What's the difference between using CRS defined as
+proj=longlat +datum=WGS84 +no_defs
and a CRS defined as
+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
Will using one or the other cause any problems. In the first case, how can GIS project properly without knowing which ellipsoid the data are referred to?
The datum=WGS84 includes the ellipsoid information hardcoded in PROJ:
http://svn.osgeo.org/metacrs/proj/trunk/proj/src/pj_datums.c
C_NAMESPACE_VAR struct PJ_DATUMS pj_datums[] = {
/* id definition ellipse comments */
/* -- ---------- ------- -------- */
"WGS84", "towgs84=0,0,0", "WGS84", "",
Apart from that, the WGS84 ellipsoid is default if no other is stated.
