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kalibr_create_target_pdf renders a calibration target — either an AprilGrid or a checkerboard — to a PDF file that you can print at the correct physical scale. The output dimensions are defined by the tag or square size arguments in meters, which the tool converts to the PDF coordinate system automatically. Print the resulting PDF at 100% scale (no scaling, no fit-to-page) and measure the physical tag or square size with calipers to verify it matches the value you passed to the tool.

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Synopsis

kalibr_create_target_pdf [output] --type <apriltag|checkerboard> [options]

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Examples

kalibr_create_target_pdf --type apriltag \
                         --nx 6 --ny 6 \
                         --tsize 0.08 \
                         --tspace 0.3
This generates target.pdf with a 6×6 AprilGrid using the default t36h11 family, with 8 cm tags and 30% inter-tag spacing.To use a different output name and tag family:
kalibr_create_target_pdf aprilgrid_t25h9 \
                         --type apriltag \
                         --nx 6 --ny 7 \
                         --tsize 0.06 \
                         --tspace 0.3 \
                         --tfam t25h9

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Flags

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Output options

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output
string
Output filename without extension. The tool appends .pdf (and .eps when --eps is given). Default: target.
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--eps
boolean
Also write an EPS file alongside the PDF.

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Generic grid options

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--type
string
Grid pattern type. Accepted values: apriltag, checkerboard.
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--nx
integer
Number of tags or squares in the x direction (columns). Default: 6.
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--ny
integer
Number of tags or squares in the y direction (rows). Default: 7.

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AprilGrid options

The following flags apply only when --type apriltag is set.
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--tsize
float
Size of one AprilTag in meters. Default: 0.08.
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--tspace
float
Spacing between adjacent tags as a fraction of the tag edge size, in the range [0, 1]. Default: 0.3.
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--tfam
string
AprilTag family. Accepted values: t16h5, t25h7, t25h9, t36h11. Default: t36h11.t36h11 provides the best detection reliability and is the recommended family for Kalibr.
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--skip-ids
string
Space-separated list of tag IDs to leave blank in the grid. Useful when specific tags are damaged or known to be problematic. Default: none.

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Checkerboard options

The following flags apply only when --type checkerboard is set.
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--csx
float
Width of one checkerboard square in the x direction, in meters. Default: 0.05.
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--csy
float
Height of one checkerboard square in the y direction, in meters. Default: 0.05.

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Tag families

FamilyBitsMax tagsReliability
t16h51630Lower (more false positives)
t25h725242Moderate
t25h92535Moderate
t36h1136587Highest (recommended)
The t36h9 family is defined in the source code but commented out and not available at runtime. Use t36h11 instead.

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Generating a YAML target configuration

After printing, create a YAML configuration file that matches the physical parameters you used. Pass this file to --target in all Kalibr calibration tools. 
target_type: 'aprilgrid'
tagCols: 6
tagRows: 6
tagSize: 0.08      # meters — measure after printing
tagSpacing: 0.3    # same fraction used with --tspace

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