating goes to zero. For this reason, I find that there is little value in postings in which someone tries to make the discussion itself the topic of discussion. This also goes for postings in which people try to make the other participants in the discussion the topic of the discussion.

 

[bruceb58]

Re: Lake GPS ???

In general, I find that when people begin to change the topic of a discussion from the actual topic

You mean where a poster starts scolding people on the proper terminology what they should be calling a "GPS"? You mean that type of changing the topic?

 

[QC]

Re: Lake GPS ???

Ahem . . . I find that there is good info here, and that it is on topic. Thank you.

 

[jhebert]

Re: Lake GPS ???

You mean where a poster starts scolding people on the proper terminology what they should be calling a "GPS"? You mean that type of changing the topic?

No. Using proper terminology is critical to conveying information. If incorrect terminology is used, only confusion results.

Scolding is given to anyone who uses the correct terminology and mentions the confusion and ambiguity created by using the wrong terminology. The person that does that is scolded by a dozen or more people who previously had not been participating in the discussion, but, apparently become enraged when the proper terminology is used. For these self-appointed moderators of forum decorum, there is apparently a rule that no one is ever to be told they are using the wrong terminology. If you don't believe me, just try using the proper terminology in a thread where the wrong terminology has been used. You will be scolded relentlessly.

What I mean by a discussion of the discussion, as we are having now, is when someone joins the discussion but offers nothing of value about the topic. Instead of staying on topic, they begin a new topic in which they want to have a discussion about the original discussion itself, or about the people in the discussion.

That is what is happening now. This fellow Rusty jumped into a nice discussion about GPS and charts and decided he would change the topic to start discussing the discussion. As I said, when this happens, the information value in the discussion goes to zero. Boating or electronics are no longer discussed, and in their place we have some silly discussion about who said what, was that the right way to have a discussion, and so on.

If you want to ruin a discussion, just change the topic to the discussion itself or the people in the discussion. That leads to a loss of boating or electronic content. That is why I suggest that people who don't have any information to add to the discussion should just sit on their hands, stay off the keyboard, and keep reading. If they don't like the discussion, they should go find another one to read. But joining the discussion to give your opinion about the discussion just leads to a lot of noise and a dilution of the information content. That's why I never scold people or talk about people or try to discuss the discussion. I really am only interested in boating electronics. I could care less if some bozo thinks the discussion is not very interesting.

 

[QC]

Re: Lake GPS ???

My post was supposed to be interpreted as stop. Please do.

 

[jhebert]

Re: Lake GPS ???

HUMMINBIRD and LAKEMASTER seem to have a lot synergy going with their exclusive chart data and chart plotter arrangement. The selection of a chart plotter now seems to bring with it a selection of what charts will be used, as several chart plotter makers are producing chart plotters that can use only their own brand of charts. I think that is the case with Garmin chart plotters, which use Garmin-branded charts, and now with Humminbird chart plotters that can use LakeMaster charts. As a result, if you want to use a chart plotter on a certain body of water, and you want to use a certain brand of charts, you are limited to a certain brand of chart plotter.

The lake-level offset adjustment available on the Humminbird devices is really a nice feature. If my boating were done on one of those impoundment lakes where the level goes up and down 30-feet or more seasonally, I think I would have a very strong preference for a chart plotter and chart cartography that could provide that feature. As I said earlier, I have not seen that feature before on any chart plotter. It might be an exclusive with Humminbird.