Layers

The Layer is the basic unit of data and display in Openwind. Layers in Openwind are modelled on the concept of layers in geographical information systems (GIS) such as MapInfo and ArcGIS and, in fact, the vector layers in Openwind were created specifically to contain and display the information contained in ESRI Shape files.

All layers in Openwind are displayed in the left hand panel of the interface, next to the map-viewing panel (referred to from now on as the map-view). We call this left hand panel the tree-view. New layers can be created by right-clicking in the empty space in the tree-view and selecting New Layer. Users may then take advantage of subsequent pop-up menus to select which type of layer they wish to create.

Layers can be shown in the map-view or hidden by checking or un-checking the box before the appropriate name.

The layer menu can be accessed by right-clicking on any currently visible layer. The options available in the layer menu will vary according to the layer type and place in the hierarchy but can contain the following options:

• Zoom to Layer - attempts to set the extents of the map-view to match the extents of the layer

• Enable - enables a disabled Site Layer

• Disable - disables a Site Layer

• Export to RSF - exports a WAsP RSF file based on the currently selected Site Layer, Gridded Turbine Layer or Sensor Grid Layer

• Create Site Layer- creates a new turbine layout ( Site Layer ) based on the currently selected Point Layer locations

• Create Environmental Sensors - creates a new Environmental Sensor Layer based on this Point Layer locations.

• Create Substations - creates a new Substation Layer based on the currently selected Point Layer locations.

• Create Grid Connects - creates a new Grid Connection Layer based on the current Point Layer locations.

• Create Obstacles - creates a new Obstacle Layer based on the currently selected Point Layer locations. See Site Calibration (Power Curve Test)

• Create Default Met Mast Layers - creates a default Met Mast Layers at each point in the currently selected Point Layer

• Create Gridded Turbine Layout - creates a new Gridded Turbine Layout based on this Polygon Layer

• Create Sensor Grid Layer - creates a new Sensor Grid Layout based on this Polygon Layer

• Create Environmental Polygon Sensors - creates a new Environmental Sensor Polygon Layer based on this Polygon Layer

• Rasterise to obstacles - create an Obstacle Point Layer with point obstacles objects filling in the polygons in the currently selected Polygon Layers

• Convert to WRG - creates a new WRGLayer object based on this Wind Map Layer by fitting Weibulls to the data in the first child met mast and scaling by the mean wind speeds in the Wind Map Layer.

• Calculate - triggers the calculation of a Wind Map Layer

• Stop Calculation - stops the calculation of a Wind Map Layer

• Convert to WindMap - uses mean wind speeds, terrain elevation and directional probabilities to construct a Wind Map Layer object.

• Create TI Layer (ESDU 1985) - creates a directional raster of TI based on the method outlined in ESDU 1985. This method combines the currently selected wind speed raster with a roughness raster in order to create a directional raster of mean TI based on the extent, number of directions and heights in the wind speed raster.

• Calculate WAsP RIX – only applicable to point layers. Calculates the ruggedness index relative to each point in the point layer (site layer, met mast layer etc.) and stores the results to the layer attributes. When using a terrain raster, Openwind will sample at regular intervals but when using a Line Layer for terrain elevation (i.e. contours) Openwind will use line crossing in order to emulate the WAsP method more closely.

• Remove - deletes the currently selected layer from the workspace and from memory along with all child layers

• Copy - creates a copy of the current layer and adds it to the workspace

• Copy All - creates a copy of the current layer along with all its children and adds them to the workspace

• Export - allows a user to save a layer in an external format (e.g., a polygon layer could be saved as a Shape file). The export dialog allows the exported file to be in a different EPSG projection.

• Save As JSON or XML.. - This saves the layer as a JSON or XML file. This is primarily intended for use with the Openwind API ( HTTP Server Mode )

• Load from JSON or XML.. - This allows the layer that has been saved as JSON or XML to be loaded back into Openwind. ( HTTP Server Mode )

• Export Separation Distances - allows the circles, ellipses or custom separation distances between turbines in this Site Layer to be exported as a shape file. In the case of circles and ellipses it is half the separation distance, the same as is displayed on screen.

• Export Wind Resource Files - Exports to a folder all used WRGs and met mast layers as well as wind speed rasters based on the currently selected Site Layers or Gridded Turbine Layer

• Rasterise Turbine Results - Creates a directional raster of the energy capture results stored in the currently selected Sensor Grid Layer

• Save As - saves a layer in Openwind native format (this is useful for exchanging between different instances of Openwind although of course you can drag and drop between instances as well.)

• Merge With Parent - this option is available only for vector layers ( Point Layers, Line Layer, Polygon Layer ) and only when they contain compatible data fields

• Crop parent to this valid area - crops the parent vector layer to the valid area of the currently selected layer. Crude capability and mostly superseded by the crop tool.

• Back-Calculate Shadow Flicker Validity - prompts the user to select a turbine type and then creates a grid of positions with the chosen turbine type at each grid node. The value at each node is 100 for those turbine positions which do not violate the shadow flicker minutes limit at any Environmental Sensor and zero for those positions that do violate a limit.

• Back-Calculate Shadow Flicker Minutes - prompts the user to select a turbine type and then creates a grid of positions with the chosen turbine type at each grid node. The value at each node is the number of shadow flicker minutes caused by the chosen turbine type being at that grid node location. If the same turbine position causes simultaneous shadow flicker at two locations then those minutes are counted only once.

• Back-Calculate Shadow Flicker Shutdown Loss - prompts the user to select a turbine type and then creates a grid of positions with the chosen turbine type at each grid node. The value at each node is the fraction of a year that the chosen turbine type would need to be shut down in order to meet the shadow flicker limits at the surrounding Environmental Sensors.

• Change Selected Height - allows the user to change the selected mast height. Only really useful for multi-height Met Mast Layers.

• Create Uncertainty Raster - applies to WRGLayers and uses the uncertainty relationship defined in the uncertainty settings to estimate the uncertainty in a WRG relative to a single mast location.

• Remove Wake Effects - modifies the currently selected Met Mast Layers in an attempt to back out the wakes that that met mast would have experienced during the measurement period, based on the current wake model settings (see Remove Wake Effects as well as Site Layer Dates)

• Suggest New Masts - makes use of the uncertainty relationship defined in the uncertainty settings to find the highest point of uncertainty within the currently valid area of this WRGLayer and suggests a mast at that location. It will take into account multiple child met masts while doing this. It is important to restrict the valid area of the WRGLayer to only those parts of the project where you would seriously consider placing turbines or met masts as this function will tend to just find the parts of the site that are least represented by the current met masts.

• Create Validity Rasters - makes use of the uncertainty defined in the uncertainty settings to create a validity raster for each met mast. Only one met mast is marked as valid at any one point and that is determined as the met mast whose uncertainty is lowest at that point. The intention is then that each met layer and validity raster will be partnered with a copy of the parent WRGlayer

• Create Uncertainty Raster - creates wind-flow uncertainty rasters based on the currently selected Wind Resource Grid, for each of its child Met Mast Layers using the current Uncertainty settings.

• Make WRG Copies & Assign Met Masts - this does the same as the in the adjust to masts dialog in the sense that it creates the same number of copies of the WRG or Windmap as there are child met mast layers and then creates Voronoi polygons as a way of assigning the land closest to each met mast as its valid area.

• Recreate Display Layers - this option is only available for Wind Resource Grids in order to recreate layers based on the data contained in the WRG

• Initialise Wind Map Run - this option is designed to take an already created Wind Resource Grid and allow it to be down-scaled to a finer resolution using the wind-flow model in Openwind. It does not require a met mast as the initial wind field is initialised from the WRG.

• Adjust WRG to wind speed map - this option allows a Wind Resource Grid to be adjusted so that the mean wind speeds match the values in a wind speed map. The wind speed map must be a child of the WRG and must have its units set to meters per second [m/s]

• Extract Single Layer WRG - Creates a new simple WRG or WindMap based on a single case and height in the clicked WRG or WindMap.

• Shear New Height (in this WRG) - Shears a new height in the clicked WRG or WindMap, based on the calculated mean shear for each direction. Does not create a new object but adds to the current object.

• Remove Height (in this WRG) - Removes a height from the clicked WRG or WindMap.

• Average WRGs - This averages the values in the Wind Resource Grids which are children of the Folder Layer. It is different from merging in that there is no distance weighting relative to met mast locations.

• Average Wind Maps - This averages the values in the Wind Maps which are children of the currently selected Folder Layer. It is different from merging in that there is no distance weighting relative to met mast locations.

• Merge WRGs - when there are multiple Wind Resource Grids covering the same area and as children of the Folder Layer that was right-clicked upon, this option will appear. It allows users to merge multiple WRGs using an inverse distance-squared weighting and is only included as a means to reassure users that adjust to mast and merging are more or less equivalent (although of course adjust to mast is the more correct of the two in cases where there are significant directional shifts across the WRGs).

• Merge WindMaps - this is the equivalent of the above function for Wind Map Layers

• Create Multi-Dimensional WindMap - right-click on a Folder Layer to see this menu option which will only be available if the child Wind Map Layers have the same horizontal extents, grid spacing and number of sectors. Wind Map Layers can be combined to create either a multi-height (from single height WRGs) or time-queryable compound object.

• Create Multi-Dimensional WRG - right-click on a Folder Layer to see this menu option which will only be available if the child Wind Resource Grids have the same horizontal extents, grid spacing and number of sectors. WRGs can be combined to create either a multi-height (from single height WRGs) or time-queryable compound object.

• Adjust to Mast(s) - this allows a single WRG or WindMap to be adjusted to match (or incorporate the influences of) several met mast layers. Please see Section 51 for a more in depth look at adjust to mast. Once a WRG has been adjusted to multiple masts, it can be copied so that each met mast layer has its own copy of the WRG. The valid area of each of these WRGs then needs to be restricted by the user so that each met mast only applies to the area for which the user deems it appropriate.

• Extract Point WRG(s) at mast location - creates a single point WRG at mast location(s), from the values in the parent WRG. This functionality is deprecated as point WRGs are no longer required with recent improvements to the Energy Capture Settings

• Do mast speed cross-predictions - creates an on-screen report of the errors when using a WRG or WindMap to predict each mast from every other mast. The exact method is described in the report itself.

• New Layer: Transform This Layer - creates a new RasterLayer by applying a simple arithmetic operation to all the Z values in the current Raster Layer

• New Layer: Ruggedness Index - creates a new multidimensional Raster Layer representing upstream terrain ruggedness based on either a Line Layer or Raster Layer interpreted as terrain elevation. This is largely of interest to WAsP users. When using a LineLayer for terrain elevation (i.e. contours) Openwind will use line crossing in order to emulate the WAsP method more closely.

• Export to WAsP - this menu item is available when right-clicking on either terrain contours or a roughness raster. It will output the terrain or roughness as a WAsP map with no dead-ends, cross points or inconsistencies. If there is a terrain isoline layer in the same hierarchy as a the roughness layer, or vice versa, this function will export both in the same map file.

• Resample - creates a new raster based on the currently selected raster layer but resampled at the chosen resolution.

• New Layer: Create isolines - this function works well for noise contours and other smooth mathematically generated surfaces but less well for terrain contours. However, it must be stated that whilst the terrain contours it generates are not pretty, they are technically correct and will work fine when imported into WAsP say.

• Filter this layer - again this function was added as a way to facilitate comparisons with WAsP. Whilst WindMap averages upstream roughness in bands, WAsP counts individual roughness changes and so it is generally not a good idea to export real-world roughness data to WAsP. This function applies a filter to the roughness raster which should be used before exporting to WAsP. The filter can be applied repeatedly until the roughness map looks like something one would see in WAsP. It effectively pushes area of the map to consolidate into one value or another.

• New Layer: Displayed Grid - creates a new Raster Layer based on the currently displayed direction of a multidimensional Raster Layer

• New Layer: Averages - creates a new Raster Layer by averaging (over all directions) a multidimensional Raster Layer

• New Layer: Minimums - creates a new Raster Layer by taking the minimums (over all directions) of a multidimensional Raster Layer

• New Layer: Maximums - creates a new Raster Layer by taking the maximums (over all directions) of a multidimensional Raster Layer

• New Layer: Sum With Parent - creates a new Raster Layer by summing values in two existing Raster Layers

• New Layer: Subtract Parent - creates a new Raster Layer by subtracting values in the parent layer from those in this layer

• New Layer: Subtract From Parent - creates a new Raster Layer by subtracting values from those in the parent layer

• New Layer: Min with Parent - creates a new Raster Layer by taking the minimum of this layer and the parent layer at each point in the grid

• New Layer: Max With Parent - creates a new Raster Layer by taking the maximum of this layer and the parent layer at each point in the grid

• Make Wind Map Layer - creates a Wind Map Layer based on the probabilities and average wind speeds in a WRG

• Repair All Child Met Time-Series Data - if there are more than one child Met Mast Layer containing time-series data, this option allows the simultaneous repair of all of them using the same settings.

• Reset Grid - the currently selected Gridded Turbine Layers is repacked with minimum spacing. This can be useful for re-running an Optimisation of a gridded site layer.

• Show Children - makes all child layers visible

• Hide Children - makes all child layers invisible

• Properties - triggers the layer properties dialog

• Cancel - deactivates the layer menu without choosing any of the above options

Of course, no one layer will ever present all these options.

Basic GIS layers in Openwind fall into two categories: raster layers (known as RasterLayers ) and Vector Layers (known as Point Layers, Line Layers and Polygon Layers ).

The properties of any layer can be accessed by right-clicking on that layer in the tree-view and choosing Properties or, alternatively, double-clicking the left mouse button on the layer in the tree-view.

For the properties of each layer type, please see our section on that particular layer type.

Openwind makes use of the data within layers by way of three simple concepts:

• Layer Validity - this is the idea that one layer can be used to affect the valid spatial range of another layer.

• Interpretation - the capability to assign a physical meaning to the values in a layer.

• Search Order - Openwind has a rigid search order which allows the user control over which data layers are used for what purpose.