HydroGeoSphere/Defining New Zones Using ARCVIEW Files

The following commands can be used to assign porous media and surface flow element zone numbers using files created by ESRI Arcview. Note that Arcview .shp and .dbf files should have the same prefix and be in the same directory. Currently, the following Arcview features are not supported:

1. Attributes with a date format.
2. Files containing anything except polygons.
3. Shape files with, for example, geographical projections or coordinate translations that are stored in .shx and .prj files.

Zones from arcview ASCII grid

1. arcview_file_name Name of the Arcview ASCII grid file.
2. nodata_replace Zone number to assign to cells with no data.
3. nzone_add_arcview A number to be added to zone numbers read from the ASCII grid file.

Chosen elements will be assigned zone numbers from the Arcview ASCII grid file (.asc). Since these files are 2-dimensional, elements with the same x- and y-coordinate will be assigned the same zone number, regardless of their z-coordinate.

In cells where there is no data value, the variable nodata_replace will replace the Arcview default (usually -9999).

The variable nzone_add_arcview can be used to preserve existing zone numbers. For example, if there are zones already defined in the model which are numbered from 1 to 7, and the Arcview file contains zones numbered from 1 to 4, you can set nzone_add_arcview to 7, and zones assigned from the Arcview file would be numbered from 8 to 11.

• • •

Zones from arcview

1. arcview_file_name Prefix of the Arcview shape file.
2. nodata_replace Zone number to assign to an element which is not in any polygon
3. attribute Field name used to assign the zones, which must be written exactly as in the .dbf file (case sensitive).
4. nzone_add_arcview A number to be added to zone numbers read from the ASCII grid file.
5. unproject_file If .TRUE, you must supply input data which is identical to that required for the Project grid instruction described in Section 5.3.10.
6. project_file If .TRUE, you must supply input data which is identical to that required for the Project grid instruction described in Section 5.3.10.

Chosen elements will be assigned zone numbers from the Arcview shape file (.shp). Since these files are 2-dimensional, elements with the same x- and y-coordinate will be assigned the same zone number, regardless of their z-coordinate.

If an element centroid falls within a polygon, it will receive the attribute of that polygon. Since a polygon may have several attributes, the variable attribute can be used to specify which one is to be applied. For example, a shapefile of the geology of a region may contain polygons having the attributes age, type, domain, unit, formation and name. Setting the value of attribute to 'domain' will assign zone numbers based on the domain number. The choice of a different attribute will result in a different pattern of zone numbering. The variable attribute is chosen from the database file (.dbf), which can be opened in a spreadsheet program in order to choose the name.

The variable nzone_add_arcview can be used to preserve existing zone numbers. For example, if there are zones already defined in the model which are numbered from 1 to 7, and the Arcview file contains zones numbered from from 1 to 4, you can set nzone_add_arcview to 7, and zones assigned from the Arcview file would be numbered from 8 to 11.

• • •

Since Arcview shape files created on a Windows platform may not be binary compatible with a UNIX platform, the zone numbers can be written to an ASCII file using the write zones to file instruction and then read on the UNIX platform using the read zones from file instruction (as described in Section 5.8.1.2. This can also be useful in cases where the zones from arcview instruction takes a long time to execute, since the results can be stored initially and then read much more quickly in subsequent runs.