Opened 13 years ago
Closed 13 years ago
#3737 closed defect (fixed)
NAD27 expands to use towgs84 instead of grid shift files
| Reported by: | warmerdam | Owned by: | warmerdam |
|---|---|---|---|
| Priority: | normal | Milestone: | |
| Component: | OGR_SRS | Version: | unspecified |
| Severity: | normal | Keywords: | nad27 |
| Cc: | Even Rouault |
Description (last modified by )
For reasons that are not clear, the expansion of "NAD27" in OGRSpatialReference::SetWellKnownGeogCS() has include a TOWGS84[] approximation in the WKT for a very long time.
With the introduction of r19903 the translation of the WKT to PROJ.4 format uses a +towgs84 parameter instead of the +nadgrids directive (previously implicit from +datum).
On a related note the current expansion of EPSG:4267 (NAD27) uses a towgs84 value from the datum_shift.csv.
Change History (2)
comment:1 by , 13 years ago
| Description: | modified (diff) |
|---|
comment:2 by , 13 years ago
| Resolution: | → fixed |
|---|---|
| Status: | new → closed |
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Several related changes made. First libgeotiff's build_pcs.py was adjusted to avoid putting a towgs84 parameter in for NAD27 (http://trac.osgeo.org/geotiff/changeset/1889).
Changes to ensure +datum=NAD27 is used if there is no TOWGS84 parameter applied in trunk (r20501) along with changes to avoid putting out +ellpse if +datum is present and removing TOWGS84 from the well known expansion of NAD27. A few test suite changes made related to this also in trunk (r20500).