<div>Hello I sending this output from cs2cs ( proj library convertion tool ) to see if that can be a bug or misconcept.<br></div><div>I tried to transform geographic coordinates from on Earth figure to another figure, basic datum change.</div>
<div><br></div><div>cs2cs -E -v +init=epsg:4618 -f "%.12f" +to +proj=longlat +ellps=WGS84 +towgs84=0,0,0<br># ---- From Coordinate System ----<br>#Lat/long (Geodetic alias)<br>#<br># +init=epsg:4618 +proj=longlat +ellps=aust_SA +no_defs<br>
# ---- To Coordinate System ----<br>#Lat/long (Geodetic alias)<br>#<br># +proj=longlat +ellps=WGS84 +towgs84=0,0,0<br>-7 -1<br>-7 -1 -7.000000000000 -1.000000000000 0.000000000000</div><div><br></div><div>By the output above is clear that it does not make the transformation.</div>
<div>I could discover the reason. It is the missing +towgs84 from source srid. I attached it in command line below and got different results.</div><div><br></div><div>cs2cs -E -v +init=epsg:4618 +towgs84=-67,3,-38,0,0,0,0 -f "%.12f" +to +proj=longlat +ellps=WGS84 +towgs84=0,0,0<br>
# ---- From Coordinate System ----<br>#Lat/long (Geodetic alias)<br>#<br># +init=epsg:4618 +towgs84=-67,3,-38,0,0,0,0 +proj=longlat +ellps=aust_SA<br># +no_defs<br># ---- To Coordinate System ----<br>#Lat/long (Geodetic alias)<br>
#<br># +proj=longlat +ellps=WGS84 +towgs84=0,0,0<br>-7 -1<br>-7 -1 -7.000046608443 -1.000353975944 -43.192882359959</div><div><br></div><div>So looks like the cs2cs tool requires +towgs84 on both source and destination to compute coordinate change.</div>
<div>I expected that proj utils complained about this missing parameter.</div><div>Also trying a st_transform on postgis package behaves like the cs2cs command line. It does not transform the geometry.</div><div>I expected that function reported something if it can not make the transformation.</div>