tissot() gains a method argument
(default "proj"). The new "proj" method
delegates to PROJ::proj_factors(), calling the PROJ C
library directly for exact distortion factors rather than approximating
them via finite differences. This is more accurate, especially for
tabular or piecewise projections (e.g. Robinson). The original
finite-difference computation (Snyder 1987), inspired by Bill Huber’s
formulation at https://gis.stackexchange.com/a/5075/482, is preserved
as method = "finitediff". The PROJ package is
now the sole coordinate transformation dependency;
gdalraster has been removed.
tissot_raster() computes distortion surfaces on a
regular projected grid, returning a tissot_raster object
with image() and plot() methods. Extent is
auto-detected from the global lon/lat bounding box (clamped by
radius) or supplied explicitly. Supports any metric from
[tissot()] output.
gdalraster removed from Imports. All
coordinate transformation now goes through
PROJ::proj_trans() and PROJ::proj_crs_text().
CRS validation (srs_is_geographic) is handled by an
internal helper using PROJ::proj_crs_text().metrics in tissot_raster():
names now use underscores ("scale_area",
"scale_h", "scale_k") matching the actual
tissot_tbl column names (previously used dots, causing
silently all-NA output).Major refactor — modernized engine, new API, and rich plotting.
Projection engine switched from reproj to
transform_xy() from gdalraster. All projection work is now
a single batched GDAL call.
API renamed: proj.in/proj.out →
source/target, following reproj conventions.
target is the second positional argument (required);
source defaults to "EPSG:4326".
tissot() input is now any “xy-ish” object (matrix,
data.frame, list, length-2 vector) via the internal as_xy()
helper. The old lambda/phi positional
arguments are replaced by x.
tissot() returns a tissot_tbl
(subclassed tibble) with source and target
stored as attributes. Column names changed to: x,
y, dx_dlam, dy_dlam,
dx_dphi, dy_dphi, scale_h,
scale_k, scale_omega, scale_a,
scale_b, scale_area,
angle_deformation, convergence.
indicatrix() returns an indicatrix_list
(replaces indicatrixes class). Accepts
tissot_tbl or raw coordinates + explicit
target.
Removed: indicatrix0(), tissot0(),
.prj(), and the internal numericDeriv path.
The Jacobian is now computed directly via finite differences.
plot.indicatrix() and
plot.indicatrix_list() with:
show.circle)show.axes)show.circle and show.axes accept
TRUE, FALSE, or a named list of graphical
parameters for full customizationfill.by
(e.g. "scale_area", "angle_deformation")print() and summary() methods for
tissot_tbl.
print(), length(), and [
methods for indicatrix_list.
tissot_map() and tissot_abline() accept
explicit target argument.
as_xy() internal helper coerces diverse coordinate
inputs.
resolve_gpar() internal helper for the
logical-or-list graphical parameter pattern.
transform_xy() call.