GMS:Horizons to HUF

The following steps illustrate how to use the Horizons method to create HUF data

1. Create/Import Inputs - There are two main types of inputs for the horizons method:
   1. Boreholes - Boreholes can be created by importing borehole data by using the Text Import Wizard, importing sample data after boreholes already exist, or using the borehole tools to manually enter the boreholes. Once a borehole has been created it can be edited in the Borehole Editor or by using the borehole tools. Also an existing borehole can be copied. Boreholes can be locked to prevent them from being edited.
   2. TINs - TINs can be created 3 different ways in GMS: manually entering the vertex locations and triangulating, converting a different GMS data type to a TIN, and copying a currently existing TIN. (See Creating TINs)
2. Assign Horizon IDs - The term “horizon” refers to the top of each stratigraphic unit that will be represented in a corresponding Solid, HUF unit or Material Layer. Horizons are numbered consecutively in the order that the strata are “deposited” (from the bottom up). Horizons can be assigned to both Boreholes and TINs. (See GMS:Horizons)
3. Create 3D Grid/MODFLOW model - A 3D Grid and MODFLOW model need to be first created to use the Horizon -> HUF command. The flow package for the MODFLOW model must also be set to use the HUF package. Before building a MODFLOW simulation, a 3D grid must be created which covers the area to be modeled. A grid can be created by selecting the Create Grid command in the Grid menu. A suite of tools and commands for editing grids (inserting rows, changing column widths, etc.) are also provided in the 3D Grid Module. If the conceptual model approach is used to construct a MODFLOW model, the grid can be automatically constructed from the conceptual model data using the Grid Frame and the Map -> 3D Grid command in the Feature Objects menu. The grid can be automatically refined around wells and cells outside the model domain can be inactivated.
4. Setup additional optional inputs - Two additional options exist to help constrain and provide user intervention in the Horizon modeling process. The two options are to create borehole cross sections or a horizon conceptual model.
   1. Including Borehole Cross Sections
   2. Horizon Conceptual Model
5. Run the Horizons Wizard - Select the Horizons->3D Mesh command in the Borehole or TIN menu.

Horizon -> HUF Algorithm

File:Samp huf.gif

Example of Horizons to HUF

When the Horizon command is executed the horizons specified on the borehole contacts or TIN nodes are converted to a set of scatter points with one data set for each horizon. The scatter points are then used to interpolate a surface for each horizon. Starting with the lowest numbered horizon, the surface is extruded down to create a HUF layer The surface corresponding to the next horizon is then extruded down to fill in the space between that surface and the previous surface. This process is repeated for each surface. At each step, HUF layer is created for the current horizon and all previously layers are subtracted from that layer, resulting in an incremental buildup of the stratigraphy from the bottom to the top. In conclusion the HUF Package elevation and thickness arrays are generated from the horizon data.