public void ProjectionKauai()
{
var definition = SatelliteRegistry.Locate(Goes17DefinitionPrefix);
Assert.NotNull(definition, "Unable to find satellite definition");
var imageOffset = Constants.Satellite.Offset.TwoKm;
const int x = 1614;
const int y = 1564;
// Convert from scanning angle to geodetic
var scanningX = imageOffset.ToHorizontalScanningAngle(x);
var scanningY = imageOffset.ToVerticalScanningAngle(y);
ReverseGeostationaryProjection.ToLatitudeLongitude(scanningX, scanningY, definition.Longitude, definition.Height, out var latitude, out var longitude);
FromRadians(latitude).Degrees.Should().BeApproximately(21.869911403254573, Precision);
FromRadians(longitude).Degrees.Should().BeApproximately(-159.66206692006023, Precision);
// Convert back to scanning angle
GeostationaryProjection.ToScanningAngle(latitude, longitude, definition, out var scanningXResult, out var scanningYResult);
scanningXResult.Should().BeApproximately(scanningX, Precision);
scanningYResult.Should().BeApproximately(scanningY, Precision);
imageOffset.ToImageCoordinates(scanningXResult, scanningYResult, out var targetX, out var targetY);
Math.Round(targetX).Should().BeApproximately(x, PixelPrecision);
Math.Round(targetY).Should().BeApproximately(y, PixelPrecision);
}
public void ProjectionLakeTaupo()
{
var definition = SatelliteRegistry.Locate(Goes17DefinitionPrefix);
Assert.NotNull(definition, "Unable to find satellite definition");
var imageOffset = Constants.Satellite.Offset.TwoKm;
const int x = 1050;
const int y = 4533;
// Convert from scanning angle to geodetic
var scanningX = imageOffset.ToHorizontalScanningAngle(x);
var scanningY = imageOffset.ToVerticalScanningAngle(y);
ReverseGeostationaryProjection.ToLatitudeLongitude(scanningX, scanningY, definition.Longitude, definition.Height, out var latitude, out var longitude);
FromRadians(latitude).Degrees.Should().BeApproximately(-38.70625734950147, Precision);
FromRadians(longitude).Degrees.Should().BeApproximately(175.9626023681634, Precision);
// Convert back to scanning angle
GeostationaryProjection.ToScanningAngle(latitude, longitude, definition, out var scanningXResult, out var scanningYResult);
scanningXResult.Should().BeApproximately(scanningX, Precision);
scanningYResult.Should().BeApproximately(scanningY, Precision);
imageOffset.ToImageCoordinates(scanningXResult, scanningYResult, out var targetX, out var targetY);
Math.Round(targetX).Should().BeApproximately(x, PixelPrecision);
Math.Round(targetY).Should().BeApproximately(y, PixelPrecision);
}
public void ProjectionCalifornia()
{
var definition = SatelliteRegistry.Locate(Goes17DefinitionPrefix);
Assert.NotNull(definition, "Unable to find satellite definition");
var imageOffset = Constants.Satellite.Offset.TwoKm;
const int x = 3717;
const int y = 1275;
// Convert from scanning angle to geodetic
var scanningX = imageOffset.ToHorizontalScanningAngle(x);
var scanningY = imageOffset.ToVerticalScanningAngle(y);
ReverseGeostationaryProjection.ToLatitudeLongitude(scanningX, scanningY, definition.Longitude, definition.Height, out var latitude, out var longitude);
FromRadians(latitude).Degrees.Should().BeApproximately(28.007393788242464, Precision);
FromRadians(longitude).Degrees.Should().BeApproximately(-115.44783176403854, Precision);
// Convert back to scanning angle
GeostationaryProjection.ToScanningAngle(latitude, longitude, definition, out var scanningXResult, out var scanningYResult);
scanningXResult.Should().BeApproximately(scanningX, Precision);
scanningYResult.Should().BeApproximately(scanningY, Precision);
imageOffset.ToImageCoordinates(scanningXResult, scanningYResult, out var targetX, out var targetY);
Math.Round(targetX).Should().BeApproximately(x, PixelPrecision);
Math.Round(targetY).Should().BeApproximately(y, PixelPrecision);
}
/// <summary>
/// Performs latitude calculations as part of lat/long to scanning angle. These are cached in order to avoid
/// repeating latitude calculations for every pixel.
/// </summary>
private LatitudeCalculations CalculateGeostationaryLatitude(int y)
{
var target = _target;
var yOffset = _yOffset;
return(LatitudeCalculationCache.GetOrAdd(y, angle =>
{
// Convert pixel row to latitude
var projectionY = ProjectionAngleConverter.FromY(y, target.Height + yOffset * 2);
// Perform and cache intermediary geostationary latitude calculations
return GeostationaryProjection.LatitudeCalculations(projectionY);
}));
}
public void TextbookToScanningAngle()
{
var(definition, _) = SatelliteRegistry.Locate(Goes16DefinitionPrefix);
Assert.NotNull(definition, "Unable to find satellite definition");
GeostationaryProjection.ToScanningAngle(
FromDegrees(33.846162).Radians,
FromDegrees(-84.690932).Radians,
definition !,
out var scanningX,
out var scanningY);
scanningX.Should().BeApproximately(-0.023807, Precision);
scanningY.Should().BeApproximately(0.0953439, Precision);
}
public void Invoke(int y)
{
var span = _target.GetPixelRowSpan(y);
// Calculate or retrieve the latitude calculation component of geostationary projection
var latitudeCalculations = CalculateGeostationaryLatitude(y + _yOffset);
// Convert image x,y to Mercator projection angle
var targetWidth = _registration.Width * 2;
var projectionY = ProjectionAngleConverter.FromY(y + _yOffset, _registration.Height);
for (var x = 0; x < span.Length; x++)
{
var projectionX = ProjectionAngleConverter.FromX(x + _xOffset, targetWidth);
// Convert latitude/longitude to geostationary scanning angle
GeostationaryProjection.ToScanningAngle(latitudeCalculations, projectionX, _registration.Definition, out var scanningX, out var scanningY);
// Map pixel from satellite image back to target image
span[x] = GetTargetColour(scanningX, scanningY, projectionY, projectionX);
}
}
