>> If NOAA charts are public domain . . . why doesnt someone do us all a big favor and scan them and post them on the net? Might put a few NOAA dealers out of business, I suppose, but why should we all pay for what we have already bought (as taxpayers) anyway? In fact, why doesnt NOAA just post its charts digitally? Could it be that the people who make money reproducing them and selling them would howl too loudly? >> ************************************************************************** * 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! Chuck Holst *************************************************************************** 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 Thu, May 14, 1998 at 12:41:46PM -0500, Chuck Holst 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! So it's 77M at 8 bits/pixel: no problem. Do have any idea how compressed that file would get if you rendered it as a JPG (or via any other decent compression scheme)? There is an enormous amount of spatial redundancy in most images. (I've worked at a couple of different jobs in the medical imaging field, one of which involved routinely generating 300 MByte data files in a few seconds. They wound up around 8-14 Mbytes after compression.) ---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 03:00 PM 5/14/98 -0400, Rich Kulawiec wrote: >On Thu, May 14, 1998 at 12:41:46PM -0500, Chuck Holst 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! > >So it's 77M at 8 bits/pixel: no problem. > >Do have any idea how compressed that file would get if you rendered >it as a JPG (or via any other decent compression scheme)? There is >an enormous amount of spatial redundancy in most images. > >(I've worked at a couple of different jobs in the medical imaging field, >one of which involved routinely generating 300 MByte data files in a >few seconds. They wound up around 8-14 Mbytes after compression.) Gee, I'm beating this to death.. Compressed Tiffs give the highest final resolution and are lots smaller. They may get the best ratio..any real graphics nerds out there? Wynne Americus, GA *************************************************************************** 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 Thu, May 14, 1998 at 11:53:54PM -0400, Wynne Eden wrote: > Compressed Tiffs give the highest final resolution and are lots smaller. > They may get the best ratio..any real graphics nerds out there? Yes, here. (Raises hand) Actually, JPG will do much better than tiff *unless* you use a tiff format that excludes a lot of the overhead (such as multiple-resolution views of the same image). But by the time you've done that...you might as well have used JPG, which (a) is supported by many browsers (b) is under active development by a standards group and (c) is computationally less intensive to deal with than tiff. BTW, there are some other map sites there that y'all might want to visit; here are the URLs: <li> <a href="http://www.mapquest.com/"> Welcome To MapQuest!</a> <li> <a href="http://www.city.net/maps/"> Excite Maps: Browse All Maps</a> <li> <a href="http://www.infospace.com/"> The Ultimate Directory - InfoSpace</a> <li> <a href="http://www.pathfinder.com/travel/maps/"> Pathfinder Maps</a> <li> <a href="http://www.mapmania.com/"> Online Mapping - Chicago Map Corp</a> <li> <a href="http://www.mapsonus.com/"> Maps On Us: A Map, Route and Yellow Pages Service</a> <li> <a href="http://tiger.census.gov/cgi-bin/mapsurfer"> Tiger Map Server Browser</a> <li> <a href="http://route30.delorme.com/"> DeLorme: CyberRouter</a> <li> <a href="http://maps.yahoo.com/yahoo/"> Yahoo! Maps</a> <li> <a href="http://www.theodora.com/maps/abc_world_maps.html"> Quick Maps of the World - Flags, Maps, Economy, Geography, Climate, Natural Resources, Current Issues, International Agreements, Population, Social Statistics, Political System</a> <li> <a href="http://www.geo.ed.ac.uk/home/ded.html"> Bruce Gittings' Digital Elevation Data Catalogue </a> <li> <a href="http://edcwww.cr.usgs.gov/glis/hyper/guide/1_dgr_dem"> 1-Degree USGS Digital Elevation Models</a> <li> <a href="http://www.zilker.net/~hal/apl-us//"> JHU/APL Digital Relief Map of the US (Composites Browser)</a> <a href="http://pubweb.parc.xerox.com/map/db=usa"> Xerox PARC Map Viewer, USA database</a> <a href="http://pubweb.parc.xerox.com/map/"> Xerox PARC Map Viewer, World database</a> The Tiger map browser is a fun one to interact with; it lets you turn various features off and on and redraws the map accordingly. ---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/ ***************************************************************************
> 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. Besides at $3 or so a copy, CDROM is the correct distribution and storage method for such files. *************************************************************************** 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 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=40.38/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 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Assuming I sent my earlier post to the list... The USGS quads South Carolina DNR has on its site range in size from 7-24 megs. I couldn't d/l them until I had a T1 line because my server kept timing out on most of them. They are still worth having. I'd be willing to pay for zip disks or cds of NOAA charts. Hint, hint, for you entrepreneurs out there. At 12:41 PM 5/14/98 -0500, Chuck Holst wrote: > >>> >If NOAA charts are public domain . . . why doesnt someone do us all a >big favor and scan them and post them on the net? Might put a few >NOAA dealers out of business, I suppose, but why should we all pay >for what we have already bought (as taxpayers) anyway? > > In fact, why doesnt NOAA just post its charts digitally? Could it >be that the people who make money reproducing them and selling them >would howl too loudly? >>> > >************************************************************************** * > >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! > >Chuck Holst >*************************************************************************** >PaddleWise Paddling Mailing List >Submissions: paddlewise_at_lists.intelenet.net >Subscriptions: paddlewise-request_at_lists.intelenet.net >Website: http://www.gasp-seakayak.net/paddlewise/ >*************************************************************************** > > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Rich provided a link to the Zerox PARC map viewer.This may be a bit off topic, but while digital charts are not really accessible to most paddlers today, they will be much more widely used in the future. GIS has been around for a while, and the technology to provide interactive access to digital maps over the web is pretty much in its infancy, but developing really fast. This discussion started asking questions about storage space for scans of paper maps, but the future lies with geographic information systems that store the individual features on the map digitally. A scan of a paper map yields only a degraded raster image of the original map at the scale it was originally drawn, and on the projection it was originally drawn - the real power comes when the features on the map are stored as a collection of vectors. In the vector model features that you see on a map are represented by a series of lines, points or polygons stored as a string of coordinates. If you imagine that you have say a paper chart showing an island coastline, most of the map is redundant white space, but you still have to store the whole chart when it is scanned. This is obviously a simple case, and compression software would also do a good job here, but in the vector model you only store the features you want (if our hypothetical island was square, this would require a polygon consisting of four pairs of co-ordinates, and a label identifying the polygon as the island). In general if your maps represent contiunously changing surfaces then raster scans offer good storage/access efficiency, but if you are interested in a collection of discrete features (such as islands, depth soundings, coastlines, roads) then vector systems win in effeciency and have the major benefits that you can select the features that you want to display, scale, project, and symbolise the map as you wish, and perform spatial analysis (accurately measuring area, distance, proximity, plot waypoints, create 3D terrain models etc etc etc). I'll stop rambling about this on this list ... but if anyone is interested in digital mapping, they could do worse than download the free web client/lightweight GIS from ESRI at: http://www.esri.com/base/products/arcexplorer/arcexplorer.html and have a play with some of ESRI's online map data. HTH Cheers Colin *************************************************************************** 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 10:34 AM 5/15/98 +0100, Colin Calder wrote: > >I'll stop rambling about this on this list ... but if anyone is interested >in digital mapping, they could do worse than download the free web >client/lightweight GIS from ESRI at: > >http://www.esri.com/base/products/arcexplorer/arcexplorer.html > >and have a play with some of ESRI's online map data. > I think the rambling appropriate, but I'm a list newbie... Have you used any of the digital overlay data some gov't organizations (at least in the US0 are providing for map overlays? I haven't taken the time to figure out how to use it, but it looks promising for backcountry ramblers or small river runners. It can give very accurate boundaries of private/public land, more up-to-date locations of facilities (restroom or hospital), etc. 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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