OpenCPN

[Rhoel_Asia]

1 comment and 2 questions:
1 Comment: Highly impressed with this OS project - It took me a few minutes to figure out how to move from a wide area chart to coastal detail but found it relatively intuitively. I will look at the source code and see if I can contribute to the effort - part of my job is WebGIS programming.

Q1: I am unable to zoom out very far - I have my Guam charts loaded but cannot zoom out far enough to locate this sea area.
Q2: I have world shoreline and regional coastal vector charts in ERSI shapefile format. can I use these in OpenCPN, or convert to whatever is the base format of the vector charts OpenCPN uses.

Also, I'll charge up my GPS PDA and see if OpenCPN will run on WinCE 4 whatever. Be dead cool if it does.

I look forward to contributing to this great project.

Rhoel

[idpnd]

Super news.. I read just the other day that the NOAA had released their world shoreline database for free; a google earth overlay on the basis of local cache might be an option as well (the commercial package fugawi supports this). Dave has also got GRIB file support on the wanted features list over at sourceforge.

A1: If you are using raster charts, you may need to use the "scale in/out" buttons to switch to the appropriate chart for a particular scale.

[cagney]

idpnd

..they are the official government charts aren't they.

..yes they are, but with a limited scope. From the page you linked to:

...the EAHC is very pleased to accomplish this mission by producing small scale official Electronic Navigational Charts (ENC) of the South China

"Small scale" and "South China Sea" are the key words. Just look how the Philippine waters east of Palawan are treated, no info at all.

If you need official detailed charts from Hong Kong , the HK Hydrographic office are more than happy to sell you some ENC-cells.

From comparing other S-57 vector charts I draw the conclusion
that they are all produced with a built in max zoom.

Thomas

[idpnd]

I see, you're right. Btw I also experience "temperamental" hot key support (ubuntu/opencpn 1.3.1 from CVS).

[Rhoel_Asia]

Originally Posted by idpnd

A1: If you are using raster charts, you may need to use the "scale in/out" buttons to switch to the appropriate chart for a particular scale.

Nope these are vectored - I am using Bista :-( and the hotkeys are disabled too. I have another XP machine at work which I'll try tomorrow.

And thanks for the link to the NDDC Shoreline data - will follow up - the base map I currently have is the TM_WORLD_BORDERS-0.3 shapefile. Its a 6 meg file. U have checked it against my HR local Asia coastlines and find it pretty good - some small islands and rocks missing but definitely usable to get across oceans and arrive within visual site of your destination.

Rhoel

[sinbad7]

BEWARE!! The software when installed have a dozen or so faulty headers and missing files and in addition,all contains virus. CM93 ETC. INTENTIONAL??

[bdbcat]

All...

Regarding limited zoom-in for South China Sea ENCs:

The zoom-in limit is intentional in opencpn.

Background:
The South China Seas chart I looked at had a native compilation scale of 1/700,000. This generally may be interpreted as follows:

"The inherent accuracy of the chart is probably no better than 1.5mm at the compilation scale."
So, for 1/700,000 chart, this means that the chart accuracy is probably no better than (1.5 mm * 700,000) = 1050 meters.

Therefore, it is unwise and dangerous to use this chart at high zoom levels. Most industry analysts agree that anything greater than twice the compilation scale (i.e. 1/350,000) should be considered "over-zoomed".

Opencpn assumes the knowledgeable user will understand the dangers of overzoom, to a point, and allow overzoom to 4x the compilation scale, or 1/175,000 in this case.

The TrueScale value shown by opencpn is just that: the actual scale of the chart on your screen right now, accounting for different screen sizes and resolutions. Different displays will produce different values.

The fact that you cannot get closer than 1/346,000 on these charts is an artifact of the binary nature of scaling. Zooming in from 1/346,000 would give 1/173,000, which is more than 4x overzoomed (1/175,000).

Overzooming is an insidious danger with ECSs. It is all too easy to overzoom and assume the chart features are as rendered. This is especially true with vector charts, as the rendering remains as sharp as always. Overzoom is obvious with raster charts, as they become pixelated and blocky when so zoomed.

Think of it this way, in a paper chart analogy. Would you try to navigate with (1.5 mm / 4 = 0.015") (i.e. 4x overzoomed) accuracy on a paper chart of the entire South China Sea? Me neither.

Anyway, sorry for the long-winded diversion, but this is important.
For lots more on chart scales, overzoom, etc, see Nigel Calder's book
"How to Read a Nautical Chart"

School's out
Dave

[dacust]

Originally Posted by bdbcat

...
Overzooming is an insidious danger with ECSs. It is all too easy to overzoom and assume the chart features are as rendered. This is especially true with vector charts, as the rendering remains as sharp as always. Overzoom is obvious with raster charts, as they become pixelated and blocky when so zoomed.
...

@Dave, absolutely.

@ idpnd and Cagney: I need to separate out the coastal charts and the inland charts. That way the China charts will be more obvious on the page.

-dan

[phiggins]

For some reason I don't get notified when this thread is updated.

Dave re the WORLD.KAP it just hangs openCPN so I asummed a loop. This is under Vista. I'll check if it does it on XP.

[cagney]

Thank you Dave, for telling us how OpenCPN works regarding scales.
Is there a way to implement this zoom in limit for CM93 charts, once the largest scale chart is up, for a given location?

Look at these two screen shots, specially the TrueScale values.
I just pressed the "right arrow" key between the shots.
I'm using a version compiled 15 minutes ago from CVS.
Do you have any idea what's going on here?

Thomas

[idpnd]

Originally Posted by cagney

Thank you Dave, for telling us how OpenCPN works regarding scales.
Is there a way to implement this zoom in limit for CM93 charts, once the largest scale chart is up, for a given location?

I can zoom in to "truescale 0"; looking at locations I know, it would seem unrealistic to assume the charts are accurate to that degree.

Look at these two screen shots, specially the TrueScale values.
I just pressed the "right arrow" key between the shots.
I'm using a version compiled 15 minutes ago from CVS.
Do you have any idea what's going on here?

I get that exact effect (truescale apparently changing?) as well (yesterday's CVS).

[blubaju]

hm, when I click & hold the left mouse key and pull the map around the true value changes alltime, sometimes from 700900 to >4.7M within a few mm. winß version, regardless ENC or CM93

[cagney]

OpenCPN is fast and snappy out of the box.
But if you want it even faster, and don't want it slowed down by other processes doing their hose-keeping etc ??
I have tested two things that Linux easy let you do.
First give the OpenCPN process maximum "normal" priority:
$sudo nice --20 opencpn
Next step, full blast, give it real time priority:
$sudo chrt 99 opencpn

Confirm priority with: $top.
Both works nice for me, the last option definitely feels faster.
Give it a go! How is it working for you?
Any other ideas for breaking speed limits??

Thomas.

[blubaju]

Originally Posted by sinbad7

BEWARE!! The software when installed have a dozen or so faulty headers and missing files and in addition,all contains virus. CM93 ETC. INTENTIONAL??

1. Why you need other software when you have openCPN for free? Couriosity, I understand, I must try (almost) everything on my PC too

2. CM93 files, very unlikely as this is vector data only, no program. My AV (purchased) did not find anything, the data themself seem ok. For sure, feedback of the "brave" for intentional "bad" positions would be appreciated, regarding SE Asia I did not find anything wrong compared with NAVIONICS, same for the Northern Ardiatic Sea, Aegean Sea, Singapore and W-coast of Luzon (RP). As to my knowledge all CM93 "used" versions are from Russian origin.

3. Yes, when the black marks appeared I thought I'll give MaxSea 10 a try, then I got a keylogger warning. As I do not need it, I did not continue. This might be a danger, but I received similar warnings occasionally with legally purchased programs, very rare though.

4. Raymarine RNS, no need to install from this download, you can download it from Raymarine homepage as free planner and use the russkiss serial only, it works fine.

5. All other programs are very old, why bother about them

[sinbad7]

Bluebayou.. You are right,just curiosity.. I already have programs like Fugawi Marine Enc,OpenCPN,Seaclear and Shipplotter which are all doing a fine job. I am very impressed with OpenCPN's rendering of ENC maps and the virtually seamless transition from one area to another.

The AIS feature still needs some work to come up to the standard of other AIS capable programs. The target info displayed is very scarce and the screen still freezes up a little too often when loading maps alternate to CM93.
The ship icons could have different colors for quick type identification.
Using heavy data feeds via IP often immobilizes the program and is showing a great amount of falsely positioned AIS targets when zoomed out sufficiently.
I recently detected what I thought was a convoi of some 30 ships entering the Gulf of Aden. It turned out they belonged in the straits close to Copenhagen. Even a Copenhagen airport rescue boat was there.
I also miss being able to view a list of targets which are located within the geographical perimeters of the displayed map.

A great program when it is finished and has become more stabilized.