added answer to question for readers

Author: michaeldorman

05-raster-vector.qmd

@@ -92,11 +92,13 @@ out_image_mask, out_transform_mask = rasterio.mask.mask(
 ```
 
 Note that we need to choose and specify a 'No Data' value, within the valid range according to the data type.
-Since `srtm.tif` is of type `uint16` (how can we check?), we choose `9999` (a positive integer that is guaranteed not to occur in the raster).
+Since `srtm.tif` is of type `uint16` (how can we check?[^answer_srtm_dtype]), we choose `9999` (a positive integer that is guaranteed not to occur in the raster).
 Also note that **rasterio** does not directly support **geopandas** data structures, so we need to pass a 'collection' of **shapely** geometries: a `GeoSeries` (see above) or a `list` of **shapely** geometries (see next example) both work.
 The output consists of two objects.
 The first one is the `out_image` array with the masked values.
 
+[^answer_srtm_dtype]: The answer is `src_srtm.meta['dtype']`, which returns `'uint16'`.
+
 ```{python}
 out_image_mask
 ```