The Vector Field renderer uses vector symbols to display raster data. This renderer is often used for visualizing flow direction and magnitude rasters, in meteorology and oceanography. The direction of the raster defines the angles, while the magnitude raster defines the size of the symbol. It can also be used to symbolize a single raster layer where the symbols are scalar. Below, the first image renders with the directional view raster. The next image is the same raster with the magnitude view of the raster. The third image is the same raster with a vector field renderer applied, which shows magnitude and direction at the same time.
The input for this vector field renderer can be mosaic layers, raster layers, and netCDF raster layers. The flow direction and magnitude data can be stored in one dataset as two bands or two separate datasets.
The data may also be captured as U and V components that the renderer converts to magnitude and direction on-the-fly during rendering.
The Vector Field renderer draws each symbol within a defined tile size, where the tile size controls the density of the displayed vector symbols. The size of the symbol is determined by the tile's magnitude value and the direction of the symbol (arrow) is determined by the tile's direction value. As each tile may contain many pixels, the tile's magnitude and direction values resample using a thinning method. The images below show two different tile sizes. The image on the left shows each symbol representing 50 screen pixels. The image on the right shows each symbol representing 100 screen pixels.
The minimum and maximum symbol sizes are used to adjust the symbol size to the tile:
Parameter description of the Vector Field renderer
This check box determines if the input components represent magnitude/direction or U/V.
Magnitude or U
The input magnitude or U component—It can be a band from a multiband raster dataset (including a mosaic dataset), a separate raster layer, or a netCDF raster layer.
If Direction is not provided (set it to None), a scalar value displays. In this case, the symbol only resizes—no rotation occurs. This case can be used to visualize data such as salinity or dissolved oxygen.
In the case where U is used, the renderer converts to magnitude, on-the-fly.
Direction or V
The input direction or V component—It can be a band from a multiband raster dataset (including a mosaic dataset), a separate raster layer, or a netCDF raster layer.
If Magnitude is not provided (set it to None), the renderer draws the data with a rotation but with a constant size applied. This is useful to visualize data like aspect.
In the case where V is used, the renderer converts to direction on-the-fly.
Specifies how the direction component was measured.
Specifies the direction of mass flow.
Choose the symbol to display your vector field. You have three ways to choose your symbol:
Specify the tile size in screen pixel units or other measurement units. The tile size determines the density of the symbols; the larger tile size, the fewer symbols appear in the display.
The thinning method is used to calculate the magnitude and direction value of a tile.
The minimum magnitude value. By default, this value is calculated from the input. You may want to modify the minimum magnitude if the input does not have statistics calculated, or the input is U and V components. Tiles with magnitude less than or equal to this value will be rendered with the minimum symbol size.
Minimum symbol size
Specify the minimum symbol size. It is specified as a percentage of the tile.
The maximum magnitude value. By default, this value is calculated from the input. You may want to modify the maximum magnitude if the input does not have statistics calculated, or the input is the U and V component. Tiles with magnitude greater than or equal to this value will be rendered with the maximum symbol size.
Maximum symbol size
Specify the maximum symbol size. It is specified as a percentage of the tile.
Following is an example of the Vector Field layer symbology dialog.