GAMMA Interferometric Point Target Analysis Software (IPTA): Reference Manual

pt2data

ANSI-C program: pt2data.c

NAME
pt2data - vector to raster format conversion (interpolate point data values into a 2-D data file / uses SLC/MLI parameter file as input)

SYNOPSIS
pt2data <plist> <pmask> <SLC_par> <pdata> <rec_num> <f_out> <par_out> [type] [imode] [radius] [np_min]

EXAMPLE
pt2data plist pmask 19990421.rslc.par punw 4 19990421_19990422.unw 19990421.rmli.par 2 2

A 2-D image (float, geometry defined by 19990421.rmli.par) is generated by interpolation (using 6 point bilinear interpolation method) of the point data values defined in record 4 of the point data stack of unwrapped phase values punw. The point list plist contains the point coordinates. No point data stack of mask values is provided.

A 2-D image (float, geometry defined by 19990421.rmli.par) is generated by interpolation (using nn_convol interpolation method with a maximum window radius of 7.5 pixel and a minimum number of 5 points) of the point data values defined in record 4 of the point data stack of unwrapped phase values punw. The point list  plist contains the point coordinates and the point data stack mask values.

A 2-D image is generated from the point data values defined in record 4 of the point data stack of unwrapped phase values (punw). No interpolation is applied, i.e. values are 0.0 (NULL) except for the point list coordinates. The point list contains the point coordinates.

pt2data supports the conversion of image data from the IPTA vector data format to the "normal" 2-D raster image format.

The input vector data is defined by the point list, the point data stack, the related record number, and the SLC parameter file of the point list coordinates. In addition, a point data stack of mask values can be indicated which specifies for each data point a zero or non-zero flag which is interpreted to ignore or consider a certain data point.

The output image can either be in the SLC geometry used for the point list coordinates or in a multi-looked geometry (relative to the same SLC geometry, without offsets in range and azimuth) as defined in the related SLC/MLI parameter file.

Different data types (fcomplex, scomplex, float, int, short, byte) are supported. The data type of the output 2-D image data corresponds to the indicated data type of the input point data stack. For interpolation mode 0 (none) the output 2-D image data has non-zero values only at the point list coordinates. No interpolation is applied.

For the interpolation modes 1 to 4 output values are also determined for coordinates other than the point list coordinates. Some interpolation modes also modify (filter) the values at the point list coordinates.

In the interpolation modes 1 (3-pt_bilinear) and 2 (6-pt_bilinear) the three, respectively six, neighboring points of the Delaunay Triangulation Network are considered for the interpolation. A bilinear interpolator is used. These interpolators are spatially adaptive - the number of neighbors used is kept constant but the area considered may significantly vary. At the point list coordinates the output value corresponds to the corresponding to point data value, i.e. these values are not filtered.

In the interpolation mode 3 (convolution) the indicated window radius and minimum number of points are considered. For pixels which do not have the minimum number of point list coordinates within the indicated indicated window radius the output value is set to the NULL value. For pixels with a sufficient number of point list coordinates in their neighborhood a convolutional interpolator is applied. The same procedure is also applied for pixels corresponding to point list coordinates, i.e. these values are filtered.

In the interpolation mode 4 (convolution of nearest neighbors) the indicated window radius and minimum number of points are considered. For pixels which do not have the minimum number of point list coordinates within the indicated indicated window radius the output value is set to the NULL value. For pixels with a sufficient number of point list coordinates in their neighborhood a convolutional interpolator is applied, but only considering the values at the np_min nearest neighbors. This results in a spatial adaptivity with small windows used in areas of dense point occurrence. The same procedure is also applied for pixels corresponding to point list coordinates, i.e. these values are filtered.

In the case a point data stack of mask values is indicated, point data values which are masked (i.e. uchar value is 0 in the corresponding record at the corresponding position of the point data stack of mask values) are treated as NULL values at the same location. The use of such masking permits to ignore data values without needing to change the point list. Such masks can be different for each record permitting to selective deactivate individual data points.

The functionality of pt2data and pt2d are corresponding except that the output geometry is specified using an SLC/MLI parameter file in the case of pt2data while geometric parameters are directly specified on the command line in pt2d.

SEE ALSO
pt2d, SLC_par, typedef_ISP.h, ipta.h.