ericek111
53c15d4061
Window > Grey Line opens the world with the night on it. The dark area is where the sun is down, and the band along its edge is the twilight from the horizon to six degrees below it, which is the grey line an operator watches for on the low bands. Grayline works out where the sun stands: the subsolar point, the elevation at a place, and the latitude the terminator crosses a meridian at, which is what the map fills the night between. It is the same question SunTimes answers from the other end, and the two are checked against each other in the tests. The coastlines are Natural Earth's 110m coastline, public domain, cut to a tenth of a degree. Our own station is drawn from the grid square, the station being called and the spots on the band from the country file. The map follows the clock. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01RoGtneMQaz4M9w7Kk49AVD
74 lines
2.4 KiB
C#
74 lines
2.4 KiB
C#
using Nonemm.Core;
|
|
|
|
namespace Nonemm.Core.Tests;
|
|
|
|
/// Where the sun stands, checked against what the calendar says it must be.
|
|
public class GraylineTests
|
|
{
|
|
[Fact]
|
|
public void TheSunIsOverTheTropicAtTheSolstice()
|
|
{
|
|
(double latitude, _) = Grayline.SubsolarPoint(new DateTime(2026, 6, 21, 12, 0, 0, DateTimeKind.Utc));
|
|
|
|
Assert.Equal(23.4, latitude, 0.1);
|
|
}
|
|
|
|
[Fact]
|
|
public void TheSunIsOverTheEquatorAtTheEquinox()
|
|
{
|
|
(double latitude, _) = Grayline.SubsolarPoint(new DateTime(2026, 3, 20, 14, 46, 0, DateTimeKind.Utc));
|
|
|
|
Assert.Equal(0, latitude, 0.1);
|
|
}
|
|
|
|
/// At noon UTC the sun is over Greenwich, give or take the quarter of an
|
|
/// hour the equation of time moves it by.
|
|
[Fact]
|
|
public void TheSunIsOverGreenwichAtNoon()
|
|
{
|
|
(_, double longitude) = Grayline.SubsolarPoint(new DateTime(2026, 6, 21, 12, 0, 0, DateTimeKind.Utc));
|
|
|
|
Assert.Equal(0, longitude, 1.0);
|
|
}
|
|
|
|
/// The two ways of asking have to agree: at the moment `SunTimes` says the
|
|
/// sun rises, it is on the horizon.
|
|
[Fact]
|
|
public void SunriseAgreesWithTheSunStandingOnTheHorizon()
|
|
{
|
|
(DateTime rise, DateTime set) =
|
|
SunTimes.For(48.15, 17.11, new DateTime(2026, 8, 31, 0, 0, 0, DateTimeKind.Utc))!.Value;
|
|
|
|
Assert.Equal(Grayline.Horizon, Grayline.Elevation(48.15, 17.11, rise), 0.3);
|
|
Assert.Equal(Grayline.Horizon, Grayline.Elevation(48.15, 17.11, set), 0.3);
|
|
}
|
|
|
|
[Fact]
|
|
public void MiddayIsDaylightAndMidnightIsNot()
|
|
{
|
|
DateTime noon = new(2026, 8, 31, 12, 0, 0, DateTimeKind.Utc);
|
|
|
|
Assert.True(Grayline.IsDaylight(0, 0, noon));
|
|
Assert.False(Grayline.IsDaylight(0, 180, noon));
|
|
}
|
|
|
|
/// The terminator crosses every meridian once between the poles while the
|
|
/// sun is over the equator, and the polar day has no crossing at all.
|
|
[Fact]
|
|
public void TheTerminatorCrossesAMeridianWhereTheSunIsOnTheHorizon()
|
|
{
|
|
DateTime moment = new(2026, 8, 31, 12, 0, 0, DateTimeKind.Utc);
|
|
|
|
double crossing = Grayline.LatitudeAt(30, moment)!.Value;
|
|
|
|
Assert.Equal(Grayline.Horizon, Grayline.Elevation(crossing, 30, moment), 0.3);
|
|
}
|
|
|
|
[Fact]
|
|
public void TheNorthPoleIsLitInJuneAndDarkInDecember()
|
|
{
|
|
Assert.True(Grayline.IsNorthPoleLit(new DateTime(2026, 6, 21, 0, 0, 0, DateTimeKind.Utc)));
|
|
Assert.False(Grayline.IsNorthPoleLit(new DateTime(2026, 12, 21, 0, 0, 0, DateTimeKind.Utc)));
|
|
}
|
|
}
|