7-7. Add a combined constraint

The principle

A combined constraint takes a continuous variable and groups it into named bands — effectively making categories out of continuous data. The viewer renders it as checkboxes rather than a slider, which is easier to use when the meaningful divisions are known in advance: altitudinal zones, aspect classes, uncertainty bands, or flood return periods.

We will add a second constraint on the same elevation COG used in 7-5, this time as altitudinal zones.

Configure it

1. Add constraint → Direct URL → paste the DSM again:

   https://eox-gtif-public.s3.eu-central-1.amazonaws.com/DHI/Copernicus_DSM_COG_10m_3857_fix.tif
   

2. Set:

   • Label — Altitudinal zones
   • Interactive — on
   • Constraint Type — Named ranges (continuous with labelled ranges)
   • Units — meters

3. Add four named ranges:

   Label	Min	Max
   0 to 1000	0	1000
   1001 to 2000	1001	2000
   2001 to 3000	2001	3000
   > 3000	3001	4000

   Bulk Add

   Rather than typing each range, select Bulk Add. Give a prefix, the number of ranges and the overall from/to values, check the preview, and the ranges are generated for you. Edit the labels afterwards if you want wording like "> 3000".

4. Save the constraint.

   Note

   Populate from COG is not available for combined constraints — the band boundaries are a design decision, not something that can be read from the file.

View the result

In the Preview the layer now has both an Elevation slider and a set of Altitudinal zones checkboxes. Untick 2001 to 3000 and > 3000 to remove the high alpine zones in one click, rather than dragging a slider handle to an approximate position.

Two constraints, one source

Because both constraints read the same DSM they interact. If the Elevation slider is set to 0–1000 and only the 2001 to 3000 zone is ticked, nothing will render at all — there are no pixels that satisfy both.

Did you remember to export?