Project Design Grid - Underwriters-Labs/renewables.openwind.help GitHub Wiki
The project design grid format can contain all the same data as a WRG. But it can also contain: roughness; inflow angles; turbulence intensity variation across the site; wind shear exponent and so on.
Header structure
| Start Byte | Number of Bytes | Type | Description | Comments |
|---|---|---|---|---|
| 0 | 2 | unsigned short | File type | 1001 = BINARY WRG – non-interleaved, uncompressed. |
| 2 | 2 | unsigned short | Version | Version of this type of file current = 2 |
| 4 | 1 | byte | Horizontal units | 1 = meters |
| 5 | 1 | byte | Vertical units | 1 = meters |
| 6 | 30 | character | Characters describing datum projection as an EPSG code | e.g. "EPSG:32619" is the best way to specify WGS84, UTM 19 |
| 36 | 2 | Unsigned short | Number of directions | e.g. 12 |
| 38 | 2 | Unsigned short | Number of heights | e.g. 1 |
| 40 | 2 | Unsigned short | Number of wind speeds | Unused(default) = 0 |
| 42 | 8 | double | X min | Rectangle describing bounding grid points. Covered area is res/2 larger in all directions |
| 50 | 8 | double | X max | |
| 58 | 8 | double | Y min | |
| 66 | 8 | double | Y max | |
| 74 | 8 | double | Resolution in X | |
| 82 | 8 | double | Resolution in Y | Usually same as res X |
| 90 | 2 | Unsigned short | Total Number of blocks | Block descriptions start at byte 100. each block description is |
| 92 | 8 | byte | Unused | |
| 100 | 2 | Unsigned short | Data meaning for block index 0 | 1 = elevation,2 = mean wind speed3 = A4 = K5 = Power6 = Turbulence Intensity7 = Inflow angle8 = Probability (for wind freq table at every point)9 = Direction10 = Surface roughness11 = Air Density12 = Vertical velocity13 = Wind Shear exponent |
| 102 | 4 | float | Height for this block (above ground level) | Default or N/A = -1 |
| 106 | 2 | short | Direction for this block | -1 means not directional. Directions start at 0 = north and work clockwise |
| 108 | 4 | float | Wind Speed for this block | -1(default) means not by wind speed |
| 112 | 8 | Double | Probability for this block | Usually 1.0 (P<1.0 can be used to specify that this is one of multiple wind regimes each having its own probability) |
| 120 | 4 | Int32 | ID for this group of blocks | Usually set to 0 – unused (can be used with P to specify multiple wind regimes within one file) |
| 124 | 8 | Int64 | Offset of this block in this file | Start byte |
| 132 | 1 | byte | Data type | 0 = float (default)1 = double2 = byte3 = short4 = long (32 bit) etc |
| 133 | 2 | Unsigned short | Unit (new) | 0 = none (default)1 = m2 = m/s3 = degree (+/-180)4 = degree (0 - 360)5 = % |
| 135 | 29 | byte | unused | |
| 100 + block index*64 | 2 | Unsigned short | Data meaning for block index 1 | |
| …. |
Constraints are:
- All directional blocks contain same number of directions
- All blocks have same horizontal resolution
- All blocks share same horizontal grid points
- All blocks share same number of directions (if directional)
- If units are not appropriate for meaning, units are ignored
Block Structure
Each block is ordered in lines of X starting the bottom left hand corner. All values are stored as 4 byte floats by default.