# calvdb — Dataset Sample

This folder contains a small sample of the full **calvdb** dataset, provided so that reviewers can inspect the data format without downloading the complete archive (6.02 GB).

## Contents

The sample includes Braasvellbreen glacier (RGI60-07.00025) taken from the **train split** of the benchmark.

## How the sample was created

Each Zarr store in this folder is taken directly from the full dataset without modification. The stores were copied from the full `zarr_zipped/` collection and are structurally identical to every other glacier store in calvdb.

## Zarr store structure

Each glacier is stored as a Zarr v3 group (zstd compression). Opening any store reveals the following arrays:

| Array | Shape | Description |
|---|---|---|
| `sdt` | `(T, H, W)` | Signed distance transform of the calving front; values clipped to ±2000 m |
| `imagery` | `(T, 5, H, W)` | Multispectral imagery: blue, green, red, NIR, SWIR-1 |
| `geophys` | `(T, 6, H, W)` | Geophysical channels: bed elevation, surface elevation, ice thickness, surface velocity, strain rate, ice–fjord mask |
| `climate` | `(T, 2)` | Climate forcing: surface runoff, ocean temperature |
| `trace` | `(T, H, W)` | Rasterised calving-front line (used for evaluation only, not a model input) |
| `dates` | `(T,)` | Observation dates in YYYY-MM-DD format |
| `valid_sdt` | `(T,)` | Boolean mask — True if the SDT observation is valid |
| `valid_img` | `(T,)` | Boolean mask — True if the imagery observation is valid |
| `valid_clm` | `(T,)` | Boolean mask — True if the climate observation is valid |
| `valid_trace` | `(T,)` | Boolean mask — True if the trace observation is valid |
| `sensors` | `(T,)` | Sensor identifier for each imagery observation |

All arrays share the same time axis `T`. Spatial dimensions `H × W` vary per glacier. Spatial resolution is 30 m; CRS is EPSG:3995 (Arctic Polar Stereographic). 

> **Note on `ice_fjord_mask` (geophys channel 5):** Although `ice_fjord_mask` is stored in the zarr archive as geophysical channel 5 for completeness, it is excluded from the model input tensor in the baseline experiments due to inaccuracies in the mask boundary for several glaciers. It is retained in the dataset to support future work that may use or improve upon this variable.

## Further details

- **Full dataset, splits and normalization:** see the main [README](../README.md)