[OSM-newbies] svg output

[Vangelis Katsikaros]

Richard Weait wrote:
> On Fri, Mar 12, 2010 at 1:02 PM, Vangelis Katsikaros <ibob17 at yahoo.gr> wrote:
> 
>> Hi again, well I had made a mistake. I though that the SVG output of OSM
>> kept the coordinates of the map points the same in the SVG (that the 0
>> of Greenwich, was also the x=0 in the SVG). But, I though wrong :)
> 
> Dear Vangelis,
> 
> No problem.  There are many ways to use OSM.  Finding the "right" way
> depends on what you want to do, and eventually depends on how you like
> to do things.  Let's look at your requirements in a little more
> detail.
> 
> You want to look at a substantial portion of the northern hemisphere.
> You want to show mostly plain coastlines
> You want to "overlay some GPS points"
> You want SVG output that you can manipulate in inkscape.
> 
> Tell us more about the GPS points.
> Are these points already objects in the OSM database?
> Could they be added to the OSM database?
> Are these points or collections of points in the form of tracks?
> Is there only one set of points and tracks or do they change at times?
> How often will you make a new map?

Hello Richard

Yes, these are indeed the requirements. The data I will overlay extend 
to the seas around Greenland, Scandinavia and some N Atlantic. I also 
want to see only coastlines and the land as a fill (like the Wikimedia 
Commons gray maps).

The points are not in the OSM database. The GPS points are tracks of 
ships (so I guess that they aren't of any interest to OSM). I converted 
them from AIS data, but converting to the proper format isn't a problem, 
since I can handle perl quite well (text based transformations are not 
an issue).

So, I have a list of points (right now it doesn't matter if they come 
from different objects) and the coordinates are from GPS data. I have 
converted that in the proper SVG <path>, so that when I put this <path> 
in the SVG with the map, it will be overlayed over the othe SVG elements.

Now, I don't know how often I will be making this map. But it will 
certainly won't be often (not more than once a month) (so there is no 
need for squeezing  out performance). Also once I have the map data 
(coastlines) I won't need to update them again.

> 
> And about the SVG.
> You mention post-processing in Inkscape. Was this to add your points?
> Perhaps that can be automated in an earlier step?  Probably more
> question about output once we complete the other requirements
> discussion.

I add the points in the SVG by scripting (just appending them in the 
right place). I though to use Inkscape, so that I can easily adjust 
things like colors, alpha channels or objects, or increase the stroke of 
paths. With many points, Inkscape can be rendered unusable. I can always 
import them in Gimp (and get a raster image), so as long as I format the 
SVG the way I want, there won't be a problem.

Thanks for your time guiding me through. I am not very experienced with 
handling and visualizing GIS data, so I am not familiar with the 
possible workflows and combination of tools to produce the outcome I 
want. Thanks again :)

Regards
Vangelis