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GC: css2c (#152)
--------- Co-authored-by: Julia Kent <[email protected]>
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‎environment.yml

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@@ -3,6 +3,7 @@ channels:
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- conda-forge
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dependencies:
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# Content
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- astropy
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- cartopy
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- geocat-comp
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- geocat-datafiles

‎ncl/ncl_entries/great_circle.ipynb

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@@ -15,15 +15,16 @@
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"\n",
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"This section covers great circle functions from NCL:\n",
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"\n",
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"- [area_poly_sphere](https://www.ncl.ucar.edu/Document/Functions/Built-in/area_poly_sphere.shtml)"
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"- [area_poly_sphere](https://www.ncl.ucar.edu/Document/Functions/Built-in/area_poly_sphere.shtml)\n",
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"- [css2c](https://www.ncl.ucar.edu/Document/Functions/Built-in/css2c.shtml)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## area_poly_sphere\n",
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"NCL's `area_poly_sphere` calculates the area enclosed by an arbitrary polygon on the sphere\n",
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"NCL's `area_poly_sphere` calculates the area enclosed by an arbitrary polygon on the sphere\n",
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"\n",
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"<div class=\"admonition alert alert-info\">\n",
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" <p class=\"admonition-title\" style=\"font-weight:bold\">Important Note</p>\n",
@@ -58,6 +59,40 @@
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"poly_area_km2"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## css2c\n",
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"NCL's `css2c` converts spherical (latitude/longitude) coordinates to Cartesian coordinates on a unit sphere"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### Grab and Go"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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"from astropy.coordinates.representation import UnitSphericalRepresentation\n",
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"from astropy import units\n",
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"\n",
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"lat = 40.0150\n",
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"lon = -105.2705\n",
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"\n",
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"spherical_coords = UnitSphericalRepresentation(lat=lat * units.deg, lon=lon * units.deg)\n",
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"cart_coords = spherical_coords.to_cartesian()\n",
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"print(f\"X = {cart_coords.x.value}\")\n",
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"print(f\"Y = {cart_coords.y.value}\")\n",
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"print(f\"Z = {cart_coords.z.value}\")"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
@@ -71,6 +106,7 @@
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"source": [
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"## Python Resources\n",
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"- [pyroj.geod() great circle computations](https://pyproj4.github.io/pyproj/stable/api/geod.html)\n",
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"- [Astropy Coordinate Systems](https://docs.astropy.org/en/stable/coordinates/representations.html)\n",
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"\n",
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"## Additional Reading\n",
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"- [Aviation Formulary for working with great circles](https://www.edwilliams.org/avform147.htm)"

‎ncl/ncl_index/ncl-index-table.csv

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@@ -46,4 +46,5 @@ NCL Function,Description,Python Equivalent,Notes
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`daylight_fao56 <https://www.ncl.ucar.edu/Document/Functions/Crop/daylight_fao56.shtml>`__," Compute maximum number of daylight hours as described in FAO 56","``geocat.comp.meteorology.max_daylight()``",`example notebook <../ncl_entries/meteorology.ipynb#daylight-fao56>`__
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`dewtemp_trh <https://www.ncl.ucar.edu/Document/Functions/Built-in/dewtemp_trh.shtml>`__,"Calculates the dew point temperature given temperature and relative humidity","``geocat.comp.dewtemp()``",`example notebook <../ncl_entries/meteorology.ipynb#dewtemp-trh>`__
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`area_poly_sphere <https://www.ncl.ucar.edu/Document/Functions/Built-in/area_poly_sphere.shtml>`__,"Calculates the area enclosed by an arbitrary polygon on the sphere","``pyproj.Geod()`` and ``shapely.geometry.polygon.Polygon()``",`example notebook <../ncl_entries/great_circle.ipynb#area-poly-sphere>`__
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`css2c <https://www.ncl.ucar.edu/Document/Functions/Built-in/css2c.shtml>`__,"Converts spherical coordinates (lat/lon) to Cartesian coordinates on a unit sphere","``astropy.UnitSphericalRepresentation()``",`example notebook <../ncl_entries/great_circle.ipynb#css2c>`__
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`satvpr_temp_fao56 <https://www.ncl.ucar.edu/Document/Functions/Crop/satvpr_temp_fao56.shtml>`__," Compute saturation vapor pressure using temperature as described in FAO 56","``geocat.comp.saturation_vapor_pressure()``",`example notebook <../ncl_entries/meteorology.ipynb#satvpr-temp-fao56>`__

‎ncl/ncl_raw/great_circle.ncl

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@@ -68,3 +68,18 @@ print(gc_clkwise(lat7, lon7))
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; (0) True
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print(area_poly_sphere(lat7, lon7, 6370.997))
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;(0) 9401.705
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; css2c
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; Adapted from https://www.ncl.ucar.edu/Document/Functions/Built-in/css2c.shtml
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; ncl -n css2c.ncl >> css2c_output.txt
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print("Latitude (Degree), Longitude (Degree), Cartesian X, Cartesian Y, Cartesian Z")
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do lat=-90,90
79+
do lon=-180,180
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begin
81+
cart = css2c(lat, lon)
82+
print (lat + "," + lon + "," + cart(0,0) + "," + cart(1,0) + "," + cart(2,0))
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end
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end do
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end do

‎ncl/receipts/great_circle.ipynb

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@@ -24,7 +24,8 @@
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"metadata": {},
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"source": [
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"## Functions covered\n",
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"- [area_poly_sphere](https://www.ncl.ucar.edu/Document/Functions/Built-in/area_poly_sphere.shtml)"
27+
"- [area_poly_sphere](https://www.ncl.ucar.edu/Document/Functions/Built-in/area_poly_sphere.shtml)\n",
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"- [css2c](https://www.ncl.ucar.edu/Document/Functions/Built-in/css2c.shtml)"
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]
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},
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{
@@ -53,10 +54,18 @@
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"## Python Functionality"
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]
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},
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{
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"cell_type": "markdown",
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"id": "6dc1d6c4-ac26-4346-9aa3-2c73182a7511",
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"metadata": {},
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"source": [
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"### area_poly_sphere"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "95225429-62d5-4d38-b170-850526c28107",
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"id": "2ba99b37-a743-4776-bc7b-d5a08b977642",
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"metadata": {},
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"outputs": [],
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"source": [
@@ -73,24 +82,8 @@
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" \"Half of the World\",\n",
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" \"Single Point -> Invalid NCL\",\n",
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" \"Single Degree\",\n",
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"]"
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]
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},
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{
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"cell_type": "markdown",
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"id": "6dc1d6c4-ac26-4346-9aa3-2c73182a7511",
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"metadata": {},
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"source": [
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"### area_poly_sphere"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "2ba99b37-a743-4776-bc7b-d5a08b977642",
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"metadata": {},
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"outputs": [],
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"source": [
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"]\n",
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"\n",
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"ncl_lat = [\n",
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" [40.0150, 42.3601, 29.5518],\n",
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" [41.00488, 41.00203, 37.00540, 37.00051],\n",
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"ncl_results[poly_name[4]] = 54450.39\n",
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"ncl_results[poly_name[5]] = 255032000\n",
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"ncl_results[poly_name[6]] = -127516000\n",
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"ncl_results[poly_name[7]] = 9401.705"
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"ncl_results[poly_name[7]] = 9401.705\n",
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"\n",
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"from pyproj import Geod\n",
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"\n",
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"python_results = {}\n",
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"geod = Geod(ellps=\"sphere\") # radius = 6370997 m\n",
120+
"for i in range(len(poly_name)):\n",
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" poly_area_m, _ = geod.polygon_area_perimeter(ncl_lon[i], ncl_lat[i])\n",
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" poly_area_km2 = abs(poly_area_m) * 1e-6\n",
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" python_results[poly_name[i]] = poly_area_km2"
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]
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},
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{
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"cell_type": "markdown",
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"id": "c0e65c3e-2377-47ec-b94c-e7eb753966d9",
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"metadata": {},
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"source": [
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"### css2c"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "35803c5d-bf83-4a35-b61c-50466d9d5095",
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"id": "35abde81-5843-4504-8e32-a137ee1aa094",
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"metadata": {},
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"outputs": [],
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"source": [
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"from pyproj import Geod\n",
141+
"import geocat.datafiles as gdf\n",
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"import numpy as np\n",
143+
"from astropy.coordinates.representation import UnitSphericalRepresentation\n",
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"from astropy import units\n",
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"\n",
133-
"python_results = {}\n",
134-
"geod = Geod(ellps=\"sphere\") # radius = 6370997 m\n",
135-
"for i in range(len(poly_name)):\n",
136-
" poly_area_m, _ = geod.polygon_area_perimeter(ncl_lon[i], ncl_lat[i])\n",
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" poly_area_km2 = abs(poly_area_m) * 1e-6\n",
138-
" python_results[poly_name[i]] = poly_area_km2"
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"css2c_data = gdf.get('applications_files/ncl_outputs/css2c_output.txt')\n",
147+
"css2c_data = np.loadtxt(css2c_data, delimiter=',', skiprows=6)\n",
148+
"\n",
149+
"lat_lon = tuple(map(tuple, (css2c_data[::, 0:2])))\n",
150+
"cart_values = css2c_data[::, 2:]\n",
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"ncl_css2c = dict(zip(lat_lon, cart_values))"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "ee104ea1-e287-4635-b404-5b06ccfb6949",
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"metadata": {},
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"outputs": [],
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"source": [
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"## Collect Latitude and Longtiude Pairs\n",
162+
"lat_lon = []\n",
163+
"for lat in range(-90, 90 + 1):\n",
164+
" for lon in range(-180, 180 + 1):\n",
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" lat_lon.append((lat, lon))\n",
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"\n",
167+
"## Calculate Cartesian coordinates\n",
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"astropy_css2c = {}\n",
169+
"for i, pair in enumerate(lat_lon):\n",
170+
" lat, lon = pair\n",
171+
" spherical_coords = UnitSphericalRepresentation(\n",
172+
" lat=lat * units.deg, lon=lon * units.deg\n",
173+
" )\n",
174+
" cart_coords = spherical_coords.to_cartesian()\n",
175+
" astropy_css2c[pair] = cart_coords.xyz.value"
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]
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},
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{
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146183
"## Comparison"
147184
]
148185
},
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{
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"cell_type": "markdown",
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"id": "384790de-53f9-45d7-8bc1-fef86df21b57",
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"metadata": {},
190+
"source": [
191+
"### area_poly_sphere"
192+
]
193+
},
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{
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"cell_type": "markdown",
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"id": "cb61d4f0-bd10-4034-bfe8-b0c6e9137ec3",
@@ -180,6 +225,28 @@
180225
" if key != \"Single Point -> Invalid NCL\":\n",
181226
" assert False"
182227
]
228+
},
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{
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"cell_type": "markdown",
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"id": "57251c09-ef8c-438f-b3cf-cf798e7f4028",
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"metadata": {},
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"source": [
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"### css2c"
235+
]
236+
},
237+
{
238+
"cell_type": "code",
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"execution_count": null,
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"id": "d5738d2d-5abe-4ed4-8e90-c42881c2bfb0",
241+
"metadata": {},
242+
"outputs": [],
243+
"source": [
244+
"for key in ncl_css2c.keys():\n",
245+
" if key in astropy_css2c.keys():\n",
246+
" assert abs(ncl_css2c[key][0] - astropy_css2c[key][0]) < 0.000005\n",
247+
" assert abs(ncl_css2c[key][1] - astropy_css2c[key][1]) < 0.000005\n",
248+
" assert abs(ncl_css2c[key][2] - astropy_css2c[key][2]) < 0.000005"
249+
]
183250
}
184251
],
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"metadata": {

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