Lars Aronsson wrote:
I want to plot a nice OpenStreetMap of Europe and any ugly
"longlat" or Mercator is out of the question. I've read "Web
Mapping Illustated" and successfully installed the "proj" program.
In that book, the turning point is when the map of Canada is
turned into the LCC projection (EPSG:42304) on pp. 188-189.
In my mind, a nice map of Europe looks like this one that I
scanned from an out-of-copyright 1925 encyclopedia,
http://commons.wikimedia.org/wiki/Image:Pieni_1_0471.jpg
What projection is that? What arguments should I give to "proj"
to reproduce this projection?
As you can see, lon_0=20 in this case, in order to cover all of
Europe from Portugal to the Ural. Also, all of the Mediterranean
is covered, down to the Gulf of Sirte (32 N, 18 E) and even a
corner of the Persian Gulf. The map center is near Warsaw (52 N).
I reckon lat_1 and lat_2 are the latitudes where the projection
cone intersects the Earth and that lat_2 defaults to the value of
lat_1, making it a tangent case. But how should I pick lat_1 and
lat_2 given the coverage area of my map? Should I simply split
the latitudes in thirds, so that my span from 30 N to 75 N (along
the center longitude) gives lat_1=45 and lat_2=60 (i.e. Belgrade
and Stockholm)?
My source data from OpenStreetMap.org is in WGS84.
How is AEA (Albers Equal Area) different from LCC?
The answers to these questions were not obvious to me from reading
the proj man page. My best guess is:
proj=lcc ellps=WGS84 lon_0=20 lat_0=0 lat_1=45 lat_2=60
Lars,
This would be a good question to ask on the proj mailing list. The
Canadian LCC projection renders as the following for PROJ.4:
+proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0
+ellps=GRS80 +datum=NAD83 +units=m +no_defs
I'm not really clear on all the implications for LCC, but I would
be tempted to have Standard Parallel 1 (ie. +lat_1) somewhere
about 1/3 of the way from the bottom of the map, and Standard Parallel
2 somewhere around 1/3 from the top of the map. I would expect the
latitude of origin to be in the middle, though I see that for
42304 it was the same as the bottom parallel.
So, I'd suggest trying something like:
+proj=lcc +lon_0=20 +lat_0=52 +lat_1=40 +lat_2=64 +datum=WGS84
I'm sure savvier people than I could give a better answer.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | President OSGF, http://osgeo.org
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