(quick-start)=

# Quick start

## Sample data

xDEM comes with some sample data that is used throughout this documentation to demonstrate the features. If not done already, the sample data can be downloaded with the command

```python
xdem.examples.download_longyearbyen_examples()
```

The dataset keys and paths can be found from

```python
xdem.examples.available
```

## Load DEMs and calculate elevation difference

```python
import xdem

# Load data
dem_2009 = xdem.DEM(xdem.examples.get_path("longyearbyen_ref_dem"))
dem_1990 = xdem.DEM(xdem.examples.get_path("longyearbyen_tba_dem_coreg"))

# Calculate the difference
ddem = dem_2009 - dem_1990

# Plot
ddem.show(cmap='coolwarm_r', vmin=-20, vmax=20, cb_title="Elevation change (m)")

# Save to file
ddem.save("temp.tif")
```

A detailed example on how to load raster data, reproject it to a different grid/projection, run simple arithmetic operations such as subtraction, plotting the data and saving to file can be found in the example gallery {ref}`sphx_glr_basic_examples_plot_dem_subtraction.py`.

% .. raw:: html
%
%     <div class="sphx-glr-thumbcontainer" tooltip="DEM subtraction">
%
% .. only:: html
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%  .. figure:: /auto_examples/images/thumb/sphx_glr_plot_dem_subtraction_thumb.png
%      :alt: DEM subtraction
%
%      :ref:`sphx_glr_auto_examples_plot_dem_subtraction.py`