Raster Charts or Vector Charts - Which is Best for Electronic Navigation ?

[Alecadi]

I'm wondering which type of charts is best with any navigation software?
Should I use only vector Charts?

Thanks

[Surveyor]

You should not limit yourself to just one type. Vector charts are derived from paper charts and NTMs. Raster are scanned paper of course. Both are only as good (ie fresh) as the version of the chart and up to whatever date of the NTMs that affect it. It is a PITA updating raster charts with NTMs. The brand of your vector charts will determine how fresh they are and how often they are updated.

THE best is paper IMHO. Buy the latest and edit them by hand with the NTMs. You will always have the latest and greatest. If you have to have electronic charts, your probably going to have to go with both raster and vector due to weaknesses/errors in both in different areas of the world.

[belizesailor]

Originally Posted by Surveyor

You should not limit yourself to just one type. Vector charts are derived from paper charts and NTMs. Raster are scanned paper of course. Both are only as good (ie fresh) as the version of the chart and up to whatever date of the NTMs that affect it. It is a PITA updating raster charts with NTMs. The brand of your vector charts will determine how fresh they are and how often they are updated.

THE best is paper IMHO. Buy the latest and edit them by hand with the NTMs. You will always have the latest and greatest. If you have to have electronic charts, your probably going to have to go with both raster and vector due to weaknesses/errors in both in different areas of the world.

+1.

Use whichever is most accurate for the areas you plan to cruise. You will of course be limited by the technology you are using to display them.

Always have paper chart back ups aboard.

[cal40john]

So far I haven't made extensive use of electronic charts. What I have done is Garmin Bluecharts (vector) on my portable 76cx and NOAAs raster charts on Seaclear on a netbook.

One claim of vector over raster is that the text remains the same size as you zoom in or out. Don't know if this is a problem with other software, but as you zoom in and out details come and go to keep the clutter on the screen reasonable. You can set how much clutter you want, but even at the max information setting I've found information at a lower zoom level (bigger chart area) that disappears at a higher zoom level. I never can figure out what zoom level I need to be at to find the chart information I want.

Also physical landmarks are much fewer on the vector charts. When I'm trying to orient myself visually to double check I've had problems relating what I'm seeing on the vector chart to the landmasses around me. I think it's partially due to the small screen size, but one time I was zooming in and out trying to make sense of the islands around me and I couldn't relate what I was seeing to the chart. My little boat on the chart said I was headed for an area that was ok to travel through. I stopped the boat picked up the paper charts, which allowed me to orient myself and discovered that while where I was heading was actually safe it wasn't a short cut on the wrong side of a buoy that I would normally have taken just based on the paper chart. I followed the longer route that I would have taken based on paper.

The raster charts are easier for me to find information, but that is probably due to familiarity. I don't use the raster charts as much because the netbook lives below, and Salish Sea sailing is mostly visual DR on the spot at the helm nav.

John

[tamicatana]

I was in graphics in the print biz for 20 years, and I don't think the technology is any different for this.

Vector is a drawn image, like as in Illustrator, similar to CAD. Vector is infinitely sizable, regardless of file size.

Raster is a pixelated image, ergo a scanned image/TIFF/GIF/JPEG etc, and thus physical size and resolution are inversely related. That is to say, as one sizes up, the resolution goes down, and vice versa. Your detail is limited to the file size, and if you want to enlarge beyond the limits of the scanned file, you have to rescan to get a bigger file or else you get interpolation (bitmapping/pixelating). Of course, since we view maps on tiny screens at 72ppi, the file sizes don't have to be so large to still hold good detail.

The vector files will hold detail at all view enlargements... but someone has to go in and physically digitally redraw the charts, I expect that's how they're done.

[Alecadi]

thanks to all
and by the way, I ALWAYS have paper chart on board. ALWAYS.

[osirissail]

The vector versus raster nautical charts is an old question. As stated by others, raster nautical charts are simply scans of real paper charts or the acetate originals. As such, the chart files take up a lot of memory.

Vector nautical charts are considerably smaller in memory/storage size so a lot more maps can be stored in a chart plotters memory. But to get smaller file size, a lot of the "nice" and sometimes critical details are left off the vector chart. Although the newest vectors have gotten much better at retaining the details of the original chart.

But - #1 - your chart display system - Chart Plotter or PC computer system will determine which type of charts you can utilize. Small chart plotters do not have the storage memory to handle raster charts so normally are only vector.

PC computer-type systems normally have large file storage capabilities so can utilize raster -and- vector. Check out Sea Clear II and OpenCPN for free charting systems that can use most any type chart, including some you make yourself.

Personal preference then determines whether you like the visual style of a classical nautical chart or can make due with a vector display. I would say that these days both vector and raster are equal in presenting the important nautical information you need to navigate with safely.

[Jon Hacking]

Another nice thing about vector charts is that your display software should know that depths are depths, & what units they're in & how you like them displayed. MaxSea always displays depths as meters, but OpenCPN respects your settings & will display depths (from vector charts only) in whatever units you select. Also, vector charts display all the text right side up, no matter what orientation you have the chart in.

There's also a tremendous size difference. A copy of the CM93 world charts (vector format) takes up ~1.4GB, or about 2 CDs. 2 CDs of Raster charts covers about half of the eastern Caribbean.

But as folks have said, why limit yourself? Go ahead & get both. Most respectable navigation programs will display several different chart formats. We use OpenCPN & have several different chart formats loaded.

[SailFastTri]

Originally Posted by tamif27

snip

The vector files will hold detail at all view enlargements... but someone has to go in and physically digitally redraw the charts, I expect that's how they're done.

MISLEADING! That little bit of mis-information can and will sink your boat. It's technically correct because the "file" will hold the detail, but detail will not be displayed on-screen at all zoom levels. All chart view software will remove detail at zoomed-out levels so hazards such as charted wrecks, rocks and reefs/shoals will not be displayed. When using vector charts to set up a route on-screen it's imperative you zoom in to display full detail and then pan the route screen-by-screen to make sure you didn't set up your route to cross hazards.

When using a CP your only option is vector, but on a PC screen raster will always show more detail for the same area. I use NOAA raster and vector with Coastal Explorer, and download the updated charts for my areas regularly in-season -- the program has a built-in utility that makes it very easy to click a button to do that.

[SailFastTri]

Originally Posted by SailFastTri

snip

When using a CP your only option is vector, but on a PC screen raster will always show more detail for the same area.

snip.

Meant "for the same area and chart scale".

[Surveyor]

Originally Posted by SailFastTri

All chart view software will remove detail at zoomed-out levels so hazards such as charted wrecks, rocks and reefs/shoals will not be displayed.

True. I created waypoints for every open ocean island and shallow bank in the world just for use with CM93 charts just for this very reason. If you zoom out far enough entire islands disappear and some entire countries too! The waypoints help to see where I am going (planning) when zoomed out.

I am working on doing the same thing for seamounts that rise to within 100 meters of the surface. I like to fish

[Zoef]

As vector maps are more frequently updated, at least in the Med, they should be your first choice. Raster maps are easier to read and give often a good impression of what the shore looks like. I use them both, whenever available.

[GPSNavX]

A couple useful links ..

Differences Between RNCs and ENCs

Differences Between Maps & Charts

[Wireless1]

Originally Posted by cal40john

So far I haven't made extensive use of electronic charts. What I have done is Garmin Bluecharts (vector) on my portable 76cx and NOAAs raster charts on Seaclear on a netbook.

I think you are spot on with some pretty good redundancy there. I also use raster charts at the nav station on a laptop running MapTech and at the helm I use a Garmin 546 with their Vision chip at the helm. The laptop is completely isolated from all the nav on the boat and is driven by a separate GPS (an el cheapo Garmin Etrex). Backing up the laptop are my real paper charts, chronometer, sextant, and HP41cx with some apps I wrote for it....enough redundancy for me. But, as I tell everyone... I am NOT going cruising!

[denverd0n]

Check the links provided by GPSNavX. Raster charts are NOT scanned images of paper charts. Not anymore they aren't. In fact, paper charts are printed images of the raster files.

I don't doubt that the raster files began life as scanned images of paper charts. That was some time ago, though. Nowadays it is the raster images that are maintained by cartographers using CAD software, and printed charts are simply produced from those raster images.