TheaimofthispaperistogiveupperboundsofthenormoftheoperatorandassociatederrorforaLagrangeinterpolationproblembyC~1quadraticsplines.Thedomainisrectangularandthetype-2triangulationisnon--uniform.Moreoverthelocationofdatapointsallowsaverysimplecompationoftheinterpolant.