1. Velgrid interpolation dialog

The method for using this dialog is schematically represented in Diagram B - Use of Velgrid.

Figure 1.  Velocity interpolation dialog.

1A - Bathymetry file from Hydrodynamic Model (HM)

This feature is used to generate files containing bathymetry information. It does not interpolate bathymetry data, it creates a file containing the longitude, latitude and depth of each grid node on the uninterpolated grid.  It is not essential to use this feature. For details on using this section, see 2A - Use this feature and specify bathymetry.


Grid size and position information for uninterpolated data from Hydrodynamic Model (HM)

1B - Centre Latitude and Centre Longitude - specify the centre latitude and longitude in decimal degrees of the uninterpolated grid from the hydrodynamic model.

1C - Number of columns (ni) and number of rows (nj) - the uninterpolated grid must have an odd number of columns and rows so that the latitude and longitude of each grid node can be calculated from the centre latitude and longitude and grid cell size (1G).

1D - Adjust bathymetry grid by - if the bathymetry grid nodes are offset from the centre latitude and longitude, then use this feature to specify an offset. The offset is specified in decimal latitude and longitude.

1E - Adjust velocity data grid by - if the velocity grid nodes are offset from the centre latitude and longitude, then use this feature to specify an offset. The offset is specified in decimal latitude and longitude. In the example, the nodes of the velocity grid are offset by -0.000417 and -0.000694 degrees for Latitude and Longitude respectively. These adjustments will depend on the hydrodynamic model used.

1F - Grid cell size - this is the grid cell size of the uninterpolated grid, and may be specified in metres or fractions of a degree. In the example, cell size (x) is one 720th of a degree (= 1/720 = 0.001389).

1G - Data in - the format of the velocity data in the uninterpolated grids from the HM.

1H - Write an output file containing uninterpolated data - this feature can be used to write a file containing uninterpolated data which can then be used to check interpolations. This feature should be used occasionally - see 2B - Write an output file containing uninterpolated data.


1I - Grid size and position information for creating AD compatible velocity grids - interpolated data  - this is the information for the interpolated grids which will contain the interpolated velocity data. The grid dimensions and node positions match the AutoDEPOMOD grid. When Bathymetry is set up in AutoDEPOMOD in the usual manner using the Edit Cages button, minor grid files are created automatically shown in the AD main dialog. This is verified by the AD message 'Gridgen files exist'.



The numbers of columns and rows and cell dimensions can be loaded manually, or loaded from an AD minor grid file using the Get from .dat file button:

Example file Description Format I/O?
velgridinstalldir\Example files\Velocity grids\sitename2\DEPOMOD\Gridgen\sitename2-min.dat
 Minor grid file created by AutoDEPOMOD Edit Cages feature Space I

1J - AD origin OS Easting and Northing - this is the AutoDEPOMOD origin specified in the gridgen .ini file (C:\SEPA Consent\DATA\sitename\depomod\gridgen\sitename.ini) and also in cell P36 and 37 in the Cage Layout sheet (C:\SEPA Consent\DATA\sitename\sitename-FFMTv3.0.xls). Velgrid adds half of the cell resolution to the AD origin to calculate the position of the first node on the interpolated grid. e.g. if cell resolution is 25 m, then 12.5 m is added to origin in both directions (towards north and east).

1K - File to write out velocity grid node NGR positions - file A - Velgrid calculates the interpolated grid node positions from the information specified in 1H, 1I and 1J and writes them out to the file specified. The user should then use third party software to convert interpolated grid node NGR positions to latitude and longitude. Velgrid cannot undertake this conversion.

Example file Description Format I/O?
velgridinstalldir\Example files\Velocity grids\sitename2\AD grid nodes\AD grid nodes NGR.csv Contains NGR positions for interpolated grid nodes CSV O
i, j, OS Easting(i,j), OS Northing(i,j)

1L - File which contains velocity grid Long (col 3) and Lat (col 4) positions created from third party software - file B - Load in the file containing interpolated grid node Latitude and Longitude positions.  These node positions are used to interpolate from the HM grid created in 1B - 1F.

Example file Description Format I/O?
velgridinstalldir\Example files\Velocity grids\sitename2\AD grid nodes\AD grid nodes LatLong.csv Contains Latitude and Longitude positions for interpolated grid nodes (created from third party software) CSV I

i, j, longitude(i,j), latitude(i,j)


1M - Specify current velocity grid files from Hydrodynamic Model (HM) to be interpolated - load in files from the HM containing current velocity u and v components. The header lines are ignored during reading of data. These files have a specific format (see details), which consists of 2 grids in the same file: the first grid contains velocity u components followed by a second grid containing velocity v components. The number of columns and rows in each grid is specified in 1C. One file is loaded for each time step, and the following naming convention is recommended:

`, where tttt is a sequential number e.g. 0347 to 0706 for 360 files, *-tttt-m.dat for mid water files and *-tttt-b.dat for near-bed files. There will be 360 surface files, 360 mid water files and 360 near-bed files in a normal setup, one file for each hour of a spring-neap cycle.  Only two example files are shown here, where fiu_sur_0347.dat is timestep 1 and fiu_sur_0348.dat is timestep 2.

Depending on the HM in use, some manipulation may be required to achieve these formats. Alternatively, Velgrid code may be modified to accept different formats (see Obtaining the Velgrid code).

Example file Description Format I/O?
velgridinstalldir\Example files\Velocity grids\sitename2\surface\fiu_sur_0347.dat
velgridinstalldir\Example files\Velocity grids\sitename2\surface\fiu_sur_0348.dat

Example files are also given for mid and near bed currents in the mid and near bed sub-folders

Notes
Units of the velocity specified in 1G
Number of columns (ni) and number of rows(nj) specified in 1C
Grid is north up, right hand side of the grid is east, bottom south and left is west		 Contain uninterpolated current velocity u and v components taken from the HM (the Velgrid code is available if users wish to manipulate data input routines to the HM in use.

NOTE  - each file contains u and v components, without a space between the grids		 Space I
{Header line - ignored by Velgrid}
u(1, nj)  .. u(ni, nj)
..
u(1,1)  ..  u(ni, 1)
v(1, nj)  .. v(ni, nj)
..
v(1,1)  ..  v(ni, 1)

1N - AD compatible velocity grid files -  interpolated data - these are the files that will be created by Velgrid containing interpolated velocity data. The size of the grids in these files will equal that specified in 1I. The position of each grid node will equal those specified in the file 1L. It is these files that are loaded into ADv3 and used as spatially varying flow fields.

Example file Description Format I/O?
velgridinstalldir\Example files\Velocity grids\sitename2\surface\fiu_sur_0347_A_interpol.prn
velgridinstalldir\Example files\Velocity grids\sitename2\surface\fiu_sur_0348_A_interpol.prn

Example files are also given for mid and near bed currents in the mid and near bed sub-folders

Notes
Units of the velocity specified in 1O
Number of columns (ni) and number of rows(nj) match the size of the AD grid specified in 1I
Grid is north up, right hand side of the grid is east, bottom south and left is west		 Contains interpolated current velocity u and v components which will be used by ADv3 Space O
{Header line - ignored by Velgrid}
u(1, nj)  .. u(ni, nj)
..
u(1,1)  ..  u(ni, 1)
v(1, nj)  .. v(ni, nj)
..
v(1,1)  ..  v(ni, 1)

1O - Data out format - this is the format of the interpolated, current velocity data and should be cm/s for ADv3 compatibility.

Additional features (see Diagram D)

1P - Create grids which are not spatially varying and use the position below - this feature can be used to create ADv3 compatible velocity grids which contain velocity data for one specified position;  grids created using this feature will have the same velocity for each grid node. This feature is not used in a normal set up, but has its uses (see Create grids which are not spatially varying for details).

1Q - Creating a grid with zero current velocity - an area of the grid can be created containing zero current velocity. This is not used in a normal set up, but is useful for creating imaginary deposition centres in the grid (see Creating a grid with zero current velocity for details).

1R  - Run model and Exit - when hitting Run model, the user is asked how to save the existing information in this dialog. By saving this information, the user can reload it at another time or use it as a basis for another scenario:

Yes -  the information in the dialog will overwrite the existing stored information In the example, the information is stored in the file:

velgridinstalldir\Example files\Velocity grids\sitename2\surface\surface.ini

This file name is specified at the top of the dialog labelled 1S in Figure 1.
No - user will be prompted to specify another file name
Cancel No action is taken

1S - the name of the file where all of the information is stored in the dialog

Once the user has created ADv3 compatible velocity grid files using Velgrid, an INI file needs to be created which interfaces ADv3 with these velocity grid files - see Creating a Velgrid INI file for AutoDEPOMOD and Diagram C - Creation of Velgrid INI file.

Diagram A - Overview of AutoDEPOMOD (AD) version 3
Diagram B - Use of Velgrid
Diagram C - Creation of Velgrid INI file
Diagram D - Additional features of Velgrid

Getting started and contents