==Неспецифіковані вирівняні поверхні для початку відліку висот==

|-

| ta || Approximate mean sea-level

|-

| tb || Local

| tc || Local LWM

| td || Local MSL

| te || Mean sea-level

| tf || None

| tg || Arbitrary

| th || Mean low water

| ti || Mean low water Springs

|| tj = Mean lower low water

| tk || Mean lower low water Springs

| tl || Lowest normal low water

| tm || Lowest low water

| tn || Indian Spring low water

| to || at or near the level of lowest astronomical tide

| uu || unknown vertical datum

| zz || other known vertical datum

|}