A. The area around the site that you need to input to WAsP, depend very much on the type of roughness changes that are present. Usually, it is necessary with roughness maps that extend to at least 5-10 km from the site. If there are extensive water surfaces or other significant roughness changes further away, it may even be extended to 10 km or more. The orography map should also extend to at least 5-10 km from any site.

Q. Must height contours be closed in a digital map?

A. No, not in general. WAsP is rather tolerant regarding height contours, as the elevation for points between height contours are inferred by interpolation. Height contours may end blindly e.g. at the map boundary, or at the boundary of a high-resolution area surrounding a point of interest (met. mast or wind turbine location.), where the height contour interval changes from e.g. 5 m to 20 m.

Q. Must roughness lines be closed in a digital map?

A. No, not in general – but they cannot just end as “blind ends”. Roughness lines must either form a closed loop; or the end points must be located at a “node” point (where 3 or more roughness lines meet in a star); or on the map boundary.

Q. What is the max. number of points in a WAsP map (*.map)?

A. The max. number of points allowed in a single map is about 1,000,000. WAsP will load larger maps when you use the option "Insert from file | Vector map" – without any warning or error message – but it cannot display it properly, nor can it be used for calculating wind atlases or wind climates.

Workaround: Open the map in the Map Editor and reduce its size to below 1,000,000 points – either by "Lines thinning", by reducing the extent of the map; or by splitting the map in separate parts. Line thinning is an Edit menu option; use it with a precision of, say, 1, 2 or 5 m. The map extent may be reduced by the the menu Edit option "Clip | Map part", which is also used for splitting the map. Map splitting could be performed e.g. so that one map contains the terrain around a met. station, and others the surroundings of wind farms or containing the area of a resource grid. Remember that the map extension should be out to at least 5-10 km from any site of interest (met. station, wind turbine, resource grid point).

Q. How do I import files from programs like Surfer, Didger and Autocad?

A. Files produced by Surfer or Autocad are loaded as standard files. This means that you click "Open" under the file menu (in the Map Editor) and then you can choose the file type to be: *.map, *.bna (Surfer or Didger files) or *.dxf (Autocad files).

Q. How do I represent spot heights?

A. We recommend that you represent a spot height by a circle with a diameter of 5-6 m. This is quite easy and also what the latest version of the Map Editor will do for you. When you edit your map with single-point spot height in the Map Editor it converts single-points to small spot height-circles.

Q. What value should I assign to the roughness length (z₀) for water in WAsP?

A. The roughness of water must be given as 0 (zero) in order for WAsP to distinguish between water areas and very smooth land surfaces. (Internally, WAsP uses 0.0002 m for a water surface, but the user should specify 0).

Q. How do I convert a grid elevation map or a DXF-map to WAsP-formatted map?

A. It is in fact rather simple! First of all, the latest map editor version can open dxf-format map files directly (use the menu point File | Open and select the file type DXF-format maps) – and you may then afterwards save the map as a standard WAsP digital map (*.map). Grid map files (containing terrain elevation information at the nodes of a regular grid): these may be converted to dxf in Surfer. Create a contour map using the grid file, then afterwards save this contour map as *.dxf using the menu point " Map | Contour map | Export contours ". Then, use the map editor to convert this file to a WAsP *.map file.

Q. How can I generate a WAsP map from gridded data or spot heights?

A. The Surfer program can make a contour map of an area from spot heights given in a regular grid; a so-called digital elevation model (DEM). The grid data may be input directly or it can be generated by Surfer from irregularly spaced spot heights. The Surfer program can further be used to edit the map contents, e.g. the map limits and contour interval. The height contours of the map can be exported as a 3-D DXF-file from Surfer's Map menu (Contour Map | Export Contours). This DXF-file can be converted into a WAsP MAP-file by the WAsP Map Editor.

Gridded height data can also be transformed directly into a WAsP MAP-file using the WAsP Utility Program grd2map.exe. This program reads Surfer ASCII GRD-files and writes WAsP MAP-files. The vertical contour interval and elevation range for extracted contours may be specified by the user.