xyz2grd

xyz2grd(cmd0::String="", arg1=nothing, kwargs...)

keywords: GMT, Julia, grid

Convert data table to a GMTgrid type.

Description

Reads one or more x, y, z or z tables and creates a grid. It will report if some of the nodes are not filled in with data. Such unconstrained nodes are set to a value specified by the user [Default is NaN]. Nodes with more than one value will be set to the mean value. As an option (using flags), a 1-column z table may be read assuming all nodes are present (z tables can be organized in a number of formats, see flags below.) Note: xyz2grd does not grid the data, it simply reformats existing data to a grid structure. For gridding, see surface, greenspline, nearneighbor, or triangulate.

Required Arguments

• table
  A data table holding z or x, y, z values. The x, y, z triplets do not have to be sorted. One-column z tables must be sorted and the flags option must be set.

• I or inc or increment or spacing : – inc=x_inc | inc=(xinc, yinc) | inc="xinc[+e|n][/yinc[+e|n]]"
  Specify the grid increments or the block sizes. More at spacing

• R or region or limits : – limits=(xmin, xmax, ymin, ymax) | limits=(BB=(xmin, xmax, ymin, ymax),) | limits=(LLUR=(xmin, xmax, ymin, ymax),units="unit") | ...more
  Specify the region of interest. More at limits. For perspective view view, optionally add zmin,zmax. This option may be used to indicate the range used for the 3-D axes. You may ask for a larger w/e/s/n region to have more room between the image and the axes.

Optional Arguments

• A or multiple_nodes : – multiple_nodes=true | multiple_nodes="d|f|l|m|n|r|S|s|u|z"
  By default we will calculate mean values if multiple entries fall on the same node. Use this option to change this behavior, except it is ignored if flags is given. Append f or s to simply keep the first or last data point that was assigned to each node. Append l or u or d to find the lowest (minimum) or upper (maximum) value or the difference between the maximum and miminum value at each node, respectively. Append m or r or S to compute mean or RMS value or standard deviation at each node, respectively. Append n to simply count the number of data points that were assigned to each node (this only requires two input columns x and y as z is not consulted). Append z to sum multiple values that belong to the same node.

• J or proj or projection : – proj=<parameters>
  Use the proj syntax to save the georeferencing info as CF-1 compliant metadata in netCDF grids. Remember also that PROJ syntax can be used directly in proj. This referencing will be recognized by GDAL and increasingly also by GMT.

• G or save or outgrid or outfile : – outgrid=[=ID][+ddivisor][+ninvalid][+ooffset|a][+sscale|a][:driver[dataType][+coptions]]
  Give the name of the output grid file. Optionally, append =ID for writing a specific file format (See full description). The following modifiers are supported:

  • +d - Divide data values by given divisor [Default is 1].

  • +n - Replace data values matching invalid with a NaN.

  • +o - Offset data values by the given offset, or append a for automatic range offset to preserve precision for integer grids [Default is 0].

  • +s - Scale data values by the given scale, or append a for automatic scaling to preserve precision for integer grids [Default is 1].

Note1: Any offset is added before any scaling. +sa also sets +oa (unless overridden). To write specific formats via GDAL, use =gd and supply driver (and optionally dataType) and/or one or more concatenated GDAL -co options using +c. See the “Writing grids and images” cookbook section for more details.

Note2: This is optional and to be used only when saving the result directly on disk. Otherwise, just use the G = modulename(...) form.

• S or swap : – swap=true | swap=zfile
  Swap the byte-order of the z table input only. No grid is produced. You must also supply the flags option. The output is return to Julia or written to zfile

• V or verbose : – verbose=true | verbose=level
  Select verbosity level. More at verbose

• Z or flags : – flags=flags
  Read a 1-column table. This assumes that all the nodes are present and sorted according to specified ordering convention contained in flags (a string). If incoming data represents rows, make flags start with T(op) if first row is y = ymax or B(ottom) if first row is y = ymin. Then, append L or R to indicate that first element is at left or right end of row. Likewise for column formats: start with L or R to position first column, and then append T or B to position first element in a row. Note: These two row/column indicators are only required for grids; for other tables they do not apply. For gridline registered grids: If data are periodic in x but the incoming data do not contain the (redundant) column at x = xmax, append x. For data periodic in y without redundant row at y = ymax, append y. Append s n to skip the first n number of bytes (probably a header). If the byte-order or the words needs to be swapped, append w. Select one of several data types (all binary except a):

- **A** ASCII representation of one or more floating point values per record - **a** ASCII representation of a single item per record - **c** int8_t, signed 1-byte character - **u** uint8_t, unsigned 1-byte character - **h** int16_t, signed 2-byte integer - **H** uint16_t, unsigned 2-byte integer - **i** int32_t, signed 4-byte integer - **I** uint32_t, unsigned 4-byte integer - **l** int64_t, long (8-byte) integer - **L** uint64_t, unsigned long (8-byte) integer - **f** 4-byte floating point single precision - **d** 8-byte floating point double precision Default format is scanline orientation of numbers: **flags="TLa"**. The difference between **A** and **a** is that the latter can decode both date**T**clock and *ddd:mm:ss[.xx]* formats but expects each input record to have a single value, while the former can handle multiple values per record but can only parse regular floating point values. Translate incoming *z*-values via the **-i**0 option and needed modifiers.

• bi or binary_in : – binary_in=??
  Select native binary format for primary table input. More at

[Default is 3 input columns]. This option only applies to x, y, z input files; see flags for z tables.

• di or nodata_in : – nodata_in=??
  Substitute specific values with NaN. More at

• e or pattern : – pattern=??
  Only accept ASCII data records that contain the specified pattern. More at

• f or colinfo : – colinfo=??
  Specify the data types of input and/or output columns (time or geographical data). More at

• h or header : – header=??
  Specify that input and/or output file(s) have n header records. More at

• i or incol or incols : – incol=col_num | incol="opts"
  Select input columns and transformations (0 is first column, t is trailing text, append word to read one word only). More at incol

• q or inrows : – inrows=??
  Select specific data rows to be read and/or written. More at

• r or reg or registration : – reg=:p | reg=:g
  Select gridline or pixel node registration. Used only when output is a grid. More at

• w or wrap or cyclic : – wrap=??
  Convert input records to a cyclical coordinate. More at

• yx : – yx=true
  Swap 1st and 2nd column on input and/or output. More at

Geographical And Time Coordinates

When the output grid type is netCDF, the coordinates will be labeled "longitude", "latitude", or "time" based on the attributes of the input data or grid (if any) or on the colinfo or region options. For example, both colinfo="0x" colinfo="1t" and region="90w/90e/0t/3t" will result in a longitude/time grid. When the x, y, or z coordinate is time, it will be stored in the grid as relative time since epoch as specified by TIME_UNIT and TIME_EPOCH in the gmt.conf file or on the command line. In addition, the unit attribute of the time variable will indicate both this unit and epoch.

Swapping Limitations

All data types can be read, even 64-bit integers, but internally grids are stored using floats. Hence, integer values exceeding the float type's 23-bit mantissa may not be represented exactly. When swap is used no grids are implied and we read data into an intermediate double container. This means all but 64-bit integers can be represented using the double type's 53-bit mantissa.

Examples

To create a grid file from the raw binary (3-column, single-precision scanline-oriented data raw.b, use

G = xyz2grd("raw.b", region=(0,100,0,100), inc=1, flags=true, binary_in="3f")

See Also

grd2xyz, greenspline, nearneighbor, surface, triangulate