fix index bounds

README.md

@@ -1,8 +1,12 @@
-# wgs84 v2 WIP
 
-```sh
-go get github.com/wroge/wgs84/v2
+<img align="right" src="./logo.png" width="200"/>
+
+## WGS84 - Coordinate Transformations
+
 ```
+github.com/wroge/wgs84/v2
+```  
+
 
 I am currently in the process of rewriting the package. Some things will change and some new features will be added. One of these features is the support of NTv2 grid transformations and other projections, such as Krovak. If you would like to help or have any comments, please report them in the issues.
 

epsg.go

@@ -67,8 +67,8 @@ func EPSG(code int) CRS {
 		crs = Geographic(Helmert(-87, -98, -121, 0, 0, 0, 0), NewSpheroid(6378388, 297))
 	case 4258:
 		crs = Geographic(EPSG(4978), NewSpheroid(6378137, 298.257222101))
-	case 4267:
-		crs = loadNTv2("NTv2_0.gsb", NewSpheroid(6378206.4, 294.978698213898), EPSG(4326))
+	// case 4267:
+	// 	crs = loadNTv2("NTv2_0.gsb", NewSpheroid(6378206.4, 294.978698213898), EPSG(4326))
 	case 4269:
 		crs = Geographic(EPSG(4978), NewSpheroid(6378137, 298.257222101))
 	case 4277:
@@ -123,6 +123,8 @@ func EPSG(code int) CRS {
 		crs = TransverseMercator(EPSG(4312), 16.33333333333333, 0, 1, 750000, 0)
 	case 31287:
 		crs = LambertConformalConic2SP(EPSG(4312), 13.33333333333333, 47.5, 49, 46, 400000, 400000)
+	// case 32024:
+	// 	crs = LambertConformalConic2SP(EPSG(4267), -98, 35, 35.5666666666667, 36.7666666666667, 2000000, 0)
 	case 102109:
 		crs = TransverseMercator(EPSG(4258), 15, 0, 0.9999, 500000, -5000000)
 	case 102157:

wgs84.go

@@ -25,10 +25,6 @@ func Transform(from, to CRS) Func {
 			break
 		}
 
-		if from == to {
-			return chainFunc(toBase...)
-		}
-
 		toBase = append(toBase, from.ToBase)
 
 		from = from.Base()
@@ -114,11 +110,11 @@ func (errorCRS) Spheroid() Spheroid {
 }
 
 func (errorCRS) ToBase(x0, y0, z0 float64) (float64, float64, float64) {
-	return x0, y0, z0
+	return math.NaN(), math.NaN(), math.NaN()
 }
 
 func (errorCRS) FromBase(x0, y0, z0 float64) (float64, float64, float64) {
-	return x0, y0, z0
+	return math.NaN(), math.NaN(), math.NaN()
 }
 
 type Spheroid struct {
@@ -411,8 +407,8 @@ func (n ntv2) Shift(lon, lat float64) (float64, float64) {
 
 	ppr := math.Floor((n.wLong-n.eLong)/n.longInc+0.5) + 1
 	ppc := math.Floor((n.nLat-n.sLat)/n.latInc+0.5) + 1
-	se := row*ppr + col
 
+	se := row*ppr + col
 	sw := se + 1
 	ne := se + ppr
 	nw := ne + 1
@@ -434,10 +430,15 @@ func (n ntv2) Shift(lon, lat float64) (float64, float64) {
 		sw = nw
 	}
 
-	sse := n.values[int(se)]
-	ssw := n.values[int(sw)]
-	sne := n.values[int(ne)]
-	snw := n.values[int(nw)]
+	se_index := min(max(int(se), 0), len(n.values)-1)
+	sw_index := min(max(int(sw), 0), len(n.values)-1)
+	ne_index := min(max(int(ne), 0), len(n.values)-1)
+	nw_index := min(max(int(nw), 0), len(n.values)-1)
+
+	sse := n.values[se_index]
+	ssw := n.values[sw_index]
+	sne := n.values[ne_index]
+	snw := n.values[nw_index]
 
 	dx := fcol - col
 	dy := frow - row