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How does a proj-string (UTM) w/o a zone number work?

Question asked by yaw19018_connecticut on Apr 25, 2020
Latest reply on Apr 25, 2020 by Dan_Patterson

Software: RStudio

Data: a world elevation map, elev, which was downloaded from Manuel Gimond's web site

The original crs is as follows:

+proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +no_defs


I did a test as follows, just out of curiosity:

elev_projected <- projectRaster(elev, crs = "+proj=utm +ellpse=WGS84")  # the +zone= parameter not specified 


In ArcGIS Desktop, when projecting to UTM, we have to specify which specific zone to use. R, however, seems to allow this to happen w/o complaining. Even though there was a warning message, the raster was projected anyway. 

3 projected point(s) not finite


The extent of the output is as follows:

xmin       : -14587336  xmax       : 14350664  ymin       : -19985214  ymax       : 20161986


I wonder what actually happens when the zone parameter is missing from the proj string. Does this string make any sense? The output map is attached. Thanks.