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B.2.2 Gridline and Pixel node registration

Scanline format means that the data are stored in rows (y = constant) going from the ``top'' ($y = y_{max}$ (north)) to the ``bottom'' ($y = y_{min}$ (south)). Data within each row are ordered from ``left'' ($x = x_{min}$ (west)) to ``right'' ($x = x_{max}$ (east)). The node_offset signals how the nodes are laid out. The grid is always defined as the intersections of all x ( \( x = x_{min}, x_{min} + x_{inc}, x_{min} + 2 \cdot x_{inc}, \ldots, x_{max} \) ) and y ( \( y = y_{min}, y_{min} + y_{inc}, y_{min} + 2 \cdot y_{inc}, \ldots, y_{max} \) ) lines. The two scenarios differ in which area each data point represents. The default node registration in GMT is gridline node registration. Most programs can handle both types, and for some programs like grdimage a pixel registered file makes more sense. Utility programs like grdsample and grdproject will allow you to convert from one format to the other; grdedit can make changes to the grid header and convert a pixel- to a gridline-registred grid, or vice versa.



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next up previous contents index
Next: B.2.2.1 Gridline registration Up: B.2 Grid files Previous: B.2.1 NetCDF files   Contents   Index
Paul Wessel 2011-02-27