From 31ed7598ae1d9680e9aca8ced953e70e9ad2f866 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonny=20Sch=C3=A4fer?= <jonny.schaefer@fau.de>
Date: Fri, 16 Sep 2022 11:42:35 +0200
Subject: [PATCH] Add missing files for sphere
---
projection_sphere.go | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
create mode 100644 projection_sphere.go
diff --git a/projection_sphere.go b/projection_sphere.go
new file mode 100644
index 0000000..ab80c58
--- /dev/null
+++ b/projection_sphere.go
@@ -0,0 +1,36 @@
+package radolan
+
+import (
+ "math"
+)
+
+// values described in [1]
+const (
+ earthRadius = 6370.04 // km
+
+ junctionNorth = 60.0 // N
+ junctionEast = 10.0 // E
+)
+
+func (c *Composite) projectSphere(north, east float64) (x, y float64) {
+ rad := func(deg float64) float64 {
+ return deg * (math.Pi / 180.0)
+ }
+
+ lamda0, phi0 := rad(junctionEast), rad(junctionNorth)
+ lamda, phi := rad(east), rad(north)
+
+ m := (1.0 + math.Sin(phi0)) / (1.0 + math.Sin(phi))
+ x = (earthRadius * m * math.Cos(phi) * math.Sin(lamda-lamda0))
+ y = (earthRadius * m * math.Cos(phi) * math.Cos(lamda-lamda0))
+
+ // offset correction
+ x -= c.offx
+ y -= c.offy
+
+ // scaling
+ x /= c.Rx
+ y /= c.Ry
+
+ return
+}
--
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