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Fix UTM discontinuity across zones and hemispheres (#41) #42

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Fix UTM discontinuity across zones and hemispheres (#41) #42

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19 changes: 17 additions & 2 deletions Visualizer/ShapeExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,11 +23,26 @@ public static class ShapeExtensions
private const double EccPrimeSquared = (EccSquared) / (1 - EccSquared);

public static ApplicationDataModel.Shapes.Point ToUtm(this ApplicationDataModel.Shapes.Point point)
{
return ProjectToUtm(point, GetLongOrigin(point.X), point.Y < 0);
}

public static ApplicationDataModel.Shapes.Point ToUtmRelativeToSpatialRecordFirstPoint(
this ApplicationDataModel.Shapes.Point point,
ApplicationDataModel.Shapes.Point firstPoint)
{
return ProjectToUtm(point, GetLongOrigin(firstPoint.X), firstPoint.Y < 0);
}

private static ApplicationDataModel.Shapes.Point ProjectToUtm(
ApplicationDataModel.Shapes.Point point,
double longitudeOriginDegrees,
bool applySouthernHemisphereOffset)
{
var latitudeInRadians = point.Y * ConstDeg2Rad;
var longitudeInRadians = point.X * ConstDeg2Rad;

var longitudeOriginInRadians = GetLongOrigin(point.X) * ConstDeg2Rad;
var longitudeOriginInRadians = longitudeOriginDegrees * ConstDeg2Rad;

var n = A / Math.Sqrt(1 - EccSquared * Math.Sin(latitudeInRadians) * Math.Sin(latitudeInRadians));
var t = Math.Tan(latitudeInRadians) * Math.Tan(latitudeInRadians);
Expand All @@ -48,7 +63,7 @@ public static ApplicationDataModel.Shapes.Point ToUtm(this ApplicationDataModel.
(61 - 58 * t + t * t + 600 * c - 330 * EccPrimeSquared) * a1 * a1 * a1 * a1 *
a1 * a1 / 720));

if (point.Y < 0)
if (applySouthernHemisphereOffset)
{
utmNorthing += 10000000.0;
}
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8 changes: 7 additions & 1 deletion Visualizer/SpatialRecordProcessor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ public void ThemeMap(string workingDataKey)

List<Point> projectedPoints = new List<Point>();
List<double> doubleValues = null;
Point? firstPoint = null;
foreach (SpatialRecord record in _spatialRecords)
{
Point? point = record.Geometry.FirstPoint();
Expand All @@ -66,7 +67,12 @@ public void ThemeMap(string workingDataKey)
continue;
}

projectedPoints.Add(point.ToUtm());
if (firstPoint == null)
{
firstPoint = point;
}

projectedPoints.Add(point.ToUtmRelativeToSpatialRecordFirstPoint(firstPoint));

if (_workingDataDictionary.ContainsKey(workingDataKey))
{
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