Package pygeodesy :: Module geoids |
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# Module geoids

Geoid models and interpolations.

Classes GeoidG2012B, GeoidKarney and GeoidPGM to interpolate the height of various geoids at `LatLon` locations or separate lat-/longitudes using different interpolation methods and `geoid` model files.

GeoidKarney is a transcoding of Charles Karney's C++ class Geoid to pure Python. The GeoidG2012B and GeoidPGM interpolators both depend on scipy and numpy and require those packages to be installed.

In addition, each geoid interpolator needs `grid knots` (down)loaded from a `geoid` model file, specific to the interpolator, more details below. For each interpolator, there are several interpolation choices, for example linear, cubic, etc.

Typical usage is as follows. First, create an interpolator from a `geoid` model file, containing locations with known heights also referred to as the `grid knots`.

`>>> ginterpolator = GeoidXyz(geoid_file, **options)`

Then, get the interpolated geoid height of one or several `LatLon` location(s) with

`>>> h = ginterpolator(ll)`

or

`>>> h0, h1, h2, ... = ginterpolator(ll0, ll1, ll2, ...)`

or

`>>> hs = ginterpolator(lls) # list, tuple, generator, ...`

For separate lat- and longitudes invoke the `.height` method as

`>>> h = ginterpolator.height(lat, lon)`

or as

`>>> h0, h1, h2, ... = ginterpolator.height(lats, lons) # lists, tuples, ...`

Errors from `scipy` are raised as SciPyErrors. Warnings issued by `scipy` can be thrown as SciPyWarning exceptions, provided Python `warnings` are filtered accordingly, see SciPyWarning.

See Also: Karney's GeographicLib, Geoid height and Installing the Geoid datasets, SciPy interpolation RectBivariateSpline and interp2d and the functions elevations.elevation2 and elevations.geoidHeight2.

Version: 21.10.05

Classes
| _GeoidBase (INTERNAL) Base class for `Geoid...`s.
| GeoidError Geoid interpolator `Geoid...` or interpolation issue.
| GeoidG2012B Geoid height interpolator for GEOID12B Model grids CONUS, Alaska, Hawaii, Guam and Northern Mariana Islands, Puerto Rico and U.S. Virgin Islands and American Samoa based on `SciPy` RectBivariateSpline or interp2d interpolation.
| GeoidHeight5Tuple 5-Tuple `(lat, lon, egm84, egm96, egm2008)` for GeoidHeights.dat tests with the heights for 3 different EGM grids at `degrees90` and `degrees180` degrees (after converting `lon` from original `0 <= EasterLon <= 360`).
| GeoidKarney Geoid height interpolator for Karney's GeographicLib Earth Gravitational Model (EGM) geoid egm*.pgm datasets using bilinear or cubic interpolation and caching in pure Python, transcoded from Karney's C++ class Geoid.
| GeoidPGM Geoid height interpolator for Karney's GeographicLib Earth Gravitational Model (EGM) geoid egm*.pgm datasets but based on `SciPy` RectBivariateSpline or interp2d interpolation.
| PGMError Issue parsing or cropping an `egm*.pgm` geoid dataset.

Functions
egmGeoidHeights(GeoidHeights_dat) Generate geoid egm*.pgm height tests from GeoidHeights.dat Test data for Geoids. |

Variables
| __all__ = `_ALL_LAZY.geoids`

Function Details

### egmGeoidHeights (GeoidHeights_dat) |
Generate geoid egm*.pgm height tests from GeoidHeights.dat Test data for Geoids. Arguments: `GeoidHeights_dat` - The un-gz-ed `GeoidHeights.dat` file (`str` or `file` handle). Returns: For each test, yield a GeoidHeight5Tuple`(lat, lon, egm84, egm96, egm2008)`. Raises: `GeoidError` - Invalid `GeoidHeights_dat`. Note: Function egmGeoidHeights is used to test the geoids GeoidKarney and GeoidPGM, see PyGeodesy module `test/testGeoids.py`.