Handle coordinates that are outside the grid bounds (#15)

* Handle coordinates that are outside the grid bounds

* Finalize the implementation

* Add tests

* Add more tests

src/grids.jl

@@ -24,16 +24,28 @@ function interpolatelatlon(Datumₛ, Datumₜ, lat, lon)
 end
 
 function _interpolatelatlon(interps::AbstractVector, lat, lon)
-  @inbounds for interp in interps
-    (lonmin, lonmax), (latmin, latmax) = bounds(interp)
-    if lonmin < lon < lonmax && latmin < lat < latmax
-      return interp(lon, lat)
+  itp = zero(eltype(first(interps)))
+  for interp in interps
+    if _inbounds(interp, lat, lon)
+      itp = @inbounds interp(lon, lat)
+      break
     end
   end
-  throw(ArgumentError("coordinates outside of the transform domain"))
+  itp
 end
 
-_interpolatelatlon(interp, lat, lon) = interp(lon, lat)
+function _interpolatelatlon(interp, lat, lon)
+  if _inbounds(interp, lat, lon)
+    @inbounds interp(lon, lat)
+  else
+    zero(eltype(interp))
+  end
+end
+
+function _inbounds(interp, lat, lon)
+  (lonmin, lonmax), (latmin, latmax) = bounds(interp)
+  lonmin < lon < lonmax && latmin < lat < latmax
+end
 
 """
     interpolators(Datumₛ, Datumₜ)

test/converions.jl

@@ -263,7 +263,29 @@
   c3 = convert(LatLon{NTF}, c2)
   @test allapprox(c3, c1)
 
-  # error: coordinates outside of the transform domain
+  # coordinates outside the grid bounds
+  # hgridshift
+  c1 = LatLon{SAD96}(T(10), T(-10))
+  c2 = convert(LatLon{SIRGAS2000}, c1)
+  @test c2.lat ≈ c1.lat
+  @test c2.lon ≈ c1.lon
+
   c1 = LatLon{RD83}(T(65), T(25))
-  @test_throws ArgumentError convert(LatLon{ETRFLatest}, c1)
+  c2 = convert(LatLon{ETRFLatest}, c1)
+  @test c2.lat ≈ c1.lat
+  @test c2.lon ≈ c1.lon
+
+  # pointmotion
+  c1 = LatLonAlt{NAD83CSRS{3}}(T(90), T(10), T(1))
+  c2 = convert(LatLonAlt{NAD83CSRS{4}}, c1)
+  @test c2.lat ≈ c1.lat
+  @test c2.lon ≈ c1.lon
+  @test c2.alt ≈ c1.alt
+
+  # geocgridtranslation
+  c1 = convert(Cartesian, LatLon{NTF}(T(65), T(25)))
+  c2 = convert(Cartesian{RGF93v1}, c1)
+  @test c2.x ≈ c1.x
+  @test c2.y ≈ c1.y
+  @test c2.z ≈ c1.z
 end