wiki:cookbook/QIT
Last modified 5 years ago Last modified on 03/04/13 14:40:32

1. Algorithm name

Total quality index for scans/volumes – QI_TOTAL

2. Basic description

a) Physical basis of the algorithm

Integration of quality indices generated by all or selected quality algorithms.

b) Amount of validation performed so far

Not developed yet.

c) References (names and contact information of all developers during the evolutionary history, scientific papers)

IMGW, Department of Ground Based Remote Sensing.

3. ODIM metadata requirements for I/O

  • General “what”: source(NOD).
  • Dataset-specific “what” for QI data: gain, offset, nodata, undetect.
  • Dataset-specific “where” for QI data: nbins, nrays.

4. Input data

a) What kind of radar data (including the list of previous algorithms and quality flags applied)

object=PVOL or SCAN; quantity=QIND (QI information generated by particular quality algorithms).

b) Other data (optional and mandatory, applying “universally” agreed formats, geometry)

None.

5. Logical steps, using any of: text, flow charts, graphics, equations (or references to equations), conditional branches in “all possible cases”.

Quality Index (QI) definition

Quality index QI is a unitless quantity with values in the range from 0 to 1, where: QI = 0 for bad data, QI = 1 for excellent data.

Algorithm parameters

Set of the algorithm parameters:

Description Denotation Available options Default value
List of QI fields QIFields Example: “pl.imgw.radvoqc.att, pl.imgw.radvolqc.spike”;
NULL means all available QI fields
NULL (all available)
Methods of combination of particular QIs into total QI Method multi / add / min multi
Overwrite if total QI already exists Overwrite 0 (no) / 1 (yes) 0

At first the XML file is checked whether there exists group for a considered radar (based on the radar name read from "what"/source(NOD)), which contains the algorithm parameters. If "yes", then parameters are read from that XML group, but if it is impossible for a particular parameter, then default value from source code is taken. If the group does not exist, parameters are read from <default> group in XML file in analogous way.

If the algorithm is run by means of BALTRAD toolbox then all the algorirthm parameters for each specific radar should be placed in relevant XML file by the BALTRAD system admin. Default parameters are placed in the file by admin as well. Moreover, the algorithm default parameters are also included in software.

Computation

Total quality index is generated from all or selected quality indices earlier generated by BALTRAD quality algorithms. It constitutes the final stage in data volumes processing.

The total QI is generated:

  • from all QI fields available in qualityn fields (quantity=QIND),
  • from QI fields selected for particular quality algorithms ("how": task).

If there are no available particular QI fields then total QI is not generated. If a given pixel is marked as "nodata" value at least in one of QI fields then "nodata" is assigned to total QI as well.

The following methods for the QIs combination are to select:

  • multi (multiplicative) $ QI = \Pi_{i=1}^{n}QI_{i} $
  • add (additive) $ QI = \frac{1}{n} \sum_{i=1}^{n}QI_{i}    $
  • min (minimum value) $ QI = \text{min}(QI_{i})    $

where i = 1, …, n; n is the number of particular quality indices.

6. Output

a) Data type using ODIM notation where possible, e.g. DBZH

No changes.

b) Quality index (QI) field

Total quality index QI with:

  • "pl.imgw.qi_total" in quality-specific "how": task,
  • combination method and the particular contributing QIs listed in "how": task_args.

7. Outline of a test concept exemplifying the algorithm, as a suggestion for checking that an implementation has been successful.

TBD