Detect unit of composite data

catalog.go

@@ -28,3 +28,86 @@ var catalog = map[string]spec{
 	"PY": {200, 224, 200, 200, 1, 1},  // accumulated rainfall
 	"PZ": {200, 2400, 200, 200, 2, 2}, // 3D reflectivity CAPPI
 }
+
+type Unit int
+
+const (
+	Unit_unknown = iota
+	Unit_mm      // mm/interval
+	Unit_dBZ     // dBZ
+	Unit_km      // km
+	Unit_mps     // m/s
+)
+
+func (u Unit) String() string {
+	return []string{"unknown unit", "mm", "dBZ", "km", "m/s"}[u]
+}
+
+var unitCatalog = map[string]Unit{
+	"CH": Unit_mm,
+	"CX": Unit_dBZ,
+	"D2": Unit_mm,
+	"D3": Unit_mm,
+	"EA": Unit_dBZ,
+	"EB": Unit_mm,
+	"EC": Unit_mm,
+	"EH": Unit_mm,
+	"EM": Unit_mm,
+	"EW": Unit_mm,
+	"EX": Unit_dBZ,
+	"EY": Unit_mm,
+	"EZ": Unit_mm,
+	"FX": Unit_dBZ,
+	"FZ": Unit_dBZ,
+	"HX": Unit_dBZ,
+	"OL": Unit_dBZ,
+	"OX": Unit_dBZ,
+	"PA": Unit_dBZ,
+	"PC": Unit_dBZ,
+	"PD": Unit_mps,
+	"PE": Unit_km,
+	"PF": Unit_dBZ,
+	"PG": Unit_dBZ,
+	"PH": Unit_mm,
+	"PI": Unit_dBZ,
+	"PK": Unit_dBZ,
+	"PL": Unit_dBZ,
+	"PM": Unit_dBZ,
+	"PN": Unit_dBZ,
+	"PR": Unit_mps,
+	"PU": Unit_mps,
+	"PV": Unit_mps,
+	"PX": Unit_dBZ,
+	"PY": Unit_mm,
+	"PZ": Unit_dBZ,
+	"RA": Unit_mm,
+	"RB": Unit_mm,
+	"RE": Unit_mm,
+	"RH": Unit_mm,
+	"RK": Unit_mm,
+	"RL": Unit_mm,
+	"RM": Unit_mm,
+	"RN": Unit_mm,
+	"RQ": Unit_mm,
+	"RR": Unit_mm,
+	"RU": Unit_mm,
+	"RW": Unit_mm,
+	"RX": Unit_dBZ,
+	"RY": Unit_mm,
+	"RZ": Unit_mm,
+	"S2": Unit_mm,
+	"S3": Unit_mm,
+	"SF": Unit_mm,
+	"SH": Unit_mm,
+	"SQ": Unit_mm,
+	"TB": Unit_mm,
+	"TH": Unit_mm,
+	"TW": Unit_mm,
+	"TX": Unit_dBZ,
+	"TZ": Unit_mm,
+	"W1": Unit_mm,
+	"W2": Unit_mm,
+	"W3": Unit_mm,
+	"W4": Unit_mm,
+	"WX": Unit_dBZ,
+}

header.go

@@ -52,6 +52,12 @@ func (c *Composite) parseHeader(reader *bufio.Reader) error {
 	// Parse Product - Example: "PG" or "FZ"
 	c.Product = header[:2]
 
+	// Lookup Unit
+	c.DataUnit = Unit_unknown
+	if unit, ok := unitCatalog[c.Product]; ok {
+		c.DataUnit = unit
+	}
+
 	// Parse DataLength - Example: "BY 405160"
 	if _, err := fmt.Sscanf(section["BY"], "%d", &c.dataLength); err != nil {
 		return newError("parseHeader", "could not parse data length: "+err.Error())

radolan.go

@@ -41,6 +41,7 @@ import (
 // which the voxel at position (x, y, z) is accessible by c.DataZ[ z ][ y ][ x ].
 //
 // The rvp-6 value is used differently depending on the product type:
+// (also consult the DataUnit field of the Composite)
 //
 //	Product label            | rvp-6 value represents   | unit
 //	-------------------------+--------------------------+------------------------
@@ -75,6 +76,7 @@ type Composite struct {
 	PlainData [][]RVP6 // rvp-6 data for parsed plain data element [y][x]
 	Px        int      // plain data width
 	Py        int      // plain data height
+	DataUnit Unit
 
 	DataZ [][][]RVP6 // rvp-6 data for each voxel [z][y][x] (composites use only one z-layer)
 	Data  [][]RVP6   // rvp-6 data for each pixel [y][x] at layer 0 (alias for DataZ[0][x][y])