public void TestST3DDistance()
        {
            using (var db = new PostGisTestDataConnection(TestDatabaseConnectionString))
            {
                Assert.AreEqual(
                    1.732,
                    db.Select(() => MeasurementFunctions.ST3DDistance(
                                  "POINT(0 0 0)",
                                  "POINT(1 1 1)")).Value,
                    1.0E-3);

                Assert.IsNull(db.Select(() => MeasurementFunctions.ST3DDistance((NTSG)null, (NTSG)null)));
            }
        }