>Date: Thu, 14 May 1998 19:38:27 -0400 >From: Rich Kulawiec <rsk_at_gsp.org> >Subject: Re: [Paddlewise] FW: Copying legally . . . > >On Thu, May 14, 1998 at 06:07:06PM +0000, R. Walker wrote: >> > Do you have any idea how big a file a scanned two-foot by three-foot >> > chart would require at 300 dpi? A quick calculation shows that to be >> > 77,760,000 pixels! >> >> Which is why USGS has their topos distributed on CDROM, not the >> web. Maybe a day will come when the internet can push a 77 meg >> file for individual use, but we are a ways away from that. > >As I've already pointed out, such files compress quite nicely -- and using >standard, publicly-available compression filters. There's no need >to push 77 Mbyte files around. The web *is* the appropriate means by >which to distribute these, especially since web technology can be >used to produce custom topos which include/exclude specific kinds of >features -- expanding and shrinking the size of the resulting data >files based on user preferences. > >Here, play with this as an example: > >http://pubweb.parc.xerox.com/map/color=1/db=usa/features=alltypes/ht=0.68/lat=4 >0.38/lon=-105.59/wd=1.36?227,169 > >It's Rocky Mountain National Park as seen by such a prototype-grade >implementation of just such an interface. > >- ---Rsk >Rich Kulawiec >rsk_at_gsp.org > >------------------------------ There is a big difference between a 300 Mb text file and a 300 Mb graphics file. With graphics the rule is the higher the compression the low quality of the resulting image(JPEG). file size for a 24 x 36 inch chart: 72 pixel per inch (ppi) RGB screen resolution = 12.8 Mb 120 ppi RGB low resolution to print on laser/ ink jet print at 60 Line per in. 35.6 Mb 200 ppi RGB resolution to print on laser/ ink jet print at 100 Line per in. =98.9 Mb 266 ppi CMYK file for lithographic reproduction 4 colour printing = 233.2 Mb Even if this images were jpeged the file size for a printable file would still take a hour plus to download. The map images found on the xerox site are very low resolution and would be impossible to navigate by. If I was navigating by these charts I would like them to be as high of quality as possible. also how many of us have printers capable of printing a 24 x 36 in. colour chart. The price to have this output at a commercial imaging centre would be more then the cost of the original chart. Bill Silver *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
On Fri, May 15, 1998 at 07:43:55AM -0500, Bill Silver wrote: > There is a big difference between a 300 Mb text file and a 300 Mb graphics > file. I'm well aware of that, having done imaging work for over 15 years, including writing the code for a commercial CT scanner and for a cardiac analysis tool. > With graphics the rule is the higher the compression the low quality of the > resulting image(JPEG). If it's lossy compression, yes. Lossless compression has no effect on picture quality. Most maps compress incredibly well with the latter; and accepting even a small amount of picture degradation (visible only to those who know what to look for) allows pretty amazing compression ratios. > Even if this images were jpeged the file size for a printable file would > still take a hour plus to download. I don't see this as a problem. I download files in the 5-20 Mbyte range all the time, and I'm running at 28.8 at home. The shift to 56 Kbit modems appears to be really happening, and other technologies (cable modems, ADSL, ISDN, etc.) are also vying to increase bandwidth. In 1-2 years, I suspect that connections at 128 Kbits will be ordinary with 1 Mbit connections available and affordable. > The map images found on the xerox site are very low resolution and would be > impossible to navigate by. As I said, it's of prototype quality. It's simply intended to demonstrate the idea, and provide a platform for development and experimentation. ---Rsk Rich Kulawiec rsk_at_gsp.org *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
At 07:43 AM 5/15/98 -0500, Bill Silver wrote: <snip> >If I was navigating by these charts I would like them to be as high of >quality as possible. >also how many of us have printers capable of printing a 24 x 36 in. colour >chart. >The price to have this output at a commercial imaging centre would be more >then the cost of the original chart. I print out 11 x 17 occasionally, sometimes 8-1/2 x 11 or 14, after tailoring them to my route and splicing them together--whether I got them electronically or from USGS/NOAA and copied them. I take as many sheets as necessary to cover the route. Because I'd just fold the 24 x 36's up and take two or three anyway, I don't see this as a problem. If it is, based on the way you operate, you could have a shop such as Kinko's (another ad? sorry. :-p ) print it on an oversize machine. You can print on coated paper up to 36" or even 48" wide and 250' (theoretically) long. You pay by the foot usually, plus a setup fee, but the cost is not too bad. A little more than buying a couple of NOAA charts, as of last November, but you could use the overlays we've talked about and get rid of the areas you aren't likely to end up. I'm just waiting on a totally waterproof, high processsor speed, high storage capacity, 13" screen PDA to use for my maps. I'd probably end up taking paper copies anyway, though.... Wynne Americus, GA USA *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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