{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "0",
   "metadata": {},
   "source": [
    "# Magnetotellurics\n",
    "\n",
    "This object can be used to store magnetotelluric (MT) surveys - a natural-source geophysical method. Data are provided in the frequency-domain as point source measurements of either impedances or apparent resistity/phase.\n",
    "\n",
    "The following example shows how to generate an MT survey with associated data stored in `geoh5` format and accessible from [Geoscience ANALYST](https://mirageoscience.com/mining-industry-software/geoscience-analyst/).\n",
    "\n",
    "\n",
    "![mtSurvey](./images/mt_survey.png)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "1",
   "metadata": {},
   "outputs": [],
   "source": [
    "import numpy as np\n",
    "from geoh5py.workspace import Workspace\n",
    "from geoh5py.objects import MTReceivers\n",
    "\n",
    "# Create a new project\n",
    "workspace = Workspace(\"my_project.geoh5\")\n",
    "\n",
    "# Define a synthetic survey with receivers on 2 lines, 60 m apart\n",
    "x_loc, y_loc = np.meshgrid(np.linspace(-5, 5, 2), np.linspace(0., 20., 9))\n",
    "vertices = np.c_[x_loc.ravel(), y_loc.ravel(), np.zeros_like(x_loc).ravel()]\n",
    "\n",
    "# Create the survey from vertices\n",
    "mt_survey = MTReceivers.create(workspace, vertices=vertices)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2",
   "metadata": {},
   "source": [
    "Only receivers are needed to define the survey as MT uses the ambient electromagntic field of the Earth - no transmitters (source) required."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "3",
   "metadata": {},
   "source": [
    "## Metadata\n",
    "\n",
    "Along with the [MTReceivers](../api/geoh5py.objects.surveys.electromagnetics.rst#module-geoh5py.objects.surveys.electromagnetics.magnetotellurics), the metadata contains all the necessary information to define the geophysical experiment."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "4",
   "metadata": {},
   "outputs": [],
   "source": [
    "mt_survey.metadata"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5",
   "metadata": {},
   "source": [
    "### Channels\n",
    "\n",
    "List of frequencies at which the data are provided."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "6",
   "metadata": {},
   "outputs": [],
   "source": [
    "mt_survey.channels = [1., 10., 100.]"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7",
   "metadata": {},
   "source": [
    "### Input type\n",
    "\n",
    "Generic label used in the `geoh5` standard for all EM survey entities. Restricted to `Rx only` in the case of natural sources methods."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8",
   "metadata": {},
   "source": [
    "### Property groups\n",
    "\n",
    "List of [PropertyGroup](../api/geoh5py.groups.rst#module-geoh5py.groups.property_group)s defining the various data components (e.g. `Zxx (real)`, `Zxy (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).\n",
    "\n",
    "The class method [add_components_data](../api/geoh5py.objects.surveys.electromagnetics.rst#geoh5py.objects.surveys.electromagnetics.base.BaseEMSurvey.add_components_data) can help users add data from nested dictionaries. Below is an example using four components:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "9",
   "metadata": {},
   "outputs": [],
   "source": [
    "# Arbitrary data generator using sine functions\n",
    "data_fun = lambda c, f: (c+1.) * np.sin(f * np.pi * (x_loc * y_loc).ravel() / 200.)\n",
    "\n",
    "# Create a nested dictionary of component and frequency data.\n",
    "data = {\n",
    "    component : {\n",
    "        f\"{component}_{freq}\": {\"values\": (ff+1)*1000. + (cc+1) * 100. + np.arange(vertices.shape[0])} for ff, freq in enumerate(mt_survey.channels)\n",
    "    } for cc, component in enumerate([\n",
    "        \"Zxx (real)\", \"Zxx (imaginary)\",\n",
    "        \"Zxy (real)\", \"Zxy (imaginary)\",\n",
    "        \"Zyx (real)\", \"Zyx (imaginary)\",\n",
    "        \"Zyy (real)\", \"Zyy (imaginary)\",\n",
    "    ])\n",
    "}\n",
    "    \n",
    "mt_survey.add_components_data(data)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "10",
   "metadata": {},
   "source": [
    "Metadata are updated immediately to reflect the addition of components:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "11",
   "metadata": {},
   "outputs": [],
   "source": [
    "mt_survey.metadata"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "12",
   "metadata": {},
   "source": [
    "Data channels associated with each component can be quickly accessed through the [BaseEMSurvey.components](../api/geoh5py.objects.surveys.electromagnetics.rst#geoh5py.objects.surveys.electromagnetics.base.BaseEMSurvey.components) property:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "13",
   "metadata": {},
   "outputs": [],
   "source": [
    "mt_survey.components"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "14",
   "metadata": {},
   "source": [
    "### Receivers\n",
    "\n",
    "Generic label used in the `geoh5` standard for EM survey to identify the receiver entity. Restricted to itself in the case of `MTReceivers`."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "15",
   "metadata": {},
   "source": [
    "### Survey type\n",
    "\n",
    "Label identifier for `Magnetotellurics` survey type."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "16",
   "metadata": {},
   "source": [
    "### Unit\n",
    "\n",
    "Units for frequency sampling of the data: `Hertz (Hz)`, `KiloHertz (kHz)`, `MegaHertz (MHz)` or `Gigahertz (GHz)`."
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3 (ipykernel)",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.9.7"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}