I've already done the repairing of the line connection across the Int'l Date Line, so that is not a problem. I'm not sure that I see here a suggestion about what is my main problem - that of having a "view" of -180 - 180, even though the coordinates of the map points have been converted to 0-360 (i.e, half of the rectangular frame of the map is blank, since out of range map points are not plotted). Is Transform instead of Mark/Compute/Unmark the key, or do I have to modify the macro (or the WDBI data points) ? I've never used Transform - what is the difference in its effect vs. Mark/Compute/Unmark of positions ?
On Feb 12, 10:48pm, Lloyd A Treinish wrote: > Subject: Re: [opendx-users] World Map coordinate system > > The file, WDBI.dx, used by that macro has the coordinates as provided in > the original World Data Bank I file. The coordinates are raw lat-lon, > cylindrical equidistant, with lon as degrees east (-180 to 180). A simple > transformation such as Mark/Compute/Unmark or Transform will only partially > work. The problem is lines that cross a nominal Int'l Date Line. That > transformation will force the "pen" to scrawl across the page. You would > have to check for these particular lines after the transformation and > repair them. > > If you want to see ASCII, you can Import and then Export in an ASCII flavor > .dx file. > > The package of projections I put together some many years ago is geared > around data in [lat degrees north, lon degrees east, +/- 180]. This was > fine for my own needs at that time. Since there was not much user interest > then, there wasn't much motivation to make them more general-purpose. You > would have to modify the map file or use a different one and/or modify your > data. Some of the projections may have to be changed because of the > different coordinates. At least with everything as macros, you can see how > the projections work and modify them. > > > > "Sharon Cady" <[EMAIL PROTECTED]>@opendx.watson.ibm.com on > 02/12/2001 02:58:07 PM > > Please respond to [email protected] > > Sent by: [EMAIL PROTECTED] > > > To: [email protected] > cc: > Subject: [opendx-users] World Map coordinate system > > > > I'm almost embarrassed to ask, since I'm obviously missing something > (probably > simple), but how do I shift the coordinate system of the cylindrical > equidistant (rectangular) global map so that it goes not from -180 to -180 > degrees longitude but instead ranges 0-360 ? > > There are inputs into WorldMapProjections which ask for centroid of the > projections and also the range, but manipulation of these don't change the > positions of the points in the map, just the view of what is plotted (it > seems). I've tried shifting the positions myself (mark/compute); however, > with > my new map ranging 0-360 longitude, I can only see the 0-180 part (the > 180-360 > is ignored, apparently). Is there something somewhere which limits the view > of > this plotted object ? I looked in the wdbi.dx file to see if I could find > anything, but I didn't really see much in there, except binary data. > > I can get a map to plot which "looks" like how I want it, but of course the > positions are incorrect, since they are forced to range -180 - 180. My data > won't overplot on this, unless I juggle that all around too. > > > >-- End of excerpt from Lloyd A Treinish
