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How To: Interpolate elevation values for a tin clip coverage

Summary

A hull polygon coverage can be created to define the zone of interpolation. Buffering the hull polygon creates a clip coverage within the zone of interpolation. The missing z values for each clip cover arc node and vertex will be generated from the available surface using linear interpolation along the break line.

Procedure

  1. Generate a tin using the ARCTIN command. Use the TINARC command to generate a hull coverage defining the zone of interpolation.

    Code:
    Arc: ARCTIN <in_cover> <out_tin> POINT {spot_item}
    Arc: TINARC <in_tin> <out_cover> HULL

  2. Use the BUFFER command with the RIGHT option to create a polyon clip coverage just inside the zone of interpolation.

    Code:
    BUFFER <in_cover> <out_cover> # # {buffer_distance} # POLY # RIGHT


    Note:
    Buffer distance can be very small. As long as the clip polygon is within
    the hull, CREATETIN will interpolate an elevation.

  3. Use the CREATETIN command with the COVER subcommand to generate a TIN for features within the clip polgyon.

    Code:
    Arc: CREATETIN <out_tin>
    Arc: COVER <in_cover> POLY -9999 HARDCLIP


    Note:
    If all features in a coverage are z-less, you can use a {spot_value} of -9999 on the command line instead of using a {spot_item}.