[Proj] What is the difference between proj and cs2cs command?

[kochizufan]

Hello,

I've believed for a long time that,

proj +proj=some_definition

and 

cs2cs +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +to
+proj=some_definition

is same meaning.


But I tried this:

proj -f %.6f +proj=tmerc +lat_0=0 +lon_0=-62 +k=0.9995000000000001
+x_0=400000 +y_0=0 +ellps=clrk80 +towgs84=725,685,536,0,0,0,0 +units=m
+no_defs
-61.35 15.42 0
469737.400664	1704564.737169 0

cs2cs -f %.6f +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +to
+proj=tmerc +lat_0=0 +lon_0=-62 +k=0.9995000000000001 +x_0=400000 +y_0=0
+ellps=clrk80 +towgs84=725,685,536,0,0,0,0 +units=m +no_defs
-61.35 15.42 0
468774.391590	1704156.539473 14.452425

These cases return different results.


And, I used pj_transform C function directly, from WGS84 to target
projection, it returns same result
with proj. 
(469737.400664  1704564.737169)



What is the difference between proj and cs2cs? 
My task is making test case of pj_transform function, which result I should
believe?

Thanks,
Ko-hei



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