Navigate time, depth, and files
Goal: move through the fourth dimension efficiently — animate time, seek vertical levels, and switch between open datasets.
Step and play the time axis
| Task | Do this |
|---|---|
| Previous / next time slice | ← / → or < / > |
| Play / pause the timeline | Space, or click the Play/Pause button |
| Playback speed | - / + or the labeled speed controls on the timeline |
| Seek to a date | click or drag the timeline gauge |
| Switch active file | { / } (the header shows “opened file N/M”) |
When several files form one collection, the timeline spans all of them and file switching keeps you on the corresponding time slot of the new file.
Seek vertical levels
For variables with a depth/level axis, a full-width Level bar sits above
the time bar showing index/N plus the CF level label (falling back to the
dimension name when the file has none):
- Click or drag the level bar to seek.
- Scroll over it to step one level.
[/]step levels from anywhere.Tabfocuses the sidebar Level list;↑/↓move the cursor,Enterapplies it,Tab/Escleave focus.
Two-dimensional variables hide the level bar entirely — no dead controls.
Zoom to a region
Drag across the map to zoom to a rectangle. To enter numeric bounds, open the
command palette with Ctrl-P or :, search for Set view bounds, and enter
minimum and maximum x/y values. Tab moves between fields; Enter applies;
Esc cancels. The existing box zoom and pan controls remain available.
For geographic axes, longitude accepts signed degrees or 0..360, and
latitude must be within -90..90. The viewer maps coordinate endpoints to the
smallest source-index range containing the samples. Other axes use their
one-dimensional coordinate values when available, or inclusive zero-based
indices when they are dimension-only. Invalid or non-overlapping bounds leave
the accepted view unchanged. Curvilinear grids use a row/column envelope and
disclose that approximation in the status line.
Selecting a different variable returns to that variable’s global view, since its coordinate system and domain may differ. The zoom for a dataset is still remembered between launches; explicit CLI bounds override the restored zoom. See the CLI reference for startup examples.
Session restore
ncv remembers your last view (variable, slice, limits) per dataset and
restores it on the next launch. To start clean:
ncv --no-restore data.nc
The session directory can be relocated with NCVIEW_SESSION_DIR (useful on
shared HPC head nodes). See Environment reference.