[Proj] Can I said the unit of Mercator Porjection? I'm trying to overlay shp file to google map.

[baijianhua]

I'm trying to overlay shape files(world map) to google map, I found that google 
map is using this PROJCS.

54004,PROJCS["World_Mercator",GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",SPHEROID
["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT
["Degree",0.017453292519943295]],PROJECTION["Mercator_1SP"],PARAMETER
["False_Easting",0],PARAMETER["False_Northing",0],PARAMETER
["Central_Meridian",0],PARAMETER["Standard_Parallel_1",0]

,UNIT["Meter",1]

,AUTHORITY["EPSG","54004"]]


I can get the same shape of google map(in world range, the top most level of 
google map), but one mismatch is the unit, the unit google map used is Decimal 
Degree, while Mercator Projection using is Meter, when I change this to 

54005,PROJCS["World_MercatorDD",GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",SPHEROID
["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT
["Degree",0.017453292519943295]],PROJECTION["Mercator_1SP"],PARAMETER
["False_Easting",0],PARAMETER["False_Northing",0],PARAMETER
["Central_Meridian",0],PARAMETER["Standard_Parallel_1",0]

,UNIT["Degree",0.0174532925199433]

,AUTHORITY["EPSG","54005"]]

Still I can not get the same coordinate value as google map, can anybody help? 
can I using the same unit with google map in Mercator projection result