From d0dbf48438f9e152314abf294467cb54f9ae0e70 Mon Sep 17 00:00:00 2001 From: Kristian Evers Date: Mon, 22 Jan 2018 21:06:23 +0100 Subject: Handle ellipsoid parameters correctly when using +nadgrids=@null. Fixes #22. Make sure to not change ellipsoid parameters to WGS84 when applying the null grid. Coordinates will still refer to the input ellipsoid so we keep the original parameters which in turn will be used when the coordinates are transformated to/from cartesian/geocentric space. Adjusted regression test material in nad/proj_outIGNF.dist slightly to accomodate numerical differences at the mm level. The transformations in question are at best accurate to about 1m so this shouldn't change real world usage of these transformations. --- src/pj_transform.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) (limited to 'src') diff --git a/src/pj_transform.c b/src/pj_transform.c index c72df2e7..6ad227cd 100644 --- a/src/pj_transform.c +++ b/src/pj_transform.c @@ -748,17 +748,30 @@ int pj_datum_transform( PJ *srcdefn, PJ *dstdefn, /* -------------------------------------------------------------------- */ if( srcdefn->datum_type == PJD_GRIDSHIFT ) { + const char* srcnadgrids = pj_param(srcdefn->ctx, srcdefn->params,"snadgrids").s; + pj_apply_gridshift_2( srcdefn, 0, point_count, point_offset, x, y, z ); CHECK_RETURN(srcdefn); - src_a = SRS_WGS84_SEMIMAJOR; - src_es = SRS_WGS84_ESQUARED; + /* If the gridlist has either "@null" or "null" as its only */ + /* grid we don't change the ellipsoid parameters, since the */ + /* datum shift to WGS84 was not performed in practice. */ + if ( strcmp("@null", srcnadgrids) && strcmp("null", srcnadgrids) ) { + src_a = SRS_WGS84_SEMIMAJOR; + src_es = SRS_WGS84_ESQUARED; + } } if( dstdefn->datum_type == PJD_GRIDSHIFT ) { - dst_a = SRS_WGS84_SEMIMAJOR; - dst_es = SRS_WGS84_ESQUARED; + const char* dstnadgrids = pj_param(dstdefn->ctx, dstdefn->params,"snadgrids").s; + /* If the gridlist has either "@null" or "null" as its only */ + /* grid we don't change the ellipsoid parameters, since the */ + /* datum shift to WGS84 will not be performed. */ + if ( strcmp("@null", dstnadgrids) && strcmp("null", dstnadgrids) ) { + dst_a = SRS_WGS84_SEMIMAJOR; + dst_es = SRS_WGS84_ESQUARED; + } } /* ==================================================================== */ -- cgit v1.2.3