Merge pull request #31 from observerly/feature/solar/GetHorizontalCoo…

…rdinate

feat: add GetHorizontalCoordinate(datetime time.Time, ...) to coordinates module in @observerly/sidera.

pkg/solar/sun.go

@@ -143,10 +143,32 @@ Sun's position relative to the vernal equinox and calculate the time of sunrise,
 */
 func GetEquatorialCoordinate(datetime time.Time) common.EquatorialCoordinate {
 	// get the solar ecliptic coordinate:
-	ecliptic := GetEclipticCoordinate(datetime)
+	ec := GetEclipticCoordinate(datetime)
 
 	// convert the solar ecliptic coordinate to the solar equatorial coordinate:
-	return coordinates.ConvertEclipticToEquatorialCoordinate(datetime, ecliptic)
+	return coordinates.ConvertEclipticToEquatorialCoordinate(datetime, ec)
+}
+
+/*****************************************************************************************************************/
+
+/*
+the Horizontal Coordinate of the Sun for a given datetime
+
+The Solar Horizontal Coordinate is the position of the Sun in the sky relative to the observer's local horizon.
+
+The Solar Horizontal Coordinate is an important concept in solar astronomy, as it is used to calculate the position
+of the Sun in the sky at any given time. By knowing the Solar Horizontal Coordinate, an observer can determine the
+Sun's position relative to the vernal equinox and calculate the time of sunrise, sunset, and other solar events.
+*/
+func GetHorizontalCoordinate(
+	datetime time.Time,
+	observer common.GeographicCoordinate,
+) common.HorizontalCoordinate {
+	// get the solar equatorial coordinate:
+	eq := GetEquatorialCoordinate(datetime)
+
+	// convert the solar equatorial coordinate to the solar horizontal coordinate:
+	return coordinates.ConvertEquatorialToHorizontalCoordinate(datetime, observer, eq)
 }
 
 /*****************************************************************************************************************/

pkg/solar/sun_test.go

@@ -25,6 +25,14 @@ var datetime time.Time = time.Date(2021, 5, 14, 0, 0, 0, 0, time.UTC)
 
 /*****************************************************************************************************************/
 
+var observer common.GeographicCoordinate = common.GeographicCoordinate{
+	Latitude:  19.8207,
+	Longitude: -155.468094,
+	Elevation: 4205,
+}
+
+/*****************************************************************************************************************/
+
 func TestGetSolarMeanAnomaly(t *testing.T) {
 	var got float64 = GetMeanAnomaly(datetime)
 
@@ -94,3 +102,22 @@ func TestSolarEquatorialCoordinate(t *testing.T) {
 }
 
 /*****************************************************************************************************************/
+
+func TestSolarHorizontalCoordinate(t *testing.T) {
+	var got = GetHorizontalCoordinate(datetime, observer)
+
+	var want = common.HorizontalCoordinate{
+		Azimuth:  271.018685,
+		Altitude: 72.7850383767226,
+	}
+
+	if got.Azimuth-want.Azimuth > 0.0001 {
+		t.Errorf("got %f, wanted %f", got.Azimuth, want.Azimuth)
+	}
+
+	if got.Altitude-want.Altitude > 0.0001 {
+		t.Errorf("got %f, wanted %f", got.Altitude, want.Altitude)
+	}
+}
+
+/*****************************************************************************************************************/