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Adding Surface Information returning null values

Question asked by kevinbruce on Jul 27, 2020

Hi everyone, 


I am trying to add 3D surface information to a collection of polygons traced onto an orthophotomosaic of a coral reef, with each polygon comprising an individual coral. By only uploading an orthophotomosaic of the reef and a digital elevation model that I plan to use to add the 3d information for each coral. As such, there is no coordinate system set, but in the past this hasn't been an issue for this work.


What I'm running into is that when I add surface information (3D analyst tool --> Add surface Information), some of the polygons return NULL values for 3D surface area and the 3 slope and Z values. I initially thought it was due to the polygons being too small for the DEM resolution (cell size currently is set at 1cm), however after closer inspection with multiple plots, that isn't always the case. For example: sometimes having a shape area 0.00025 returns nulls, yet 0.0003 will return actual values for the 3D metrics I'm looking for. I've attached a picture showing the table results. 


Has anyone ever ran into this issue before and/or have some suggestions for potential fixes? I'm not extremely literate in ArcMap/GIS, but this message board has proved very helpful in the past so I'm hoping for some more success here!


Thanks for your time,