deformation: Replace +t_obs with +dt

The +t_obs parameter was confusing for users since it effectively
overwrote the observation time in input coordinates. To make it more clear
what is the operation is doing, users are now required to directly specify
the time span for which they wish to apply a given deformation. The parameter
+dt has been added for that purpose. The new parameter is mutually
exclusive with +t_epoch. +dt is used when deformation
for a set amount of time is needed and +t_epoch is used (in
conjunction with the observation time of the input coordinate) when
deformation from a specific epoch to the observation time is needed.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/proj_internal.h b/src/proj_internal.h
index 9ffcc2b3..b7e3de9e 100644
--- a/src/proj_internal.h
+++ b/src/proj_internal.h
@@ -677,6 +677,7 @@ struct FACTORS {
 #define PJD_ERR_TOO_MANY_INITS          -57
 #define PJD_ERR_INVALID_ARG             -58
 #define PJD_ERR_INCONSISTENT_UNIT       -59
+#define PJD_ERR_MUTUALLY_EXCLUSIVE_ARGS -60
 /* NOTE: Remember to update src/strerrno.cpp, src/apps/gie.cpp and transient_error in */
 /* src/transform.cpp when adding new value */