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Old 08-06-2013, 08:37   #1441
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Re: Feature Requests

Guys...
And looking especially at the latest tickets in flyspray, please, try to explain what you actually mean as we are not that good at reading minds and those 3-5 word descriptions are sometimes, how to say that, unclear...

Thank you

Pavel
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Old 15-06-2013, 23:41   #1442
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Re: Feature Requests

It seems to me it would be a good idea to have a 10m - 20m circle around the boat icon at high zoom to emphasize the limits of the GPS position data as represented on the chart., and perhaps a 100m circle at more moderate zoom.

It would also be give you a sense of the scale of the boat relative to surrounding hazards.

Maybe more work than it's worth. Just a though.
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Old 16-06-2013, 00:17   #1443
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Re: Feature Requests

A GPS today should give you a precision better than 2m 95% of the time, especially in an open sky environment like we have on boats, so I think that this does not make too much sense. but in the case that you need your system for dynamic positioning or automatic docking. Then one would work with Differential GPS and other sensors anyhow.
If you have worse values check your GPS (cablings, other antennas very close to it) or try one of the latest to see if the situation improves.

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Old 16-06-2013, 17:27   #1444
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Re: Feature Requests

Quote:
Originally Posted by bcn View Post
A GPS today should give you a precision better than 2m 95% of the time, especially in an open sky environment like we have on boats, so I think that this does not make too much sense. but in the case that you need your system for dynamic positioning or automatic docking. Then one would work with Differential GPS and other sensors anyhow.
If you have worse values check your GPS (cablings, other antennas very close to it) or try one of the latest to see if the situation improves.

bcn
dGPS and WAAS are great when you are within their operational areas and 2m/95% is reasonable there. What about outside the operational areas?

From my research of the issue, WAAS is limited to Alaska, Hawaii, CONUS, big chunks of Canada and Mexico and parts of the Caribbean. As you move away from these areas and the reference stations needed to determine corrections, accuracy falls off. By the time you get to Australia, Asia, Europe and Africa you are outside of Satellite coverage regardless of the level of improve offered by the corrections. WAAS is aiming for a 16m horizontal accuracy 95% of the time for aviation users (Table 3.2-1, pg20, http://www.gps.gov/technical/ps/2008...e-standard.pdf). Actual performance is 1.6m/95%nominal or 4m/95%Limit (I believe the difference is the limit is what should be expected and designed for and nominal is what is being observed currently) with 12m/max observed error (Table 3.3-1)


dGPS requires an appropriate additional receiver for the correction data. With the proliferation systems offered by various nations in different parts of the world it is not apparent that a single receiver will work with all systems currently operating or even a majority of them. Once again accuracy degrades with range from reference station. Some dGPS systems are proprietary and require paying a subscription for service during a specific period of time.

For straight GPS the DoD indicates a specified accuracy of 6.0-12.8m 95% of the time depending on age of almanac data (Table 3.4-1, pg 21, http://www.gps.gov/technical/ps/2008...e-standard.pdf)

Not mentioned in my first post was charting accuracy. In the US and Europe, the charts and the GPS coordinates agree pretty well. Elsewhere not so much. Even the in the US lets assume hazards are charted at the limits of WAAS (4m for 95% of hazards). If you encounter a hazard whose actual location is 4m closer than charted and you are really 4m towards the hazard than your GPS/WAAS is indicating then you are 8m closer to the hazard than the GPS indicates on the chart. Small fractions of time a hazard will be even closer. The Flinders Island tragedy shows that playing the odds doesn't always pay. (http://www.cyca.com.au/sysfile/downl...iry_Report.pdf)

In reality a lot of charting predates GPS, so errors will be significantly in excess of WAAS capabilities.

Having a reminder of the limits of technology would not be such a bad thing, a 10-20m ring will give you a sense of scale to potential errors with the GPS and the charting.
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Old 16-06-2013, 17:41   #1445
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Re: Feature Requests

Well...
The charts can be and sometimes are hundreds of meters off and don't contain all the dangers out there. The common sense and eyes should probably be your guide, not a 20m circle around the reported GPS position which tells nothing about any actual error be it position itself or the underlying chart.
It would take just a couple of minutes to implement, but I'm afraid all it will bring is a totally false feeling of safety as in "That rock is outside of that circle, I can't hit it".
Just my 2c

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Old 16-06-2013, 17:59   #1446
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Re: Feature Requests

So BCN argues that the GPS system is so good that we don't need to do anything and NOHAL argues that the charts are so bad it isn't worth doing anything about on this front.

I accept that things are really good in some areas and really bad in some others. I think that for the majority of people in the majority of locations outside the US a 10-20m circle would be a useful reminder to look outside the boat regularly and to consider the limits of the technology.

If no one has the time or interest to implement this fine, I certainly don't have the skills to do it myself. I just thought it would be useful for the less diligent but not stupid folks out there, of which I count myself.
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Old 16-06-2013, 18:26   #1447

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Re: Feature Requests

" a totally false feeling of safety as in "That rock is outside of that circle, I can't hit it"."

I think you have this opposite the more common perception, Pavel. Most of us will see the bigger blue circle and in fact say "I could be anywhere in where" as opposed to seeing a tiny blue dot and saying "I'm here". Good graphical presentations do not give the viewer a false accuracy, they should not say "You are here" when the truth is really "We know you are somewhere around here".

One of the few things that the sloppy kids at Google Maps have gotten right, is that they display a position circle which changes based on the system accuracy, rather than a tiny dot that ignores the "maybe you're somewhere in here".

If you ever look at the charts of stock prices, you'll see the same kind of bad information display--in each and every one of them. Rather than show the stock prices with a scale of, say, zero to 1500, they'll only show 1475-1525, so any minor fluctuation for the day looks like huge changes. That's just wrong, literally delusional, and when it is so easy to do better, why not?

Of course a really good information display might go one step further, displaying the position circle in red when the uncertainty was high (or the chart datum known to be suspect), changing perhaps to blue or green as the confidence was higher, as well as reducing the size of the circle.

There are some areas where GPS is known to be problematic. Or, the "standard" mapping is known not to conform to WGS. Oddly enough even in very well known places like New York City, where all the city mapping is still done to a Dutch New Amsterdam co-ordinate system within the city. Outsiders might never figure out why Google Maps sometimes gets street locations wrong by a half mile--so that's "red circle" territory, no matter how accurate the GPS numbers are.<G>

There seems to be a lot of odd stuff happening with GPS these days, which I personally suspect has to be coming from folks accidentally or intentionally creating local jamming. Sometimes, the toys just all go out to lunch. They never used to do that.
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Old 16-06-2013, 18:34   #1448
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Re: Feature Requests

Let aside that the functionality you ask for is actually achievable since I remember using radar rings (set it to something like 0.005 miles)
What I'm generally afraid of is not a sane user who is aware of the limitations and dangers of electronic navigation, but the one that thinks that the more he can zoom the vector chart the more accurate it is and passes a ten meter wide channel looking at the plotter screen instead of around the boat... I simply don't believe this functionality is either needed by the ones who know what they are doing or will educate the ones who don't.

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Old 17-06-2013, 01:37   #1449
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Re: Feature Requests

Just make your own experiment: connect the GPS when moored (fix, not swinging) and have a look on the plot after 24 or 48 hours. Take into account that the movement of the antenna due to roll will induce some track measured.
Modern GPS even without WAAS are pretty good. Especially in almost ideal conditions like on a boat. Open sky and slow moving vehicle.

This is however not an argument by any means to run a blind course looking at the screen. Just in the line of Pavel: I don't understand what a "possible error area reminder" might be good for.
In a small scale 1 pixel is bigger than 10m so you won't see it. In navigation where you are on a 1:7000 scale nobody of us argumenting here would rely just on the plotter. Or on the Radar.

It reminds me that type of disclaimers you find at every corner in order to avoid legal actions (not your intention, I know). And those do not make me sleep better or worse. I consider them as noise.

In order to keep the basic OpenCPN simple I would no like to see a feature like this - even if I might be able to disable it.

Hubert
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Old 17-06-2013, 01:47   #1450
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Re: Feature Requests

I'm with Pavel on this one. There are too many variables and a circle, or perhaps more accurately an ellipse, of whatever size is not going to remove the need for personal judgement and good seamanship. Just more clutter on screen ... ... ...
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Old 20-06-2013, 15:50   #1451
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Re: Feature Requests

I don't know if this has been mentioned before but I do have a suggestion. The box that shows the stats for the Current Leg of a route is totally unreadable for my tired old eyes. It's so small and the black background with the green numbers makes it even harder to read. I use these numbers all the time while under way. Even with a magnifying glass, it's hard for me to read. Chuck
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Old 20-06-2013, 19:56   #1452
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Re: Feature Requests

WaterwayGuy...

If I understand your request, I think you refer to the fonts in the Console, shown when you Activate a route.....

These fonts can be user adjusted.
Options->User Interface->Fonts->ConsoleValue

Have I got this right?

Thanks
Dave
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Old 21-06-2013, 06:31   #1453
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Re: Feature Requests

Dave, I think you are correct. I will try and adjust it today. Chuck
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Old 21-06-2013, 15:57   #1454
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Re: Feature Requests

Thanks Dave. That worked. The 6 point default is really small. you might consider 10 point for users like me that have a hard time drilling down in some of the menus. Chuck
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Old 26-06-2013, 13:20   #1455
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Re: Feature Requests

Hi Dave, I came to OpenCPN by way of CMap and Seaclear and have become a great fan of the program. All my cruising is done around the Australian coast and unfortunately we are not as blessed re freely available charts as are folks in the US or even our SE Asian neighbors. It appears from some of the posts I have been reading that some of our fellow seafarers would like to put the boat in the pen using the program (2m accuracy and dynamic range rings?) In the oilfields, with it's multi million dollar instrumentation systems we used a concept of an ellipse of uncertainty which was calculated in 3D and which stated that their was an xx% probability that the hole had penetrated a right plane within the ellipse. The term "probability" tended to restrain one from assuming absolutes of accuracy.

I notice on other forums that their is a lot of interest in running the program on some of the newly available small form computers such as Raspberry PI. This is of interest to those of us with limited power supplies who begrudge every milliamp. When I am motoring I do not have a problem with power usage however when sailing it becomes serious as there is a big draw, particularly with nav lights, autopilots, sails shading solar panels etc and zero recharge after dark.

It would be great if the program will run on some of these power miser, low cost, computers however failing that would it be possible to say add a small sub-program to allow the use a full resources computer for route planning then download the route to one of the limited resource but power miser boards running a hockey puck type GPS to transmit the SOG, COG, Distance to Waypoint etc data to the autopilot.
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