variogram
The variogram object captures the parameters of variogram models as used in geostatistical analysis and modelling. A variogram describes the degree of spatial dependence of properties such as mineral grades, porosity, or petrophysical properties. It is used to quantify how data points are related to each other based on their spatial separation and direction.
A variogram is required anytime one uses the Kriging family of algorithms, including most geostatistical conditional simulations and non-linear estimation methods such as LUC and MIK.
The variogram model object can be composed of several structures. Each structure is independently composed of a type (e.g., spherical, exponential) and an anisotropy (ranges, sill and rotation angles).
The anisotropy of the variogram is described as an ellipsoid. An ellipsoid is defined by three lengths for the major, semi-major, and minor axes, rotated in space as defined by the rotation and perpendicularlly related. Rotation in 3D is described by three angles—azimuth, dip, and pitch—applied sequentially: first around the Z-axis, then the X-axis, and finally the Z-axis again to determine the plunge direction (major axis). All angles must be positive values in degrees, within the defined bounds for each rotation. In the XY plane, a dip azimuth of 0° points North.
This object also captures additional context of the data underlying the model and can be associated with:
- Modelling space: data (raw) space or normal score space.
- Domain: the name of the domain that is represented by this variogram model.
- Attribute: the name of the data property that was used to model this variogram.
- Declustering: Using or not the declustering weight.
This object can be used when performing kriging, conditional simulations, and change of support analysis. It is typically created from a variogram modeling application.
Properties
variogram (v1.2.0)
Variogram model and associated metadata. The variogram model is defined by the nugget, and multiple structures using the leapfrog-convention rotation. See struture and rotation components for additional details.
| Property | Type | Description | Flags |
|---|---|---|---|
| name | String | Name of the object. | ⬆️ ✅ |
| uuid | base-object-properties | Identifier of the object. | ⬆️ ✅ |
| description | String | Optional field for adding additional description to uniquely identify this object. | ⬆️ |
| extensions | Object | Extended properties that may be associated to the object, but not specified in the schema | ⬆️ |
| tags | Object | Key-value pairs of user-defined metadata | ⬆️ |
| lineage | lineage | Information about the history of the object | ⬆️ |
| schema | String | ✅ | |
| nugget | Number | The variance between two samples separated by near-zero lag distance, representing the randomness present. When plotted, this value is the y-intercept. | |
| sill | Number | The variance of the variogram. This must be within a very small tolerance of the nugget plus the sum of all structure's contributions. | ✅ |
| data_variance | Number | The variance of the data, if different from the sill value, this is used for normalising or rescaling the variogram | |
| is_rotation_fixed | Boolean | Boolean value specifying whether all structure's rotations are the same. | ✅ |
| structures | Array[variogram] | A list of at least one mathematical model, which are parameterised to represent the spatial structure of the variogram model. | ✅ |
| modelling_space | String | The modelling space the variogram model was fitted in either data for original units or normalscore for gaussian space. | |
| domain | String | The domain the variogram is modelled for | |
| attribute | String | The attribute the variogram is modelled for |
Legend
| Flag | Description |
|---|---|
| ⬆️ | Inherited property |
| ✅ | Required property |
