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Old 27-03-2012, 08:41   #16
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Re: Raster Charts or Vector Charts - Which is Best for Electronic Navigation ?

Not quite sure what you're saying. Raster charts came from scanned paper charts. They are updated digitally. So you're saying that because they've been updated they no longer are considered to have come from scanned material?

I've never read anything about a raster chart created digitally from the beginning. Are new raster charts being made? On a computer from scratch?

From link above:
In 1994, OCS began to scan all of the negatives used for chart printing. From this library of digital files, cartographers are able to update charts efficiently utilizing Computer Aided Design (CAD), a software commonly used for drafting. From these files, paper charts continue to be printed.


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Originally Posted by denverd0n View Post
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.
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Old 27-03-2012, 16:39   #17
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Re: Raster Charts or Vector Charts - Which is Best for Electronic Navigation ?

Actually, if you are interested here is NOAA's explanation of how they make charts. Cartographic Automation
Also at the bottom of the page they discuss Vector charts - ENC / S-57

Currently they use CADCAM to process and "update" the chart files. The retail "Charts on Demand" at the retailer's store (if he is equipped) has a machine that accesses the current chart file at NOAA and prints out the chart for you. That's about as "up to date" as you can get from NOAA.

Or you can access these chart files yourself and download them as raster files.
RNC Downloads
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Old 28-03-2012, 07:48   #18
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Re: Raster Charts or Vector Charts - Which is Best for Electronic Navigation ?

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Originally Posted by cal40john View Post
So you're saying that because they've been updated they no longer are considered to have come from scanned material?
No, I never said that. In fact, I specifically said that the raster files began life (decades ago) as scans of printed charts, so of course they originally came from scanned material.

I was simply trying to clarify, for anyone who did not realize it, that NOAA has long since finished scanning in all of the paper charts. They don't do that anymore. Scanned the last paper charts more than a decade ago. They now maintain the raster files as the "master" and generate paper charts by simply printing out the raster images.
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Old 28-03-2012, 08:04   #19
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Re: Raster Charts or Vector Charts - Which is Best for Electronic Navigation ?

I like both. We started with vectors but soon we found that for some areas vectors were poor or non-existent and then we 'discovered' rasters.

To me both types are good stuff.

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Old 28-03-2012, 20:56   #20
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Re: Raster Charts or Vector Charts - Which is Best for Electronic Navigation ?

Ah, found it. for those with too much time and too much curiosity about nautical charting - the NOAA charts were transferred from "acetates/negatives" to the digital form. The paper charts were produced by layers of negatives (one for each color or type of information) put together and then printed on the paper. The paper is not the original but the product of the "acetates/negatives."

It is all explained here: Differences Between RNCs and ENCs
along with some good information about ENC's and ECDIS.
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