FME version: 2016.1.3.2 (20170214 - Build 16717 - WIN64)
Hi, i am trying to create a custom coordinate system (custom ellipsoid, custom datum, custom transformation and custom crs).
The CRS i am trying to create is the EPSG:26331 (as parametrized by EPSG).
Looking at the Coordinate System Gallery, there is a crs with name equal to EPSG:26331 (i will call this FME EPSG:26331)..
But there is two points that i want to modify:
- Ellipsoid Parameters
- Datum Parameters.
- Ellipsoid Parameters:
Searching into EPSG Registry (http://epsg-registry.org), the ellipsoid used by EPSG:26331 is EPSG:7012 - Clarke 1880 (RGS). This ellipsoid has:
- semi-major axis (E_RAD): 6378249.145 meter
- inverse flattening (inv_f): 293.465.
using P_RAD = E_RAD 81-(1/inv_f)] = 6356514.8695497755
In FME, this same ellipsoid has:
- semi-major axis (E_RAD): 6378249.1449999996 meter
- semi-minor axis (P_RAD): 6356514.8700000001.
using the same formula above, we get inv_f = 293.4650060791153. A little different from what is in EPSG. (this was one of the motivation to customize this CRS).
2. Datum Parameters
DELTA_X: -92
DELTA_Y: -93
DELTA_Z: 122
DESC_NM: Minna, Nigeria
ELLIPSOID: CLRK80
SOURCE: US Defense Mapping Agency, TR-8350.2-B, December 1987
USE: MULREG
I want to use GEOCENTRIC method (this is the second motivation to customize this CRS).
So i create the custom ellipsoid, the custom datum, custom datum transformation and the crs (they are below).
ELLIPSOID_DEF CLARK_1880_RGS \
DESC_NM "EPSG:7012 - Clarke 1880 RGS - a=6378249.145 e inv_f=293.465" \
SOURCE "EPSG V9.2" \
E_RAD 6378249.145 \
P_RAD 6356514.8695497755
#-----------------------------
# MINNA - Nigeria EPSG:4623
#-----------------------------
DATUM_DEF MINNA_NIGERIA \
DESC_NM "EPSG:6263." \
SOURCE "EPSG V9.2" \
ELLIPSOID CLARK_1880_RGS
#ELLIPSOID CLRK80
# Minna-Nigeria (EPSG:6263) para WGS-1984 (EPSG:4326) - EPSG:1168
# -------------------------------------
# SRC_DTM "MINNA" \
XFORM_DEF Minna_to_WGS_1984_2 \
SRC_DTM "MINNA_NIGERIA" \
TRG_DTM "WGS84" \
DESC_NM "Minna-NIG to WGS1984. DMA-Nga" \
SOURCE "EPSG v9.2" \
GROUP "custom" \
EPSG_NBR 1168 \
INVERSE "Yes" \
METHOD "GEOCENTRIC" \
DELTA_X -92.0 \
DELTA_Y -93.0 \
DELTA_Z 122.0
# UTM MC 3E / 31N MINNA_NIGERIA - EPSG:26331
# DT_NAME MINNA \
COORDINATE_SYSTEM_DEF "UTM-31N.Minna-NIG" \
DESC_NM "UTM MC3E/31N Minna - NIG." \
DT_NAME MINNA_NIGERIA \
GROUP "custom UTM" \
SOURCE "custom" \
PROJ UTM \
PARM1 31 \
PARM2 1 \
MAP_SCL 1 \
UNIT METER
COORDINATE_SYSTEM_DEF "TM-6E.WGS1984"\
DESC_NM "Transversa de Mercator, MC6E, FE 500k, FN 0, WGS-1984"\
DT_NAME WGS84 \
GROUP "custom TM" \
SOURCE "custom" \
PROJ TM \
PARM1 6 \
ORG_LAT 0 \
SCL_RED 0.9996 \
X_OFF 500000 \
Y_OFF 0 \
UNIT METER
Using the workflow (attached: ), i test the transformation from EPSG:26331 to TM-6E.WGS1984 (custom crs).
I get this response from log and no transformation is done.
CS-MAP Reprojector: User specifed transformation 'Minna_to_WGS_1984_2' will be used for 'UTM-31N.Minna-NIG' -> 'TM-6E.WGS1984'
Reprojector: Using transformation `Minna_to_WGS_1984_2,Forward(Geocentric,EPSG:1168)' when reprojecting from UTM-31N.Minna-NIG to TM-6E.WGS1984
Geocentric inverse calculation failed to converge.I tried changing the custom datum transformation, setting "Inverse" to no (i only want to transform from Minna to WGS-84, the reverse transformation is not needed right now).
I change the custom datum transformation in file MyCoordSysDefs.fme, close the FME Workbench, reopen but any change to this parameter is ignored (inspect the datum transformation show the "Inverse" always as yes even when i change that to no).
If i choose to use the build-in ellipsoid (CLRKE80) instead the custom ellipsoid (CLARK_1880_RGS), everything works.
Am i doing something wrong with the custom ellipsoid or with the edition of MyCoordSysDef.fme file?