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The mesh grid structure defined here (see Tiling an image) is used by more than one program. Therefore in order to avoid repetition, all the options to do with the mesh grid (and are shared by all the programs using it) are listed here.
Some programs might define multiple meshs over the image (for example in NoiseChisel, there is a large and a small mesh for different operations, see NoiseChisel), in such cases, the options for each mesh are designated by an appropriate prefix. For example in NoiseChisel the small and large mesh sizes are specified through the --smeshsize and --lmeshsize respectively. Both these options are similar to the --meshsize option explained below, but for their respective grid. Note that the short option name might also differ. If such options exist in a program, they are listed in the ‘Invoking ProgramName’ section within the list of options.
(=INT) The size of each mesh, see Tiling an image. If the width of all channels are not an exact multiple of the specified size, then the last mesh on each axis will have a different size to cover the full channel.
(=INT) The number of channels along the first FITS axis (horizontal when viewed in SAO ds9). If the length of the image is not an exact multiple of this number, then the program will stop. You can use ImageCrop (ImageCrop) to trim off or add some pixels (blank pixels if added, see Blank pixels) to the image if it is not an exact multiple.
(=INT) The number of channels along the second FITS axis, (vertical when viewed in SAO ds9). Similar to --nch1.
(=FLT) Fraction of extra area on the last (rightest on the first FITS axis and highest/top on the second) mesh, to define a new (smaller) one. See Tiling an image.
An image with suffix _mesh.fits will be created for you to check the mesh grid, see Tiling an image. The input image will be the first extension, followed by an extension, where each pixel is labeled (number starting from zero) by the ID of the mesh it belongs to. If the program uses multiple mesh grids, the output will have more than two extensions. By flipping through the extensions, you can check the positioning and size of the meshs.
(=FLT) The distance beyond the mirror point (in units of the error in the mirror point) to check for finding the mode in each mesh. This is part of the process to quantify the presence of signal in a mesh, see Quantifying signal in a mesh. See appendix C in Akhlaghi and Ichikawa (2015) for a complete explanation of the mode-finding algorithm. The value to this option is shown as \(\alpha\) in that appendix.
(=FLT) The minimum acceptable quantile for the mode of each mesh. The median is on the 0.5 quantile of the image and as long as we have positive signal (all astronomically relevant observations), the mode will be less than the median. The sky value is only found on meshes where the median and mode are approximately the same, see Sky value.
Only interpolate the blank pixels. By default, interpolation will happen on all the mesh grids, not just the blank ones. See Grid interpolation and smoothing.
(=INT) The number of nearest grid elements with a successful sky value to use for interpolating over blank mesh elements (those that had a significant contribution of signal), see Grid interpolation and smoothing.
Do interpolation irrespective of the channels in the image, see Grid interpolation and smoothing.
(=INT) The width of the average filter kernel used to smooth the interpolated image in units of pixels. See Grid interpolation and smoothing. If this option is given a value of 1 (one), then no smoothing will be done.
Do smoothing irrespective of the channels in the image, see Grid interpolation and smoothing.
Store the fixed value in each mesh in one check image pixel, see Checking grid values. Note that this image has no world coordinate system.
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GNU Astronomy Utilities 0.2.28-34fb manual, October 2016.