Feature Detection Output

Feature detection outputs a pandas dataframe with several variables. The variables, (with column names listed in the Variable Name column), are described below with units. Note that while these variables come initially from the feature detection step, segmentation and tracking also share some of these variables as keys (e.g., the feature acts as a universal key between each of these). See Tracking Output for the additional columns added by tracking.

Variables that are common to all feature detection files:

tobac Feature Detection Output Variables

Variable Name	Description	Units	Type
frame	Frame/time/file number; starts from 0 and increments by 1 to N times.	n/a	int64
idx	Feature number within that frame; starts at 1, increments by 1 to the number of features for each frame, and resets to 1 when the frame increments	n/a	int
hdim_1	First horizontal dimension in grid point space (typically, although not always, N/S or y space)	Number of grid points	float
hdim_2	Second horizontal dimension in grid point space (typically, although not always, E/W or x space)	Number of grid points	float
num	Number of grid points that are within the threshold of this feature	Number of grid points	int
threshold_value	Maximum threshold value reached by the feature	Units of the input feature	int
feature	Unique number of the feature; starts from 1 and increments by 1 to the number of features identified in all frames	n/a	int
time	Time of the feature	Date and time	object/python datetime
timestr	String representation of the feature time	YYYY-MM-DD HH:MM:SS	object/string
y	Grid point y location of the feature (see hdim_1 and hdim_2). Note that this is not necessarily an integer value depending on your selection of position_threshold	Number of grid points	float
x	Grid point x location of the feature (see also y)	Number of grid points	float
projection_y_coordinate	Y location of the feature in projection coordinates	Projection coordinates (usually m)	float
projection_x_coordinate	X location of the feature in projection coodinates	Projection coordinates (usually m)	float
lat	Latitude of the feature	Decimal degrees	float
lon	Longitude of the feature	Decimal degrees	float

Variables that are included when using 3D feature detection in addition to those above:

tobac 3D Feature Detection Output Variables

Variable Name	Description	Units	Type
vdim	vertical dimension in grid point space	Number of grid points	float64
z	grid point z location of the feature (see vdim). Note that this is not necessarily an integer value depending on your selection of position_threshold	Number of grid points	float64
altitude	z location of the feature above ground level	meters	float64

One can optionally get the bulk statistics of the data points belonging to each feature regiion or volume. This is done using the statistics parameter when calling :ufunc:`tobac.feature_detection_multithreshold` . The user-defined metrics are then added as columns to the output dataframe.