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<TITLE>Newbie... Locations, Projections, Regions, choices? (long)</TITLE>
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<FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>All,<BR>
<BR>
I need to create 6 regional maps of the continental U.S., north and south by west, central, and east. My first thought was to create 7 locations (one for the entire continental US) but my second thought was to create just one location with the default region as the entire continental US and 6 other regions. Is this sound logic?<BR>
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First I downloaded the States data from the National Atlas. I then created a latitude - longitude location and imported the shape file excluding Alaska, Hawaii, Puerto Rico, and the Virgin Islands.<BR>
> g.proj -p<BR>
-PROJ_INFO-------------------------------------------------<BR>
name : Latitude-Longitude<BR>
datum : wgs84<BR>
towgs84 : 0.000,0.000,0.000<BR>
proj : ll<BR>
ellps : wgs84<BR>
-PROJ_UNITS------------------------------------------------<BR>
unit : degree<BR>
units : degrees<BR>
meters : 1.0<BR>
<BR>
> g.region -p<BR>
projection: 3 (Latitude-Longitude)<BR>
zone: 0<BR>
datum: wgs84<BR>
ellipsoid: wgs84<BR>
north: 49N<BR>
south: 25N<BR>
west: 125W<BR>
east: 67W<BR>
nsres: 0:00:30<BR>
ewres: 0:00:30<BR>
rows: 2880<BR>
cols: 6960<BR>
cells: 20044800<BR>
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The map displays fine but I want to change the projection to Albers Equal Area or Lambert Conformal Conical since it is such a large area. So I created a new location: aeaConUS with one caveat. It said the eastern value had to be larger than the western value so I (perhaps wrongly) used –125 for the western boundary and –67 for the eastern. Using the GUI selected the “Vector>Develop map>Reproject vector” menu item and selected the vector from the above location. Here is what the new location and default region looks like:<BR>
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> g.proj -p<BR>
-PROJ_INFO-------------------------------------------------<BR>
name : Albers Equal Area<BR>
datum : wgs84<BR>
towgs84 : 0.000,0.000,0.000<BR>
proj : aea<BR>
ellps : wgs84<BR>
a : 6378137.0000000000<BR>
es : 0.0066943800<BR>
f : 298.2572235630<BR>
lat_0 : 23.0000000000<BR>
lat_1 : 29.5000000000<BR>
lat_2 : 45.5000000000<BR>
lon_0 : -96.0000000000<BR>
x_0 : 0.0000000000<BR>
y_0 : 0.0000000000<BR>
-PROJ_UNITS------------------------------------------------<BR>
unit : mile<BR>
units : miles<BR>
meters : 1609.3440000000<BR>
<BR>
> g.region -p<BR>
projection: 99 (Albers Equal Area)<BR>
zone: 0<BR>
datum: wgs84<BR>
ellipsoid: wgs84<BR>
north: 49<BR>
south: 25<BR>
west: -125<BR>
east: -67<BR>
nsres: 0.05<BR>
ewres: 0.05<BR>
rows: 480<BR>
cols: 1160<BR>
cells: 556800<BR>
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When I first try to display this map, nothing is displayed unless I select “Zoom display to selected map” at which point my nice Albers map gets displayed. Or I can “zoom out” about 20 times to make the Albers map start showing up near the top of the screen. Obviously I’m doing something wrong here but I’m not sure if its the units (meters vs miles) or something more fundamental.<BR>
<BR>
<BR>
Drowning in a sea of GRASS and loving it!<BR>
<BR>
Thanks for any<BR>
suggestions,<BR>
<BR>
Randy</SPAN></FONT>
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