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Constraints

The Constraints section of a layer card defines additional raster masks that limit where a layer is rendered, based on threshold values pulled from another COG. A typical example: only show a vegetation index where elevation is below 2000 m, or where a land-cover class equals "forest".

Layer Card Controls row showing the Constraint Slider toggle

When to use

  • Hide pixels outside a numeric range (continuous constraint).
  • Show only specific class values (categorical constraint).
  • Combine ranges with named labels for a UI slider (combined constraint).

If the user does not need to mask the layer interactively, leave Constraints empty.

Configure

Expand Constraints in the layer card and add one or more entries. Each ConstraintSourceItem has:

  • URL — the constraint COG.
  • Format — cog (only COG is supported).
  • Label — display name shown in the viewer's constraint UI.
  • Type — one of:
    • continuous — numeric range with min, max, optional units.
    • categorical — discrete values listed in constrainTo as { label, value }.
    • combined — named ranges in constrainTo as { label, min, max }.
  • Interactive — when true, the viewer exposes a slider/picker so the user can change the constraint at runtime. When false, the constraint is fixed.
  • Band index — optional, defaults to band 1.

To expose the slider control set layout.layerCard.controls.constraintSlider: true.

Validation

  • url, format, label, and type are required.
  • For continuous, both min and max should be set so the slider has a defined range.
  • For categorical, constrainTo entries need value; for combined they need min/max.
  • The constraint COG should align spatially with the displayed layer; misalignment causes apparent dropouts.