It seems there are many interpretations of what a point depth might be in the context of the whole cave (as compared to just a feature such as a pit). I think Torsten is thinking of an interpretation that I did not think of until his last post. Depth = elevation up or down relative to one of the entrances Depth = elevation down relative to the highest survey station Depth = elevation below (or above if negative) the free water surface Depth = distance below the ground surface directly above the point Depth = others? The first two can be imitated with point altitude as Stacho says, if you don't mind using an arbitrary z origin for your map coordinates. If you adopt the third meaning then the value of a new depth entity could usually be calculated by therion (once modified to include this feature). If you adopt the fourth meaning, then it's value must always be manually entered by the user, as the ground is generally undulating. Mind you, I imagine that therion could perhaps be modified to calculate the depth below ground if a surface grid entity has been entered. Bruce