where else to turn:
What are good books to get started on Cartography and GIS?
(For a complete newbie, that knows about math and computers)
Thank you
On 12/21/05, Rueben Schulz <[EMAIL PROTECTED]> wrote:
To Frankie,
Hi. You should be able to notice when the projection is changed. If uDig
does not know the CRS for your data (ie the *.prj file is missing on not
parsable) then it will not transform the data's coordinates. Attached is
a *.prj file that should work (assuming I got your shapefile name
correct). The prj file just has the WKT information on one line.
Your shapefile has latitude and longitude coordinates, which is a
geographic coordinate reference system. A geographic CRS (aka SRS) just
records datum information (among a few other things like axis order).
Your data is using the NAD83 datum. A projected CRS has a geographic CRS
+ a projection and projection parameters.
Also, if your map is shown on its side (90 degree rotation), try
changing the axis order in the *.prj file. The WKT says it is Lat/Long,
but shapefile coordinates are usually long/lat.
Since your data covers the entire world, some projections will cause
problems. For example, the poles cannot be projected with a mercator
projection (though if the extent info given below is correct, you might
be able to project everything with a mercator). Also, the transverse
mercator (used for UTM) is not well defined when you are greater than
about 30 degrees from a central meridian. I was hoping to address some
of these issues during the summer, but ran out of time. Also, not too
many people have needed to play with world maps.
Fortunately, uDig will only project data that is displayed on the map.
So if you want to try a UTM projection, zoom in to a valid area and then
change the projection. For example, zoom into the west coast of north
america and change the map's CRS to NAD83/UTM zone 10N.
I hope you can get this working. I couldn't get the new New Zealand Map
Grid projection working this morning, but I have not checked if it made
it into the new uDig release.
Oh, about your ps below. That is weird. According to the WKT the data is
not projected.
Rueben
On Tue, 2005-20-12 at 10:11 +0100, Frankie Bollaert wrote:
> Hello Rueben,
>
> First of all thank you, I had installed uDig some time ago, but I had
> not noticed this button at the bottom.
>
> Using vmap0 data that I had acquired from mapMart I think I was able
> to change the projection that uDig used. (I am not totally sure
> because the map is too small.)
>
> But using the shapefiles I made myself from the vmap0 data from NIMA I
> was not able to change the projection. Even after I made a .prj file
> using notepad, using the following data that I got from ogrinfo:
>
> Using ogrinfo I got this from the original data:
> $ /cygdrive/c/gis/FWTools/bin/ogrinfo.exe
> gltp:/vrf/gis/vmap0/v0eur/vmaplv0/rference '[EMAIL PROTECTED]
> (*)_area' | less
> ERROR 4: OGDI Driver doesn't support update.
> Had to open data source read-only.
> INFO: Open of `gltp:/vrf/gis/vmap0/v0eur/vmaplv0/rference'
> using driver `OGDI' successful.
>
> Layer name: [EMAIL PROTECTED](*)_area
> Geometry: Polygon
> Feature Count: 2136
> Extent: (- 179.999900, -89.999900) - (179.999900, 83.623596)
> Layer SRS WKT:
> GEOGCS["NAD83",
> DATUM["North_American_Datum_1983",
> SPHEROID["GRS 1980",6378137,298.257222101,
> AUTHORITY["EPSG","7019"]],
> TOWGS84[0,0,0,0,0,0,0],
> AUTHORITY["EPSG","6269"]],
> PRIMEM["Greenwich",0,
> AUTHORITY["EPSG","8901"]],
> UNIT["degree", 0.0174532925199433,
> AUTHORITY["EPSG","9108"]],
> AXIS["Lat",NORTH],
> AXIS["Long",EAST],
> AUTHORITY["EPSG","4269"]]
>
> I have no clue why this is, aren't the coordinates used in the
> shapefile simple longitudes and latitudes? That should mean you
> should be able to display them in no matter what projection?
>
> Have a nice day,
> Frankie
>
>
> ps. When I use the vmap0 data from the geotools program, it says it
> is using a Cartesian projection.
--
Frankie
