I recently acquired ArcGIS Online, and I have been plying with it for a couple days now. I have experience using the desktop version with the spacial analyst extension to create depth to groundwater contour lines, as well as containment concentration isocontours through interpolation. From what I can tell, there is no way to make these kind of maps in the online version? There is an interpolation tool, however it only assesses density and is not (in my opinion) accurate.
Is the only way to make accurate contour maps on the desktop version of ArcMap? I really want to like the online version, however if it can't perform this basic of a task, I'm not sure it's worth it.
The online version isn't a duplicate of the desktop version. They have different purposes. For your type of work, desktop, whether if be ArcMap or ArcGIS Pro would be preferable