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Options: Reprojection

Matt Painter edited this page Feb 18, 2021 · 21 revisions

In reproject mode, Sanchez reprojects geostationary IR images into plate carrée projection. See Reprojection modes for details of the different reprojection options.

In this mode, the following additional options are available:

Autocrop

All modes support optional auto-cropping (-a / --autocrop) to crop target images to a tight rectangle. This option loses some source imagery, but maximises the total area.

The example below is without and with autocrop enabled:

Image with and without autocropping

No crop

All modes support no cropping (--nocrop) to perform no cropping of the target image. With this mode enabled, the output image contains a full plate carrée projection and is suitable for reprojection to a globe using an external tool.

Latitude / longitude crop

All reprojection modes support custom latitude and/or longitude crop via --lat and --long. Both take an argument of the minimum and maximum values in degrees, of the format <min>:<max>, for example:

sanchez reproject -s C:\images\goes17\fd\fc\2020-09-12\GOES17_FD_FC_20200912T210031Z.jpg -o output.jpg --lat -33.6:-48 --lon 165.1:179.3

No underlay

When rendering a single image with no underlay and a .png output file is specified, the image is rendered on a transparent background.

Image with transparent background Image with transparent background and CLUT

Full-colour reprojection

If you already have a full colour composite, use the -U / --nounderlay mode combined with -L / --noadjustlevels to create an image which has no colour correction or underlay applied.

Full-colour reprojection

The following example also preserves the original 2km spatial resolution (5424x5424px image) by using the -r 2 flag.

sanchez reproject -s C:\images\goes17\fd\fc\2020-09-12\GOES17_FD_FC_20200912T210031Z.jpg -o output.jpg -ULa -r 2

Stitching options

Time tolerance

Give a target timestamp, Sanchez identifies images which are either captured at or near the timestamp. The maximum time tolerance for determining whether an image is included is defined by -d / --tolerance and is specified in minutes. If no tolerance is provided, the default of 30 minutes is used.

Minimum satellite count

Of particular use when producing a timelapse, the minimum number number of required satellites can be specified via -m / --minsatellites. When this is set, only images are produced which contain at least the specified number of satellites.