Please don't rely on these maps, or any map, to decide whether the terrain is steep enough to avalanche! And remember to pay attention not only to the terrain you are on but also to the terrain that is above and connected to your terrain.
The fifth edition of the Wasatch Backcountry Skiing Map is based on high-resolution LIDAR elevation data that was measured from aircraft. This data was then resampled to make it more practical for backcountry travelers.
The contour lines are based on 0.5 meter (20 inch) and 2 meter (6 foot) LIDAR data. This data was then resampled over 5 meters (16 feet).
The relief (aka "terrain") shading uses 0.5 and 2 meter LIDAR data.
The 30° slope shading was based on 0.5 and 2 meter high-resolution data that was resampled over 10 meters (33 feet). This was done so the edges of large boulders that are on flat terrain don't appear as steeper than 30 degrees. No smoothing or feathering was performed on the slope shading.
You can use the Avalanche Slope Ruler to measure the slope on printed maps. Keep in mind that the ruler's accuracy is only as good as the map's underlying data (and your eyesight).
You can use the avalanche inclinometer to measure slope angles using your phone when in the field.
