GXTC class

class GXTC(handle=0)

GXTC class.

The GXTC object is used in gravitational modelling to create a terrain correction grid from a topography grid. This is accomplished with a call first to grregter, which determines the terrain correction from an input topography grid, then to grterain, which calculates the actual corrections at the input positions.

classmethod create(img, elev_unit, dinner, douter, dens_t, dens_w, elev_w, edge, edge_elev, opt)

Creates a Terrain Correction object

Parameters:
  • img (GXIMG) – Topo (DEM) grid
  • elev_unit (float) – Elevation unit in 1 metre (i.e. 0.3048 for feet)
  • dinner (float) – Inner distance (in topo grid projection units, default in metres)
  • douter (float) – Outer distance (in topo grid projection units, default in metres)
  • dens_t (float) – Terrain density in g/cc
  • dens_w (float) – Water density in g/cc
  • elev_w (float) – Water reference elevation (in elevation unit)
  • edge (int) – 1 to calculate an edge correction (compensation), 0 otherwise
  • edge_elev (float) – Average elevation beyond max distance (in elevation unit)
  • opt (int) – TC_OPT constants
Returns:

GXTC Object
Return type:

GXTC

New in version 5.0.

License: Geosoft Extended End-User License

classmethod create_ex(img, elev_unit, dinner, douter, dens_t, dens_w, elev_w, edge, edge_elev, opt, survey_type)

Creates a Terrain Correction object with surveytype

Parameters:
  • img (GXIMG) – Topo (DEM) grid
  • elev_unit (float) – Elevation unit in 1 metre (i.e. 0.3048 for feet)
  • dinner (float) – Inner distance (in topo grid projection units, default in metres)
  • douter (float) – Outer distance (in topo grid projection units, default in metres)
  • dens_t (float) – Terrain density in g/cc
  • dens_w (float) – Water density in g/cc
  • elev_w (float) – Water reference elevation (in elevation unit)
  • edge (int) – 1 to calculate an edge correction (compensation), 0 otherwise
  • edge_elev (float) – Average elevation beyond max distance (in elevation unit)
  • opt (int) – TC_OPT constants
  • survey_type (int) – TC_SURVEYTYPE constants
Returns:

GXTC Object
Return type:

GXTC

New in version 6.2.

License: Geosoft Extended End-User License

g_gterain(gv_vx, p3, p4, p5, p6, p7, p8)

Calculate GG terrain corrections

Parameters:
  • gv_vx (GXVV) – Input X channel data (in topo grid projection units, default in metres)
  • p3 (GXVV) – Input Y channel data (in topo grid projection units, default in metres)
  • p4 (GXVV) – Input Elevation channel data (in elevation unit)
  • p5 (GXVV) – Output Terrain Corrected channel data
  • p6 (float) – Terrain density (default 2.67)
  • p7 (float) – Terrain reference level (default 0.0)
  • p8 (int) – GG_ELEMENT constants

New in version 6.0.

License: Geosoft Extended End-User License

grregter(im_gi, im_go)

Create a terrain correction grid for a topo grid.

Parameters:
  • im_gi (GXIMG) – Input GXIMG (local DEM topo grid used for station elevation)
  • im_go (GXIMG) – Image of output grid

New in version 5.0.

License: Geosoft Extended End-User License

grterain(gv_vx, gv_vy, gv_velev, gv_vslop, gv_vtcor, im_gcor, dens_t)

Calculate terrain corrections.

Parameters:
  • gv_vx (GXVV) – Input X channel data (in topo grid projection units, default in metres)
  • gv_vy (GXVV) – Input Y channel data (in topo grid projection units, default in metres)
  • gv_velev (GXVV) – Input Elevation channel data (in elevation unit)
  • gv_vslop (GXVV) – Input slope channel data
  • gv_vtcor (GXVV) – Output Terrain Corrected channel data
  • im_gcor (GXIMG) – Image of input correction grid
  • dens_t (float) – Terrain density (default 2.67)

New in version 5.0.

License: Geosoft Extended End-User License

grterain2(gv_vx, gv_vy, gv_velev, gv_vslop, gv_vwater, gv_vtcor, im_gcor, dens_t)

Calculate terrain corrections (work for marine gravity too).

Parameters:
  • gv_vx (GXVV) – Input X channel data (in topo grid projection units, default in metres)
  • gv_vy (GXVV) – Input Y channel data (in topo grid projection units, default in metres)
  • gv_velev (GXVV) – Input Elevation channel data (in elevation unit)
  • gv_vslop (GXVV) – Input slope channel data
  • gv_vwater (GXVV) – Input Water depth channel data (in metres)
  • gv_vtcor (GXVV) – Output Terrain Corrected channel data
  • im_gcor (GXIMG) – Image of input correction grid
  • dens_t (float) – Terrain density (default 2.67)

New in version 6.0.

License: Geosoft Extended End-User License

is_null()

Check if this is a null (undefined) instance

Returns:True if this is a null (undefined) instance, False otherwise.
Return type:bool
classmethod null()

A null (undefined) instance of GXTC

Returns:A null GXTC
Return type:GXTC

TC_OPT constants

Optimization

TC_OPT_NONE

(slow) no optimization

gxapi.TC_OPT_NONE = 0
TC_OPT_MAX

(faster) desampling and using qspline (4x4 points) interpolation on coarser averaged grid

gxapi.TC_OPT_MAX = 1

TC_SURVEYTYPE constants

Survey Type

TC_SURVEYTYPE_GROUND

Ground

gxapi.TC_SURVEYTYPE_GROUND = 0
TC_SURVEYTYPE_SHIPBORNE

Shipborne

gxapi.TC_SURVEYTYPE_SHIPBORNE = 1
TC_SURVEYTYPE_AIRBORNE

Airborne

gxapi.TC_SURVEYTYPE_AIRBORNE = 2

GG_ELEMENT constants

GG element

GG_ELEMENT_XX

Gxx

gxapi.GG_ELEMENT_XX = 0
GG_ELEMENT_YY

Gyy

gxapi.GG_ELEMENT_YY = 1
GG_ELEMENT_XY

Gxy

gxapi.GG_ELEMENT_XY = 2
GG_ELEMENT_XZ

Gxz

gxapi.GG_ELEMENT_XZ = 3
GG_ELEMENT_YZ

Gyz

gxapi.GG_ELEMENT_YZ = 4