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Simone

Geovolumes not closing

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Hi

I am calculating volumes using the Geovolumes tool, i am doing this for several discrete lenses in my area, i am adding a celing and floor raster to make sure the volume i want is enclosed to the top and bottom, however when running the "Is 3D closed?" tool it indicates that the middle layer (being my aquifer) is not closed dispite both the upper and lower layers being closed, is there a way to rectify this without changing the extent of the tin? Basically we are trying to calculate the change in volume of the aquifer over time and therfore the spatial extent of the aquifer is likely to change but i would like to keep the boundary the same for all years to keep the analysis consistent from one year to the next. Any help would be appreciated

Cheers

Simone

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Does the tin have to be the exact extent of saturation, like will it not close if some of the layer does not exist in some places? For example i have a celing layer which is my water level as the bottom and an arbitrary constant value raster as the top (set to higher than any elevation the WL raster reaches) then i have the aquifer volume which is the water level raster and the bottom of the aquifer raster, then underneath i have a floor volume being the bottom of the aquifer rater and an arbitrary constant value raster which exists at a depth below the lowest point observed in the base of the aquifer raster. The celing and floor volumes will always have a volume across the spatial extent of the tin becuse of the thickness set, but becasue i am trying to use the same tin for each year that i do the analysis there are some times when the aquifer volume will not be saturated to the full extent of the tin and therefore in some locations the floor volume abuts the celing volume and the aquifer volume does not exist. Is this why it is not closing? because its not consistent along the whole spatial extent of the tin? If so then am i right in assuming i need to make a seperate tin for each year based on the extent of the aquifer saturation? The reason i am trying to maintain the one tin is becuase i am undertaking this for 18 different small lenses across 1 (of 2) areas for 10 different years, thats creating 180 different tins, and therfore im trying to avoid this. I have specified in my geovolume creations that i want the minimum volume to be 0m so i thought it should be able to close even if there are areas of 0 thickness.

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also i have some lenses which are not continuous across the extent of the tin which return volumes but then there are these few which dont? im totally confused as to whats the criteria behind wether a volume will close or not

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Hi Simone,

See below some suggestions:

Regarding the closed volumes – we have also found that in some cases the features created are not closed which means you cannot calculate their volume. We are still trying to figure this out and are going back and forth with ESRI’s 3D team. We do not have a solution at this point, but I have a few suggestions you can try.

  • The spacing and smoothness of the TIN is a factor – you can try to smooth/simplify the boundary polygon before creating the TIN.
  • Create the TIN with a larger spacing - the denser the points (more detailed TIN) you have more chance to run into issues with the volume.
  • Increase the minimum thickness parameter in the Rasters to GeoVolumes tool.

Using a single TIN for multiple boundaries:

Your approach of using a single TIN for multiple raster boundaries can work however there are some complications here:

  • If you are using a single GeoRasters raster catalog to store the rasters then you need to specify for each run which of the rasters should be used. It won’t make sense to run the Rasters To GeoVolumes tool for all rasters at once as the tool looks for horizon ids and then fills between them.
  • A workaround would be to use the Definition Query to filter the GeoRasters you want to use for each run. I tested this and it works nicely. Using the Definition query on the raster catalog you can specify each time the rasters you want to use and then run the Rasters To GeoVolumes tool only on those rasters. In this manner you are using a single TIN, but the rasters change every run.
  • Should be fairly easy to write a small python script that modifies the Definition Query on the GeoRasters and then runs the Raster To GeoVolumes tool. This way you would be able to create a list of runs and execute them using a script.

Creating multiple TINs:

Another option is to create a TIN for each zone/lens you want to calculate. You can do the following:

  • Batch the Tin to Polygon tool to create a set of TINs. Notice that you will need to have each boundary polygon in a separate feature class as the tool doesn’t work on multiple polygons in a single feature class.
  • Batch the Rasters To GeoVolumes tool to work on the set of TINS created in the previous step.
  • This doesn’t really solve your initial problem as you will still need to edit/filter the raster catalog each time you want to run the tool. Thus, probably the easiest way is to have the single tin and apply the Definition Query as mentioned above.

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