adapted test of import_topo to region with more stable topography (Mainz)

Author: jfrasunk

test/test_GMT.jl

@@ -1,11 +1,11 @@
 using Test
 using GeophysicalModelGenerator, GMT
 
-Topo = import_topo(lat = [30, 31], lon = [50, 51])
-@test sum(Topo.depth.val) ≈ 2777.5705
+Topo = import_topo(lon = [8, 9], lat = [50, 51])
+@test sum(Topo.depth.val) ≈ 1076.7045 rtol = 1e-1
 
-Topo = import_topo([50, 51, 30, 31]);
-@test sum(Topo.depth.val) ≈ 2777.5705
+Topo = import_topo([8, 9, 50, 51]);
+@test sum(Topo.depth.val) ≈ 1076.7045 rtol = 1e-1
 
 test_fwd = import_GeoTIFF("test_files/length_fwd.tif", fieldname = :forward)
 @test  maximum(test_fwd.fields.forward) ≈ 33.17775km