Thanks Graham and Alex.
I've looked at your links, then searched for Spherical Mercator Projection
and have found some details here:
http://wiki.openstreetmap.org/wiki/Mercator
http://wiki.openstreetmap.org/wiki/Mercator
At the end of the page there is an online converter: the coordinates i've
found in the example doesn't mach the converted real Lat/Lon.
As far as i've understood since now, there are numbers of reference systems,
each one with one datum point from which start counting with a specified
unit. (Please tell me if i'm wrong!)
So basically, to make the map of a certain area i've to call the zoom_to_box
function,
specifing the bottom left and upper right corner of the box, using
datasource coordinates format.
Now i've downloaded Italy.osm.bz2 and loaded into PostGres via osm2pgpsql.
I've changed the datasource code for every layer with the following:
parameters p;
p["type"]="postgis";
p["host"]="127.0.0.1";
p["port"]=5432;
p["dbname"]="gis";
p["user"]="postgres";
p["table"]="planet_osm_roads"; //This is the only table which
doesn't cause error
p["password"]="";
I've tried several coordinates but now i'm still unable to get a non blank
map.
Which type of coordinates have i to use now? how to discover it?
I've also looked at the Proj4 software and, always stading to what i've
understood,
it's a cli converter which accept args like:
+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m
+no_defs
and convert from lat lon in the desired system.
But again, not knowing the correct string to use with OSM is making me
unable to obtain the box coordinates.
Please help me getting out these tunnel!
I promise i'll make a tutorial after having understood the entire scenario.
Thanks for your support guys!
Gianluca Sorrentino
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