Description of the available data

experimental_results.csv
This file contains the results from the experiments conducted with artificial snowflakes. The snowflakes were produced by additive manufacturing and the drag is measured in a water-glycerol mixture. 
The file includes both three-dimensional geometric descriptors as well as two-dimensional geometric descriptors of the projections. The header contains additional information like the selected reference area or the camera perspective. 

snowflake_projections.csv
This file contains the data set of projections of the artificial snowflakes. Every ID refers to a three-dimensional snowflake model. For each snowflake 100 projections are generated. Three-dimensional descriptors are independent of the particle orientation and thus do not change for a single snowflake. Note that the quantities here are at their original scale and have not been scaled up like the three-dimensional models. 
The specified volume must be used with caution. Obtaining the snowflake mass from the volume and the density of ice is prone to error since the thickness of the ice structures has a significant influence on the volume. On the small scale structures of the models this accuracy cannot be guaranteed. 
The major and minor axes refer to an ellipse with the same normalized second central moments as the projection. 
The orientation is specified in terms of the rotation around each axis that was performed to yield the projection. The three-dimensional models were first rotated around the x-axis, subsequently around the y-axis and finally around the z-axis. 
The filename of the image depicting the projection and the resolution of these images are noted in the last columns of the table. 

snowflake_3D_models.zip
This archive contains the STL files describing the three-dimensional models of the snowflakes. In comparison to the natural equivalents, the have been scaled up by a factor of five. 
The algorithm for generating the snowflakes is described in the following publication:
Leinonen J, Moisseev D, Nousiainen T (2013) Linking snowflake microstructure to multi-frequency radar observations. Journal of Geophysical Research: Atmospheres 118(8):3259–3270, 10.1002/jgrd.50163

snowflake_projections.zip
This archive contains the projections of the snowflakes. The CSV file resolutions.csv again specifies the resolutions of the images in m/px.