Tipper

This object can be used to store tipper (ZTEM) surveys - a natural-source geophysical method. Data are provided in the frequency-domain as point source measurements of tipper data.

The following example shows how to generate a tipper survey with associated data stored in geoh5 format and accessible from Geoscience ANALYST.

from pathlib import Path

import numpy as np

from geoh5py.objects import TipperBaseStations, TipperReceivers
from geoh5py.workspace import Workspace


# Create a new project
h5file = Path("my_project.geoh5")
workspace = Workspace(h5file) if h5file.exists() else Workspace.create(h5file)

# Define the pole locations
n_stations = 64
n_lines = 2
x_loc, y_loc = np.meshgrid(
    np.linspace(0, 60, n_stations), np.linspace(-20, 20.0, n_lines)
)
vertices = np.c_[x_loc.ravel(), y_loc.ravel(), np.zeros_like(x_loc).ravel()]

# Assign a line ID to the poles (vertices)
parts = np.kron(np.arange(n_lines), np.ones(n_stations)).astype("int")

# Create the survey from vertices
receivers = TipperReceivers.create(workspace, vertices=vertices, parts=parts)
base = TipperBaseStations.create(workspace, vertices=vertices)

We have so far created two seperate entities, one for the receiver locations and another for the base station(s). In order to finalize the survey, the association must be made between the two entities:

receivers.base_station = base

or equivalently

base.receivers = receivers

Only one of the two options above is needed.

Metadata

Along with the geoh5py.objects.surveys.electromagnetics.tipper.TipperReceivers, the metadata contains all the necessary information to define the geophysical experiment.

receivers.metadata

{'EM Dataset': {'Base stations': UUID('2cc67025-c8ab-4a71-a103-c62fa9898488'),
  'Channels': [],
  'Input type': 'Rx and base stations',
  'Property groups': [],
  'Receivers': UUID('f4a32a54-1158-4eb9-8c8e-96e092efe670'),
  'Survey type': 'ZTEM',
  'Unit': 'Hertz (Hz)'}}

Channels

List of frequencies at which the data are provided.

receivers.channels = [30.0, 45.0, 90.0, 180.0, 360.0, 720.0]

Input type

Generic label used in the geoh5 standard for all EM survey entities. Restricted to Rx and base station in the case of a tipper survey.

Property groups

List of geoh5py.groups.property_group.PropertyGroup instances defining the various data components (e.g. Txz (real), Tyz (imag), …). It is not required to supply all components of the impedence tensor, but it is expected that each component contains a list of data channels of length and in the same order as the Channels (one Data per frequency).

The class method geoh5py.objects.surveys.electromagnetics.base.BaseEMSurvey.add_components_data() can help users add data from nested dictionaries. Below is an example using four components:

# Arbitrary data generator using sine functions
def data_fun(c, f):
    return (c + 1.0) * (f + 1.0) * np.sin(f * np.pi * (x_loc * y_loc).ravel() / 400.0)


# Create a nested dictionary of component and frequency data.
data = {
    component: {
        f"{component}_{freq}": {"values": data_fun(cc, ff)}
        for ff, freq in enumerate(receivers.channels)
    }
    for cc, component in enumerate(
        [
            "Txz (real)",
            "Txz (imaginary)",
            "Tyz (real)",
            "Tyz (imaginary)",
        ]
    )
}

receivers.add_components_data(data)

[<geoh5py.groups.property_group.PropertyGroup at 0x777a982b1c10>,
 <geoh5py.groups.property_group.PropertyGroup at 0x777a59c61cd0>,
 <geoh5py.groups.property_group.PropertyGroup at 0x777a59ca1490>,
 <geoh5py.groups.property_group.PropertyGroup at 0x777a59ca3aa0>]

Metadata are updated immediately to reflect the addition of components:

receivers.metadata

{'EM Dataset': {'Base stations': UUID('2cc67025-c8ab-4a71-a103-c62fa9898488'),
  'Channels': [30.0, 45.0, 90.0, 180.0, 360.0, 720.0],
  'Input type': 'Rx and base stations',
  'Property groups': ['Txz (real)',
   'Txz (imaginary)',
   'Tyz (real)',
   'Tyz (imaginary)'],
  'Receivers': UUID('f4a32a54-1158-4eb9-8c8e-96e092efe670'),
  'Survey type': 'ZTEM',
  'Unit': 'Hertz (Hz)'}}

Data channels associated with each component can be quickly accessed through the geoh5py.objects.surveys.electromagnetics.base.BaseEMSurvey.components() property:

receivers.components

{'Txz (real)': [<geoh5py.data.float_data.FloatData at 0x777a5ab98410>,
  <geoh5py.data.float_data.FloatData at 0x777a59f872f0>,
  <geoh5py.data.float_data.FloatData at 0x777a59d68080>,
  <geoh5py.data.float_data.FloatData at 0x777a59df9a60>,
  <geoh5py.data.float_data.FloatData at 0x777aa84767e0>,
  <geoh5py.data.float_data.FloatData at 0x777a98242de0>],
 'Txz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x777aa8140500>,
  <geoh5py.data.float_data.FloatData at 0x777aaaf81cd0>,
  <geoh5py.data.float_data.FloatData at 0x777aa84f91f0>,
  <geoh5py.data.float_data.FloatData at 0x777a59c62a80>,
  <geoh5py.data.float_data.FloatData at 0x777a800a6a50>,
  <geoh5py.data.float_data.FloatData at 0x777a59c61a00>],
 'Tyz (real)': [<geoh5py.data.float_data.FloatData at 0x777aa81402f0>,
  <geoh5py.data.float_data.FloatData at 0x777a59c3a270>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca20c0>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca1fa0>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca1310>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca1580>],
 'Tyz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x777a9820b3e0>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca3470>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca35c0>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca3710>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca3860>,
  <geoh5py.data.float_data.FloatData at 0x777a59ca3980>]}

Receivers

Generic label used in the geoh5 standard for EM survey to identify the geoh5py.objects.surveys.electromagnetics.tipper.TipperReceivers entity.

Base stations

Generic label used in the geoh5 standard for EM survey to identify the geoh5py.objects.surveys.electromagnetics.tipper.TipperBaseStations entity.

Survey type

Label identifier for ZTEM survey type.

Unit

Units for frequency sampling of the data: Hertz (Hz), KiloHertz (kHz), MegaHertz (MHz) or Gigahertz (GHz).

workspace.finalize()