Propagation path structure and functions. More...

#include "agenda_class.h"
#include "array.h"
#include "arts.h"
#include "interpolation.h"
#include "matpackI.h"
#include "mystring.h"

Classes
struct	Ppath
	The structure to describe a propagation path and releated quantities. More...

Typedefs
typedef Array< Ppath >	ArrayOfPpath
	An array of propagation paths. More...

Functions
void	add_za_aa (Numeric &za, Numeric &aa, const Numeric &za0, const Numeric &aa0, const Numeric &dza, const Numeric &daa)
	Adds up zenith and azimuth angles. More...

void	cart2zaaa (Numeric &za, Numeric &aa, const Numeric &dx, const Numeric &dy, const Numeric &dz)
	Converts a cartesian directional vector to zenith and azimuth. More...

void	diff_za_aa (Numeric &dza, Numeric &daa, const Numeric &za0, const Numeric &aa0, const Numeric &za, const Numeric &aa)
	Takes the difference of zenith and azimuth angles. More...

void	error_if_limb_ppath (const Ppath &ppath)
	Throws an error if ppath altitudes not are strictly increasing or decreasing. More...

void	find_tanpoint (Index &it, const Ppath &ppath)
	Identifies the tangent point of a propagation path. More...

Index	first_pos_before_altitude (const Ppath &p, const Numeric &alt)
	Determines ppath position just below an altitude. More...

Numeric	geometrical_ppc (const Numeric &r, const Numeric &za)
	Calculates the propagation path constant for pure geometrical calculations. More...

Numeric	geompath_lat_at_za (const Numeric &za0, const Numeric &lat0, const Numeric &za)
	Calculates the latitude for a given zenith angle along a geometrical propagation path. More...

Numeric	geompath_l_at_r (const Numeric &ppc, const Numeric &r)
	Calculates the length from the tangent point for the given radius. More...

Numeric	geompath_za_at_r (const Numeric &ppc, const Numeric &a_za, const Numeric &r)
	Calculates the zenith angle for a given radius along a geometrical propagation path. More...

bool	is_los_downwards (const Numeric &za, const Numeric &tilt)
	Determines if a line-of-sight is downwards compared to the angular tilt of the surface or a pressure level. More...

Numeric	plevel_angletilt (const Numeric &r, const Numeric &c)
	Calculates the angular tilt of the surface or a pressure level. More...

void	plevel_slope_2d (Numeric &c1, ConstVectorView lat_grid, ConstVectorView refellipsoid, ConstVectorView z_surf, const GridPos &gp, const Numeric &za)
	Calculates the radial slope of the surface or a pressure level for 2D. More...

void	plevel_slope_3d (Numeric &c1, Numeric &c2, ConstVectorView lat_grid, ConstVectorView lon_grid, ConstVectorView refellipsoid, ConstMatrixView z_surf, const GridPos &gp_lat, const GridPos &gp_lon, const Numeric &aa)
	Calculates the radial slope of the surface or a pressure level for 3D. More...

void	ppath_calc (Workspace &ws, Ppath &ppath, const Agenda &ppath_step_agenda, const Index &atmosphere_dim, const Vector &p_grid, const Vector &lat_grid, const Vector &lon_grid, const Tensor3 &z_field, const Vector &f_grid, const Vector &refellipsoid, const Matrix &z_surface, const Index &cloudbox_on, const ArrayOfIndex &cloudbox_limits, const Vector &rte_pos, const Vector &rte_los, const Numeric &ppath_lmax, const Numeric &ppath_lraytrace, const bool &ppath_inside_cloudbox_do, const Verbosity &verbosity)
	This is the core for the WSM ppathStepByStep. More...

void	ppath_copy (Ppath &ppath1, const Ppath &ppath2, const Index &ncopy)
	Copy the content in ppath2 to ppath1. More...

void	ppath_init_structure (Ppath &ppath, const Index &atmosphere_dim, const Index &np)
	Initiates a Ppath structure to hold the given number of points. More...

void	ppath_set_background (Ppath &ppath, const Index &case_nr)
	Sets the background field of a Ppath structure. More...

void	ppath_start_stepping (Ppath &ppath, const Index &atmosphere_dim, ConstVectorView p_grid, ConstVectorView lat_grid, ConstVectorView lon_grid, ConstTensor3View z_field, ConstVectorView refellipsoid, ConstMatrixView z_surface, const Index &cloudbox_on, const ArrayOfIndex &cloudbox_limits, const bool &outside_cloudbox, ConstVectorView rte_pos, ConstVectorView rte_los, const Verbosity &verbosity)
	Initiates a Ppath structure for calculation of a path with ppath_step. More...

void	ppath_step_geom_1d (Ppath &ppath, ConstVectorView z_field, ConstVectorView refellipsoid, const Numeric &z_surface, const Numeric &lmax)
	Calculates 1D geometrical propagation path steps. More...

void	ppath_step_geom_2d (Ppath &ppath, ConstVectorView lat_grid, ConstMatrixView z_field, ConstVectorView refellipsoid, ConstVectorView z_surface, const Numeric &lmax)
	Calculates 2D geometrical propagation path steps. More...

void	ppath_step_geom_3d (Ppath &ppath, ConstVectorView lat_grid, ConstVectorView lon_grid, ConstTensor3View z_field, ConstVectorView refellipsoid, ConstMatrixView z_surface, const Numeric &lmax)
	Calculates 3D geometrical propagation path steps. More...

void	ppath_step_refr_1d (Workspace &ws, Ppath &ppath, ConstVectorView p_grid, ConstTensor3View z_field, ConstTensor3View t_field, ConstTensor4View vmr_field, ConstVectorView f_grid, ConstVectorView refellipsoid, const Numeric &z_surface, const Numeric &lmax, const Agenda &refr_index_agenda, const String &rtrace_method, const Numeric &lraytrace)
	Calculates 1D propagation path steps including effects of refraction. More...

void	ppath_step_refr_2d (Workspace &ws, Ppath &ppath, ConstVectorView p_grid, ConstVectorView lat_grid, ConstTensor3View z_field, ConstTensor3View t_field, ConstTensor4View vmr_field, ConstVectorView f_grid, ConstVectorView refellipsoid, ConstVectorView z_surface, const Numeric &lmax, const Agenda &refr_index_agenda, const String &rtrace_method, const Numeric &lraytrace)
	Calculates 2D propagation path steps, with refraction, using a simple and fast ray tracing scheme. More...

void	ppath_step_refr_3d (Workspace &ws, Ppath &ppath, ConstVectorView p_grid, ConstVectorView lat_grid, ConstVectorView lon_grid, ConstTensor3View z_field, ConstTensor3View t_field, ConstTensor4View vmr_field, ConstVectorView f_grid, ConstVectorView refellipsoid, ConstMatrixView z_surface, const Numeric &lmax, const Agenda &refr_index_agenda, const String &rtrace_method, const Numeric &lraytrace)
	Calculates 3D propagation path steps, with refraction, using a simple and fast ray tracing scheme. More...

Index	ppath_what_background (const Ppath &ppath)
	Returns the case number for the radiative background. More...

void	resolve_lon (Numeric &lon, const Numeric &lon5, const Numeric &lon6)
	Resolves which longitude angle that shall be used. More...

void	zaaa2cart (Numeric &dx, Numeric &dy, Numeric &dz, const Numeric &za, const Numeric &aa)
	Converts zenith and azimuth angles to a cartesian unit vector. More...

Variables
const Numeric	POLELAT = 90 - 1e-8
	Size of north and south poles. More...

const Numeric	ANGTOL = 1e-6
	Width of zenith and nadir directions. More...

Detailed Description

Propagation path structure and functions.

Author: Patrick Eriksson patri.nosp@m.ck.e.nosp@m.rikss.nosp@m.on@c.nosp@m.halme.nosp@m.rs.s.nosp@m.e

Date: 2002-05-02

This file contains the definition of the Ppath structure and the functions in ppath.cc that are of interest elsewhere.

Definition in file ppath.h.

Typedef Documentation

◆ ArrayOfPpath

typedef Array<Ppath> ArrayOfPpath

An array of propagation paths.

Definition at line 90 of file ppath.h.

Function Documentation

◆ add_za_aa()

void add_za_aa	(	Numeric &	za,
		Numeric &	aa,
		const Numeric &	za0,
		const Numeric &	aa0,
		const Numeric &	dza,
		const Numeric &	daa
	)

Adds up zenith and azimuth angles.

Adds (dza,daa) to (za0,aa0), assuming that a unit changes in za and aa are equal where (dza,daa)=(0,0).

Parameters

[out]	za	End zenith angle
[out]	aa	End azimuth angle
[in]	za0	Start zenith angle
[in]	aa0	Start azimuth angle
[in]	dza	Change in zenith angle
[in]	daa	Change in azimuth angle

Author: Patrick Eriksson

Date: 2018-12-19

Definition at line 406 of file ppath.cc.

References zaaa2cart().

Referenced by AddZaAa(), iyb_calc_body(), and Test().

◆ cart2zaaa()

void cart2zaaa	(	Numeric &	za,
		Numeric &	aa,
		const Numeric &	dx,
		const Numeric &	dy,
		const Numeric &	dz
	)

Converts a cartesian directional vector to zenith and azimuth.

This function and the sister function cart2zaaa handle transformation of line-of-sights. This in contrast to the sph/poslos functions that handles positions, or combinations of positions and line-of-sight.

The cartesian coordinate system used for these two functions can be defined as z : za = 0 x : za=90, aa=0 y : za=90, aa=90

Parameters

[out]	za	LOS zenith angle at observation position.
[out]	aa	LOS azimuth angle at observation position.
[in]	dx	x-part of LOS unit vector.
[in]	dy	y-part of LOS unit vector.
[in]	dz	z-part of LOS unit vector.

Author: Patrick Eriksson

Date: 2009-10-02

Definition at line 312 of file ppath.cc.

References dx, RAD2DEG, and sqrt().

Referenced by adjust_los(), and specular_losCalc().

◆ diff_za_aa()

void diff_za_aa	(	Numeric &	dza,
		Numeric &	daa,
		const Numeric &	za0,
		const Numeric &	aa0,
		const Numeric &	za,
		const Numeric &	aa
	)

Takes the difference of zenith and azimuth angles.

Takes the difference between a set of angles (za,aa) and a reference direction (za0,aa0). That is, this function is the "inverse" of add_za_aa.

Parameters

[out]	dza	Change in zenith angle
[out]	daa	Change in azimuth angle
[in]	za0	Zenith angle of reference direction
[in]	aa0	Azimuth angle of reference direction
[in]	za	Zenith angle of second direction
[in]	aa	Azimuth angle of second direction

Author: Patrick Eriksson

Date: 2018-12-19

Definition at line 444 of file ppath.cc.

References zaaa2cart().

Referenced by DiffZaAa(), and Test().

◆ error_if_limb_ppath()

void error_if_limb_ppath ( const Ppath & ppath )

Throws an error if ppath altitudes not are strictly increasing or decreasing.

Parameters

[in] ppath Propagation path structure.

Author: Patrick Eriksson

Date: 2018-03-07

Definition at line 555 of file ppath.cc.

References ARTS::Var::Ppath::pos(), ARTS::Var::ppath(), and sign().

Referenced by iyIndependentBeamApproximation(), and yActive().

◆ find_tanpoint()

void find_tanpoint	(	Index &	it,
		const Ppath &	ppath
	)

Identifies the tangent point of a propagation path.

The tangent points is defined as the point with the lowest altitude.

The index of the tangent point is determined. If no tangent point is found, the index is set to -1.

Parameters

[out]	it	Index of tangent point
[in]	ppath	Propagation path structure.

Author: Patrick Eriksson

Date: 2012-04-07

Definition at line 525 of file ppath.cc.

References ARTS::Var::Ppath::pos(), and ARTS::Var::ppath().

Referenced by defocusing_sat2sat(), TangentPointExtract(), and TangentPointPrint().

◆ first_pos_before_altitude()

Index first_pos_before_altitude	(	const Ppath &	p,
		const Numeric &	alt
	)

Determines ppath position just below an altitude.

Returns -1 if the selected altitude is not passed.

Parameters

[in]	ppath	Propagation path structure.
[in]	alt	Altitude

Returns: Index of found altitude

Author: Richard Larsson

Date: 20??-??-??

Definition at line 537 of file ppath.cc.

References Ppath::np, and Ppath::pos.

Referenced by ppathCalcFromAltitude().

◆ geometrical_ppc()

Numeric geometrical_ppc	(	const Numeric &	r,
		const Numeric &	za
	)

Calculates the propagation path constant for pure geometrical calculations.

Both positive and negative zenith angles are handled.

Parameters

[in]	r	Radius of the sensor position.
[in]	za	Zenith angle of the sensor line-of-sight.

Returns: Path constant.

Author: Patrick Eriksson

Date: 2002-05-17

Definition at line 96 of file ppath.cc.

References abs, and DEG2RAD.

Referenced by ppath_start_stepping(), ppath_step_geom_1d(), ppath_step_geom_2d(), ppath_step_geom_3d(), raytrace_1d_linear_basic(), raytrace_2d_linear_basic(), and raytrace_3d_linear_basic().

◆ geompath_l_at_r()

Numeric geompath_l_at_r	(	const Numeric &	ppc,
		const Numeric &	r
	)

Calculates the length from the tangent point for the given radius.

The tangent point is either real or imaginary depending on the zenith angle of the sensor. See geometrical_tangent_radius.

Parameters

[in]	ppc	Propagation path constant.
[in]	r	Radius of the point of concern.

Returns: Length along the path from the tangent point. Always >= 0.

Author: Patrick Eriksson

Date: 2002-05-20

Definition at line 158 of file ppath.cc.

References RTOL, and sqrt().

Referenced by cart2poslos(), geompath_from_r1_to_r2(), ppath_start_stepping(), r_crossing_2d(), raytrace_1d_linear_basic(), and raytrace_2d_linear_basic().

◆ geompath_lat_at_za()

Numeric geompath_lat_at_za	(	const Numeric &	za0,
		const Numeric &	lat0,
		const Numeric &	za
	)

Calculates the latitude for a given zenith angle along a geometrical propagation path.

Positive and negative zenith angles are handled. A positive zenith angle means a movement towards higher latitudes.

Parameters

[in]	za0	The zenith angle of the starting point.
[in]	lat0	The latitude of the starting point.
[in]	za	The zenith angle of the second point.

Returns: The latitude of the second point.

Author: Patrick Eriksson

Date: 2002-05-17

Definition at line 148 of file ppath.cc.

References abs.

Referenced by geompath_from_r1_to_r2(), ppath_start_stepping(), r_crossing_2d(), raytrace_1d_linear_basic(), and raytrace_2d_linear_basic().

◆ geompath_za_at_r()

Numeric geompath_za_at_r	(	const Numeric &	ppc,
		const Numeric &	a_za,
		const Numeric &	r
	)

Calculates the zenith angle for a given radius along a geometrical propagation path.

For downlooking cases, the two points must be on the same side of the tangent point.

Both positive and negative zenith angles are handled.

Parameters

[in]	ppc	Propagation path constant.
[in]	a_za	A zenith angle along the path on the same side of the tangent point as the point of interest.
[in]	r	Radius of the point of interest.

Returns: Zenith angle at the point of interest.

Author: Patrick Eriksson

Date: 2002-05-17

Definition at line 103 of file ppath.cc.

References abs, RAD2DEG, and RTOL.

Referenced by geompath_from_r1_to_r2(), ppath_start_stepping(), r_crossing_2d(), raytrace_1d_linear_basic(), raytrace_2d_linear_basic(), and VectorZtanToZa1D().

◆ is_los_downwards()

bool is_los_downwards	(	const Numeric &	za,
		const Numeric &	tilt
	)

Determines if a line-of-sight is downwards compared to the angular tilt of the surface or a pressure level.

For example, this function can be used to determine if the line-of-sight goes into the surface for a starting point exactly on the surface radius.

As the radius of the surface and pressure levels varies as a function of latitude, it is not clear if a zenith angle of 90 is above or below e.g. the surface.

Parameters

[in]	za	Zenith angle of line-of-sight.
[in]	tilt	Angular tilt of the surface or the pressure level (as returned by plevel_angletilt)

Returns: Boolean that is true if LOS is downwards.

Author: Patrick Eriksson

Date: 2002-06-03

Definition at line 638 of file ppath.cc.

References abs.

Referenced by ppath_start_2d(), and ppath_start_stepping().

◆ plevel_angletilt()

Numeric plevel_angletilt	(	const Numeric &	r,
		const Numeric &	c
	)

Calculates the angular tilt of the surface or a pressure level.

Note that the tilt value is a local value. The tilt for a constant slope value, is different for different radii.

Parameters

[in]	r	The radius for the level at the point of interest.
[in]	c1	The radial slope, as returned by e.g. plevel_slope_2d.

Returns: The angular tilt.

Author: Patrick Eriksson

Date: 2002-06-03

Definition at line 632 of file ppath.cc.

References RAD2DEG.

Referenced by ppath_start_2d(), ppath_start_3d(), ppath_start_stepping(), and specular_losCalc().

◆ plevel_slope_2d()

void plevel_slope_2d	(	Numeric &	c1,
		ConstVectorView	lat_grid,
		ConstVectorView	refellipsoid,
		ConstVectorView	z_surf,
		const GridPos &	gp,
		const Numeric &	za
	)

Calculates the radial slope of the surface or a pressure level for 2D.

The radial slope is here the derivative of the radius with respect to the latitude. The unit is accordingly m/degree.

Note that the radius is defined to change linearly between grid points, and the slope is constant between to points of the latitude grid. The radius can inside the grid range be expressed as r = r0(lat0) + c1*(lat-lat0) .

Note also that the slope is always calculated with respect to increasing latitudes, independently of the zenith angle. The zenith angle is only used to determine which grid range that is of interest when the position is exactly on top of a grid point.

Parameters

[out]	c1	The radial slope [m/degree]
[in]	lat_grid	The latitude grid.
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surf	Geometrical altitude of the surface, or the pressure level of interest, for the latitide dimension
[in]	gp	Latitude grid position for the position of interest
[in]	za	LOS zenith angle.

Author: Patrick Eriksson

Date: 2002-06-03

Definition at line 595 of file ppath.cc.

References gridpos2gridrange(), ARTS::Var::lat_grid(), refell2r(), and ARTS::Var::refellipsoid().

Referenced by ppath_start_2d(), ppath_start_stepping(), and specular_losCalc().

◆ plevel_slope_3d()

void plevel_slope_3d	(	Numeric &	c1,
		Numeric &	c2,
		ConstVectorView	lat_grid,
		ConstVectorView	lon_grid,
		ConstVectorView	refellipsoid,
		ConstMatrixView	z_surf,
		const GridPos &	gp_lat,
		const GridPos &	gp_lon,
		const Numeric &	aa
	)

Calculates the radial slope of the surface or a pressure level for 3D.

For 2D the radius can be expressed as r = r0 + c1*dalpha, where alpha is the latitude. The radius is here for 3D expressed as a second order polynomial: r = r0 + c1*dalpha + c2*dalpha^2, where alpha is the angular change (in degrees) along the great circle along the given azimuth angle.

Parameters

[out]	c1	See above. Unit is m/degree.
[out]	c2	See above. Unit is m/degree^2.
[in]	lat1	Lower latitude of grid cell.
[in]	lat3	Upper latitude of grid cell.
[in]	lon5	Lower longitude of grid cell.
[in]	lon6	Upper longitude of grid cell.
[in]	r15	Radius at crossing of lat1 and lon5.
[in]	r35	Radius at crossing of lat3 and lon5.
[in]	r36	Radius at crossing of lat3 and lon6.
[in]	r16	Radius at crossing of lat1 and lon6.
[in]	lat	Latitude for which slope shall be determined.
[in]	lon	Longitude for which slope shall be determined.
[in]	aa	Azimuth angle for which slope shall be determined.

Author: Patrick Eriksson

Date: 2002-12-30

For 2D where the radius can be expressed as r = r0 + c1*dalpha, where alpha is the latitude. The radius is here for 3D expressed as a second order polynomial: r = r0 + c1*dalpha + c2*dalpha^2, where alpha is the angular change (in degrees) along the great circle along the given azimuth angle.

For a point exactly on a grid value it is not clear if it is the range below or above that is of interest. The azimuth angle is used to resolve such cases.

Parameters

[out]	c1	See above. Unit is m/degree.
[out]	c2	See above. Unit is m/degree^2.
[in]	lat_grid	The latitude grid.
[in]	lon_grid	The longitude grid.
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surf	Geometrical altitude of the surface, or the pressure level of interest.
[in]	gp_lat	Latitude grid position for the position of interest.
[in]	gp_lon	Longitude grid position for the position of interest.
[in]	aa	Azimuth angle.

Author: Patrick Eriksson

Date: 2002-06-03

Definition at line 1162 of file ppath.cc.

References abs, gridpos2gridrange(), interp(), interpweights(), is_lon_cyclic(), ARTS::Var::lat(), ARTS::Var::lat_grid(), ARTS::Var::lon(), ARTS::Var::lon_grid(), plevel_slope_3d(), POLELAT, refell2r(), and ARTS::Var::refellipsoid().

◆ ppath_calc()

void ppath_calc	(	Workspace &	ws,
		Ppath &	ppath,
		const Agenda &	ppath_step_agenda,
		const Index &	atmosphere_dim,
		const Vector &	p_grid,
		const Vector &	lat_grid,
		const Vector &	lon_grid,
		const Tensor3 &	z_field,
		const Vector &	f_grid,
		const Vector &	refellipsoid,
		const Matrix &	z_surface,
		const Index &	cloudbox_on,
		const ArrayOfIndex &	cloudbox_limits,
		const Vector &	rte_pos,
		const Vector &	rte_los,
		const Numeric &	ppath_lmax,
		const Numeric &	ppath_lraytrace,
		const bool &	ppath_inside_cloudbox_do,
		const Verbosity &	verbosity
	)

This is the core for the WSM ppathStepByStep.

This function takes mainly the same input as ppathStepByStep (that is, those input arguments are the WSV with the same name).

Parameters

[in]	ws	Current Workspace
[in]	ppath	Output: A Ppath structure
[in]	ppath_step_agenda	As the WSM with the same name.
[in]	atmosphere_dim	The atmospheric dimensionality.
[in]	p_grid	The pressure grid.
[in]	lat_grid	The latitude grid.
[in]	lon_grid	The longitude grid.
[in]	z_field	As the WSM with the same name.
[in]	f_grid	As the WSM with the same name.
[in]	refellipsoid	As the WSM with the same name.
[in]	z_surface	Surface altitude.
[in]	cloudbox_on	Flag to activate the cloud box.
[in]	cloudbox_limits	Index limits of the cloud box.
[in]	rte_pos	The position of the sensor.
[in]	rte_los	The line-of-sight of the sensor.
[in]	ppath_lmax	As the WSM with the same name.
[in]	ppath_lraytrace	As the WSM with the same name.
[in]	ppath_inside_cloudbox_do	As the WSM with the same name.

Author: Patrick Eriksson

Date: 2003-01-08

Definition at line 5206 of file ppath.cc.

References abs, ARTS::Var::atmosphere_dim(), chk_rte_los(), chk_rte_pos(), ARTS::Var::cloudbox_limits(), ARTS::Var::cloudbox_on(), ARTS::Var::f_grid(), fractional_gp(), gridpos(), is_gridpos_at_index_i(), joker, ARTS::Var::lat_grid(), ARTS::Var::lon_grid(), Array< base >::nelem(), ARTS::Var::p_grid(), ARTS::Var::Ppath::pos(), ARTS::Var::ppath(), ppath_copy(), ppath_init_structure(), ARTS::Var::ppath_inside_cloudbox_do(), ARTS::Var::ppath_lmax(), ARTS::Var::ppath_lraytrace(), ppath_set_background(), ppath_start_stepping(), ARTS::Var::ppath_step(), ARTS::Var::ppath_step_agenda(), ppath_step_agendaExecute(), ppath_what_background(), ARTS::Var::refellipsoid(), ARTS::Var::rte_los(), ARTS::Var::rte_pos(), ARTS::Var::verbosity(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by defocusing_general_sub(), defocusing_sat2sat(), ppathFromRtePos2(), and ppathStepByStep().

◆ ppath_copy()

void ppath_copy	(	Ppath &	ppath1,
		const Ppath &	ppath2,
		const Index &	ncopy
	)

Copy the content in ppath2 to ppath1.

The ppath1 structure must be allocated before calling the function. The structure can be allocated to hold more points than found in ppath2. The data of ppath2 is placed in the first positions of ppath1.

Parameters

[in]	ppath1	Output: Ppath structure.
[in]	ppath2	The ppath structure to be copied.
[in]	ncopy	Number of points in ppath2 to copy. If set to negative, the number is set to ppath2.np.

Author: Patrick Eriksson

Date: 2002-07-03

Definition at line 1515 of file ppath.cc.

References Ppath::background, Ppath::constant, Ppath::dim, Ppath::end_los, Ppath::end_lstep, Ppath::end_pos, Ppath::gp_lat, Ppath::gp_lon, Ppath::gp_p, gridpos_copy(), joker, Ppath::los, Ppath::lstep, Ppath::ngroup, Ppath::np, Ppath::nreal, Ppath::pos, Ppath::r, Ppath::start_los, Ppath::start_lstep, and Ppath::start_pos.

Referenced by ppath_append(), ppath_calc(), and ppathFromRtePos2().

◆ ppath_init_structure()

void ppath_init_structure	(	Ppath &	ppath,
		const Index &	atmosphere_dim,
		const Index &	np
	)

Initiates a Ppath structure to hold the given number of points.

The background field is set to background case 0. The constant field is set to -1. The refraction field is set to 0.

The length of the lstep field is set to np-1.

Parameters

[in]	ppath	Output: A Ppath structure.
[in]	atmosphere_dim	The atmospheric dimensionality.
[in]	np	Number of points of the path.

Author: Patrick Eriksson

Date: 2002-05-17

Definition at line 1426 of file ppath.cc.

References ARTS::Var::atmosphere_dim(), max, ARTS::Var::Ppath::pos(), ARTS::Var::ppath(), and ppath_set_background().

Referenced by cloud_ppath_update1D(), cloud_ppath_update1D_noseq(), cloud_ppath_update3D(), ppath_append(), ppath_calc(), ppath_end_1d(), ppath_end_2d(), ppath_end_3d(), ppath_start_stepping(), ppathFromRtePos2(), and ppathPlaneParallel().

◆ ppath_set_background()

void ppath_set_background	(	Ppath &	ppath,
		const Index &	case_nr
	)

Sets the background field of a Ppath structure.

The different background cases have a number coding to simplify a possible change of the strings and checking of the what case that is valid.

The case numbers are:
0. Unvalid.

Space.
The surface.
The cloud box boundary.
The interior of the cloud box.

Parameters

[in]	ppath	Output: A Ppath structure.
[in]	case_nr	Case number (see above)

Author: Patrick Eriksson

Date: 2002-05-17

Definition at line 1467 of file ppath.cc.

References ARTS::Var::ppath().

Referenced by ppath_calc(), ppath_end_1d(), ppath_end_2d(), ppath_end_3d(), ppath_init_structure(), ppath_start_stepping(), ppathFromRtePos2(), and ppathPlaneParallel().

◆ ppath_start_stepping()

void ppath_start_stepping	(	Ppath &	ppath,
		const Index &	atmosphere_dim,
		ConstVectorView	p_grid,
		ConstVectorView	lat_grid,
		ConstVectorView	lon_grid,
		ConstTensor3View	z_field,
		ConstVectorView	refellipsoid,
		ConstMatrixView	z_surface,
		const Index &	cloudbox_on,
		const ArrayOfIndex &	cloudbox_limits,
		const bool &	outside_cloudbox,
		ConstVectorView	rte_pos,
		ConstVectorView	rte_los,
		const Verbosity &	verbosity
	)

Initiates a Ppath structure for calculation of a path with ppath_step.

The function performs two main tasks. As mentioned above, it initiates a Ppath structure (a), but it also checks that the end point of the path is at an allowed location (b).

(a): The Ppath structure is set to hold the position and LOS of the last point of the path inside the atmosphere. This point is either the sensor position, or the point where the path leaves the model atmosphere. If the path is totally outside the atmosphere, no point is put into the structure. If the (practical) end and start points are identical, such as when the sensor is inside the cloud box, the background field is set.

(b): If it is found that the end point of the path is at an illegal position a detailed error message is given. Not allowed cases are:

The sensor is placed below surface level.
For 2D and 3D, the path leaves the model atmosphere at a latitude or longitude end face.
For 2D and 3D, the path is totally outside the atmosphere and the latitude and longitude of the tangent point is outside the range of the corresponding grids.

All input variables are identical with the WSV with the same name. The output variable is here called ppath for simplicity, but is in fact ppath_step.

Parameters

[in]	ppath	Output: A Ppath structure.
[in]	atmosphere_dim	The atmospheric dimensionality.
[in]	p_grid	The pressure grid.
[in]	lat_grid	The latitude grid.
[in]	lon_grid	The longitude grid.
[in]	z_field	The field of geometrical altitudes.
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surface	Surface altitude.
[in]	cloudbox_on	Flag to activate the cloud box.
[in]	cloudbox_limits	Index limits of the cloud box.
[in]	ppath_inside_cloudbox_do	As the WSV with the same name.
[in]	rte_pos	The position of the sensor.
[in]	rte_los	The line-of-sight of the sensor.

Author: Patrick Eriksson

Date: 2002-05-17

Definition at line 4495 of file ppath.cc.

References abs, ARTS::Var::atmosphere_dim(), cart2poslos(), ARTS::Var::cloudbox_limits(), ARTS::Var::cloudbox_on(), CREATE_OUT1, DEBUG_ONLY, dx, fractional_gp(), geometrical_ppc(), geompath_l_at_r(), geompath_lat_at_za(), geompath_za_at_r(), gridpos(), gridpos_check_fd(), gridpos_copy(), interp(), interpweights(), is_los_downwards(), joker, L_NOT_FOUND, LACC, ARTS::Var::lat_grid(), ARTS::Var::lon_grid(), ARTS::Var::p_grid(), plevel_angletilt(), plevel_slope_2d(), plevel_slope_3d(), ARTS::Var::Ppath::pos(), poslos2cart(), ARTS::Var::ppath(), ppath_init_structure(), ARTS::Var::ppath_inside_cloudbox_do(), ppath_set_background(), r_crossing_2d(), r_crossing_3d(), refell2d(), refell2r(), ARTS::Var::refellipsoid(), resolve_lon(), ARTS::Var::rte_los(), ARTS::Var::rte_pos(), rte_pos2gridpos(), RTOL, ARTS::Var::x(), ARTS::Var::y(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by mcPathTraceRadar(), and ppath_calc().

◆ ppath_step_geom_1d()

void ppath_step_geom_1d	(	Ppath &	ppath,
		ConstVectorView	z_field,
		ConstVectorView	refellipsoid,
		const Numeric &	z_surface,
		const Numeric &	lmax
	)

Calculates 1D geometrical propagation path steps.

This is the core function to determine 1D propagation path steps by pure geometrical calculations. Path points are included for crossings with the grids, tangent points and points of intersection with the surface. In addition, points are included in the propgation path to ensure that the distance along the path between the points does not exceed the selected maximum length (lmax). If lmax is <= 0, this means that no length criterion shall be applied.

Note that the input variables are here compressed to only hold data for a 1D atmosphere. For example, z_field is z_field(:,0,0).

For more information read the chapter on propagation paths in AUG.

Parameters

[in]	ppath	Output: A Ppath structure.
[in]	z_field	Geometrical altitudes corresponding to p_grid.
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surface	Surface altitude.
[in]	lmax	Maximum allowed length between the path points.

Author: Patrick Eriksson

Date: 2002-05-20

Definition at line 2372 of file ppath.cc.

References do_gridrange_1d(), geometrical_ppc(), ConstVectorView::nelem(), ARTS::Var::ppath(), ppath_end_1d(), ppath_start_1d(), ARTS::Var::refellipsoid(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by ppath_stepGeometric().

◆ ppath_step_geom_2d()

void ppath_step_geom_2d	(	Ppath &	ppath,
		ConstVectorView	lat_grid,
		ConstMatrixView	z_field,
		ConstVectorView	refellipsoid,
		ConstVectorView	z_surface,
		const Numeric &	lmax
	)

Calculates 2D geometrical propagation path steps.

Works as the same function for 1D, despite that some input arguments are of different type.

Parameters

[in]	ppath	Output: A Ppath structure.
[in]	lat_grid	Latitude grid.
[in]	z_field	Geometrical altitudes
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surface	Surface altitudes.
[in]	lmax	Maximum allowed length between the path points.

Author: Patrick Eriksson

Date: 2002-07-03

Definition at line 2736 of file ppath.cc.

References do_gridcell_2d_byltest(), geometrical_ppc(), ARTS::Var::lat_grid(), ConstVectorView::nelem(), ARTS::Var::ppath(), ppath_end_2d(), ppath_start_2d(), ARTS::Var::refellipsoid(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by ppath_stepGeometric().

◆ ppath_step_geom_3d()

void ppath_step_geom_3d	(	Ppath &	ppath,
		ConstVectorView	lat_grid,
		ConstVectorView	lon_grid,
		ConstTensor3View	z_field,
		ConstVectorView	refellipsoid,
		ConstMatrixView	z_surface,
		const Numeric &	lmax
	)

Calculates 3D geometrical propagation path steps.

Works as the same function for 1D despite that some input arguments are of different type.

Parameters

[in]	ppath	Output: A Ppath structure.
[in]	lat_grid	Latitude grid.
[in]	lon_grid	Longitude grid.
[in]	z_field	Geometrical altitudes
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surface	Surface altitudes.
[in]	lmax	Maximum allowed length between the path points.

Author: Patrick Eriksson

Date: 2002-12-30

Definition at line 3270 of file ppath.cc.

References do_gridcell_3d_byltest(), geometrical_ppc(), ARTS::Var::lat_grid(), ARTS::Var::lon_grid(), ConstVectorView::nelem(), ARTS::Var::ppath(), ppath_end_3d(), ppath_start_3d(), ARTS::Var::refellipsoid(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by ppath_stepGeometric().

◆ ppath_step_refr_1d()

void ppath_step_refr_1d	(	Workspace &	ws,
		Ppath &	ppath,
		ConstVectorView	p_grid,
		ConstTensor3View	z_field,
		ConstTensor3View	t_field,
		ConstTensor4View	vmr_field,
		ConstVectorView	f_grid,
		ConstVectorView	refellipsoid,
		const Numeric &	z_surface,
		const Numeric &	lmax,
		const Agenda &	refr_index_agenda,
		const String &	rtrace_method,
		const Numeric &	lraytrace
	)

Calculates 1D propagation path steps including effects of refraction.

This function works as the function ppath_step_geom_1d but considers also refraction. The upper length of the ray tracing steps is set by the argument lraytrace. This argument controls only the internal calculations. The maximum distance between the path points is still determined by lmax.

Parameters

[in,out]	ws	Current Workspace
[out]	ppath	A Ppath structure.
[in]	p_grid	Pressure grid.
[in]	z_field	As the WSV with the same name.
[in]	t_field	As the WSV with the same name.
[in]	vmr_field	As the WSV with the same name.
[in]	f_grid	As the WSV with the same name.
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surface	Surface altitude (1D).
[in]	lmax	Maximum allowed length between the path points.
[in]	refr_index_air_agenda	The WSV with the same name.
[in]	rtrace_method	String giving which ray tracing method to use. See the function for options.
[in]	lraytrace	Maximum allowed length for ray tracing steps.

Author: Patrick Eriksson

Date: 2002-11-26

Definition at line 3576 of file ppath.cc.

References ARTS::Var::f_grid(), get_refr_index_1d(), joker, Array< base >::nelem(), ARTS::Var::p_grid(), ARTS::Var::ppath(), ppath_end_1d(), ppath_start_1d(), raytrace_1d_linear_basic(), ARTS::Var::refellipsoid(), ARTS::Var::refr_index_air(), ARTS::Var::refr_index_air_agenda(), ARTS::Var::refr_index_air_group(), refraction_ppc(), ARTS::Var::t_field(), ARTS::Var::vmr_field(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by ppath_stepRefractionBasic().

◆ ppath_step_refr_2d()

void ppath_step_refr_2d	(	Workspace &	ws,
		Ppath &	ppath,
		ConstVectorView	p_grid,
		ConstVectorView	lat_grid,
		ConstTensor3View	z_field,
		ConstTensor3View	t_field,
		ConstTensor4View	vmr_field,
		ConstVectorView	f_grid,
		ConstVectorView	refellipsoid,
		ConstVectorView	z_surface,
		const Numeric &	lmax,
		const Agenda &	refr_index_agenda,
		const String &	rtrace_method,
		const Numeric &	lraytrace
	)

Calculates 2D propagation path steps, with refraction, using a simple and fast ray tracing scheme.

Works as the same function for 1D despite that some input arguments are of different type.

Parameters

[in,out]	ws	Current Workspace
[out]	ppath	A Ppath structure.
[in]	p_grid	Pressure grid.
[in]	lat_grid	Latitude grid.
[in]	z_field	As the WSV with the same name.
[in]	t_field	As the WSV with the same name.
[in]	vmr_field	As the WSV with the same name.
[in]	f_grid	As the WSV with the same name.
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surface	Surface altitudes.
[in]	lmax	Maximum allowed length between the path points.
[in]	refr_index_air_agenda	The WSV with the same name.
[in]	rtrace_method	String giving which ray tracing method to use. See the function for options.
[in]	lraytrace	Maximum allowed length for ray tracing steps.

Author: Patrick Eriksson

Date: 2002-12-02

Definition at line 3920 of file ppath.cc.

References ARTS::Var::f_grid(), joker, ARTS::Var::lat_grid(), Array< base >::nelem(), ARTS::Var::p_grid(), ARTS::Var::ppath(), ppath_end_2d(), ppath_start_2d(), raytrace_2d_linear_basic(), ARTS::Var::refellipsoid(), ARTS::Var::refr_index_air_agenda(), ARTS::Var::t_field(), ARTS::Var::vmr_field(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by ppath_stepRefractionBasic().

◆ ppath_step_refr_3d()

void ppath_step_refr_3d	(	Workspace &	ws,
		Ppath &	ppath,
		ConstVectorView	p_grid,
		ConstVectorView	lat_grid,
		ConstVectorView	lon_grid,
		ConstTensor3View	z_field,
		ConstTensor3View	t_field,
		ConstTensor4View	vmr_field,
		ConstVectorView	f_grid,
		ConstVectorView	refellipsoid,
		ConstMatrixView	z_surface,
		const Numeric &	lmax,
		const Agenda &	refr_index_agenda,
		const String &	rtrace_method,
		const Numeric &	lraytrace
	)

Calculates 3D propagation path steps, with refraction, using a simple and fast ray tracing scheme.

Works as the same function for 1D despite that some input arguments are of different type.

Parameters

[in,out]	ws	Current Workspace
[out]	ppath	A Ppath structure.
[in]	p_grid	Pressure grid.
[in]	lat_grid	Latitude grid.
[in]	lon_grid	Longitude grid.
[in]	z_field	Geometrical altitudes.
[in]	t_field	Atmospheric temperatures.
[in]	vmr_field	VMR values.
[in]	f_grid	As the WSV with the same name.
[in]	refellipsoid	As the WSV with the same name.
[in]	z_surface	Surface altitudes.
[in]	lmax	Maximum allowed length between the path points.
[in]	refr_index_air_agenda	The WSV with the same name.
[in]	rtrace_method	String giving which ray tracing method to use. See the function for options.
[in]	lraytrace	Maximum allowed length for ray tracing steps.

Author: Patrick Eriksson

Date: 2003-01-08

Definition at line 4335 of file ppath.cc.

References ARTS::Var::f_grid(), ARTS::Var::lat_grid(), ARTS::Var::lon_grid(), Array< base >::nelem(), ARTS::Var::p_grid(), ARTS::Var::ppath(), ppath_end_3d(), ppath_start_3d(), raytrace_3d_linear_basic(), ARTS::Var::refellipsoid(), ARTS::Var::refr_index_air_agenda(), ARTS::Var::t_field(), ARTS::Var::vmr_field(), ARTS::Var::z_field(), and ARTS::Var::z_surface().

Referenced by ppath_stepRefractionBasic().

◆ ppath_what_background()

Index ppath_what_background ( const Ppath & ppath )

Returns the case number for the radiative background.

See further the function ppath_set_background.

Parameters

[in] ppath A Ppath structure.

Returns: The case number.

Author: Patrick Eriksson

Date: 2002-05-17

Definition at line 1494 of file ppath.cc.

References ARTS::Var::ppath().

Referenced by defocusing_general_sub(), defocusing_sat2sat(), get_iy_of_background(), iyActiveSingleScat(), iyActiveSingleScat2(), iyEmissionStandard(), iyEmissionStandardSequential(), iyHybrid(), iyHybrid2(), iyTransmissionStandard(), mcPathTraceRadar(), ppath_append(), ppath_calc(), ppath_stepGeometric(), ppath_stepRefractionBasic(), and ppathFromRtePos2().

◆ resolve_lon()

void resolve_lon	(	Numeric &	lon,
		const Numeric &	lon5,
		const Numeric &	lon6
	)

Resolves which longitude angle that shall be used.

Longitudes are allowed to vary between -360 and 360 degress, while the inverse trigonomtric functions returns values between -180 and 180. This function determines if the longitude shall be shifted -360 or +360 to fit the longitudes set by the user.

The argument lon as input is a value calculated by some inverse trigonometric function. The arguments lon5 and lon6 are the lower and upper limit for the probable range for lon. The longitude lon* will be shifted with -360 or +360 degrees if lon is significantly outside lon5 and lon6. No error is given if it is not possible to obtain a value between lon5 and lon6.

Parameters

[in,out]	lon	Longitude, possible shifted when returned.
[in]	lon5	Lower limit of probable range for lon.
[in]	lon6	Upper limit of probable range for lon

Author: Patrick Eriksson

Date: 2003-01-05

Definition at line 515 of file ppath.cc.

References ARTS::Var::lon().

Referenced by do_gridcell_3d_byltest(), ppath_start_stepping(), raytrace_3d_linear_basic(), and surfaceFastem().

◆ zaaa2cart()

void zaaa2cart	(	Numeric &	dx,
		Numeric &	dy,
		Numeric &	dz,
		const Numeric &	za,
		const Numeric &	aa
	)

Converts zenith and azimuth angles to a cartesian unit vector.

This function and the sister function cart2zaaa handles transformation of line-of-sights. This in contrast to the sph/poslos functions that handles positions, or combinations of positions and line-of-sight.

The cartesian coordinate system used for these two functions can be defined as z : za = 0 x : za=90, aa=0 y : za=90, aa=90

Parameters

[out]	dx	x-part of LOS unit vector.
[out]	dy	y-part of LOS unit vector.
[out]	dz	z-part of LOS unit vector.
[in]	za	LOS zenith angle at observation position.
[in]	aa	LOS azimuth angle at observation position.

Author: Patrick Eriksson

Date: 2009-10-02

Definition at line 347 of file ppath.cc.

References DEG2RAD, and dx.

Referenced by add_za_aa(), adjust_los(), diff_za_aa(), and specular_losCalc().

Variable Documentation

◆ ANGTOL

const Numeric ANGTOL = 1e-6

Width of zenith and nadir directions.

This variable defines how much zenith and azimuth angles can deviate from 0, 90 and 180 degrees, but still be treated to be 0, 90 or 180. For example, an azimuth angle of 180-0.999*ANGTOL will be treated as a strictly southward observation. However, the angles are not allowed to go outside their defined range. This means, for example, that values above 180 are never allowed.

Definition at line 108 of file ppath.h.

Referenced by cart2pol(), cart2poslos(), cart2sph(), do_gridcell_2d_byltest(), do_gridcell_3d_byltest(), geompath_from_r1_to_r2(), plevel_crossing_2d(), r_crossing_3d(), and raytrace_3d_linear_basic().

◆ POLELAT

const Numeric POLELAT = 90 - 1e-8

Size of north and south poles.

Latitudes with an absolute value > POLELAT are considered to be on the south or north pole for 3D.

Definition at line 97 of file ppath.h.

Referenced by cart2poslos(), cart2sph(), do_gridcell_3d_byltest(), plevel_slope_3d(), poslos2cart(), and ppath_end_3d().

Classes

Typedefs

Functions

Variables

Detailed Description

Typedef Documentation

◆ ArrayOfPpath

Function Documentation

◆ add_za_aa()

◆ cart2zaaa()

◆ diff_za_aa()

◆ error_if_limb_ppath()

◆ find_tanpoint()

◆ first_pos_before_altitude()

◆ geometrical_ppc()

◆ geompath_l_at_r()

◆ geompath_lat_at_za()

◆ geompath_za_at_r()

◆ is_los_downwards()

◆ plevel_angletilt()

◆ plevel_slope_2d()

◆ plevel_slope_3d()

◆ ppath_calc()

◆ ppath_copy()

◆ ppath_init_structure()

◆ ppath_set_background()

◆ ppath_start_stepping()

◆ ppath_step_geom_1d()

◆ ppath_step_geom_2d()

◆ ppath_step_geom_3d()

◆ ppath_step_refr_1d()

◆ ppath_step_refr_2d()

◆ ppath_step_refr_3d()

◆ ppath_what_background()

◆ resolve_lon()

◆ zaaa2cart()

Variable Documentation

◆ ANGTOL

◆ POLELAT