{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Viewshed Analysis"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "This notebook is a basic introduction to viewshed analysis in *GRASS GIS* in *Jupyter Notebook*. In addition to common *Python* packages, it demonstrates the usage of `grass.script`, the *Python* API for GRASS GIS, and `grass.jupyter`, an experimental *Jupyter Notebook* specific package that helps with the launch of *GRASS GIS* and with displaying maps.\n",
    "\n",
    "This interactive notebook is available online thanks to the [https://mybinder.org](Binder) service. To run the select part (called a *cell*), hit `Shift + Enter`."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Starting GRASS in Jupyter Notebooks"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Import Python standard library and IPython packages we need.\n",
    "import os\n",
    "import subprocess\n",
    "import sys\n",
    "\n",
    "# Ask GRASS GIS where its Python packages are.\n",
    "sys.path.append(\n",
    "    subprocess.check_output([\"grass\", \"--config\", \"python_path\"], text=True).strip()\n",
    ")\n",
    "\n",
    "# Import the GRASS GIS packages we need.\n",
    "import grass.script as gs\n",
    "import grass.jupyter as gj\n",
    "\n",
    "# Start GRASS Session\n",
    "session = gj.init(\"../../data/grassdata\", \"nc_basic_spm_grass7\", \"user1\")\n",
    "\n",
    "# Set computational region to elevation raster\n",
    "gs.run_command(\"g.region\", raster=\"elevation@PERMANENT\", flags=\"pg\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Viewshed analysis\n",
    "Compute viewshed from a new 32 story tower located in downtown Raleigh, NC."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "gs.parse_command(\"g.region\", raster=\"elevation\", flags=\"apg\")\n",
    "gs.write_command(\"v.in.ascii\", input=\"-\", stdin=\"%s|%s\" % (642212, 224767), output=\"viewpoints\")\n",
    "gs.run_command(\"r.viewshed\", input=\"elevation\", output=\"tower_los\", coordinates=\"642212,224767\", observer_elevation=\"165\", max_distance=\"10000\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Display result with basemap:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "vs_map = gj.InteractiveMap()\n",
    "\n",
    "vs_map.add_raster(\"tower_los\", opacity=0.7)\n",
    "vs_map.add_vector(\"viewpoints\")\n",
    "vs_map.add_layer_control()\n",
    "\n",
    "vs_map.show()"
   ]
  }
 ],
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