Initiate processing (PROC)

The PROC command controls the processing and output of radar data.

PROC is a single-word command that specifies the type of processing to be performed, and the type of output to be generated.

The following table shows the modes available in the command word.PROC Modes
Mode	Description
Synchronous mode	The processor acquires, processes, and outputs one ray in response to each PROC command. Processing begins after each command is received.
Free running mode	A single PROC command is issued, and rays are continually output as fast as they can be produced and consumed. This continues until any other command is written, for example, a NOP can be used to terminate the free running mode with no other consequences.
Time Series mode	The processor acquires, processes, and outputs one ray of time series samples in response to each PROC command. Data are output as 8-bit time series, 16-bit time series, or 16-bit power spectra.

Optional dual-PRF velocity unfolding is chosen by command bits 8 and 9. For Doppler data either a 2:3, 3:4, or 4:5 PRF unfolding ratio may be selected. RVP10 performs the unfolding steps internally, so mean velocity is output with respect to the larger unambiguous interval. No additional velocity processing is needed except to change the velocity scale on any generated displays.

Spectral widths are scaled consistently with respect to the higher PRF, and require no user modification before being plotted.

When unfolding is selected, the internal trigger generator automatically switches rates on alternate rays. The switch over occurs immediately after the last pulse of the current ray has been acquired; thus overlapping the internal post-processing and output time, with transmitter stabilization and data acquisition at the new rate.

Output data are selected by the upper 6 bits of the PROC command. Packed archive output is selected by setting the ARC bit. Individual byte or word display output is selected by setting any or all of the Z, T, V, W, Zdr, and Kdp command word bits. When more than one of these bits is set, the output array consists of all of the bins for the leftmost selected parameter, followed by all of the bins for the next selected parameter, and so on. Bits selected in XARG #1 behave the same way, except that the output order is right-to-left. Both archive and display formats can be selected simultaneously, in which case the archive format is output first, followed by whichever individual display format values were also selected. The archive format is not recommended for use with new drivers, because it can only handle four of the many possible output parameter types.

In time series mode, there are three output data formats available. For backwards compatibility, there is an 8-bit integer format, in which the 8 most significant bits from the I, Q, and LOG signals are represented in a byte. This format is not recommended, because it generally misses weak signals. Vaisala recommends the floating-point format that uses 16-bits per A/D sample. There is also a 16-bit power spectrum output that is accurate to 0.01 dB (see also GPARM output word #10).

In addition to the above output data, the first words of each ray optionally contain additional information about the ray. These header words are configured by the CFGHDR opcode, and are included only if the NHD (No-Headers) bit in SOPRM Input #2 is clear.

For example, if TAG angle headers are requested, if the ARC, Z, and V bits are all set, and if there are 100 bins selected in the current range mask, then each RVP10 output ray consists of the following:


1]  TAG15  TAG0      \      From Start of Acquisition
2]  TAG31  TAG16     /      Interval
3]  TAG15  TAG0      \      From End of Acquisition
4]  TAG31  TAG16     /      Interval
*   200 words of packed archive data.
*   100 words of Corrected Reflectivity data in low byte only.
*   100 words of Velocity data in low byte only.

The Command word format for Synchronous Doppler Mode is:

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 ---------------------------------------------------------------
|   |   |   |   |    |   |   |   |   |   |   |   |   |   |   |   |
|ARC| Z | T | V | W  |ZDR| Unfold|KDP| 0   1 | 0   0   1   1   0 |  Command
|---|---|---|---|----|---|---|---|---|---|---|---|---|---|---|---|-

The Command word format for Free Running Doppler Mode is:

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 ---------------------------------------------------------------
|   |   |   |   |    |   |   |   |   |   |   |   |   |   |   |   |
|ARC| Z | T | V | W  |ZDR| Unfold|KDP| 1   0 | 0   0   1   1   0 |  Command
|---|---|---|---|----|---|---|---|---|---|---|---|---|---|---|---|

Either of these may be augmented by an optional XARG word. See Pass auxiliary arguments to opcodes (XARGS).

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 ---------------------------------------------------------------
|   |   |   |   |    |    |   |  Tx Vert  |  Tx Horz  |   |   |   |   
|                    |HCL |FLG|Phi Rho Ldr|Phi Rho Ldr|SQI|RHV|PDP|  XARG1
|---|---|---|---|----|----|---|---|---|---|---|---|---|---|---|---|

The Unfold parameter selects the dual-PRF unfolding scheme:

00 : No Unfolding    01 : Ratio of 2:3
10 : Ratio of 3:4    11: Ratio of 4:5

The ARC selects the archive output format in which four data bytes (see 8-Bit descriptions below) are packed in two output words per bin as follows:

 HighByte  Low Byte
--------------------
|        |         |
|   V    |    Z    |
|        |         |
-------------------- 

--------------------
|        |         |
|   W    |    T    |
|        |         |
--------------------

The remaining data parameters are available in both 8-Bit and 16-bit formats, according to SOPRM Command Input word #2 (see Setup operating parameters (SOPRM)). The same SOPRM word configures RVP10 for single or dual polarization. The latter is required for Kdp, PDP, and RHV to be computed properly.

PROC 8-bit and 16-bit Data Formats
Parameter	Description	8-bit Format	16-bit Format
V	Selects radial velocity data.	Mean velocity, expressed as a fraction of the unambiguous velocity interval, is computed from the unsigned byte `N` as: $V_{\frac{m}{\sec}} = V_{N y q u i s t} \times \frac{(N - 128)}{127.5}$ `0` Indicates velocity data is not available at this range `1` Maximum velocity towards the radar `128` Zero velocity `255` Maximum velocity away from the radar When velocity unfolding is selected, the output is still interpreted as above, except that the unambiguous interval is increased by factors of 2, 3, and 4 for 2:3, 3:4, and 4:5 unfolding.	Mean velocity in meters per second (m/s) is computed from the unsigned word `N` as: $V_{\frac{m}{\sec}} = \frac{(N - 32768)}{100}$ `0` Indicates velocity data is not available at this range `1` -327.67 m/s (towards the radar) `32768` 0.00 m/s `65534` +327.66 m/s (away from the radar) `65535` Reserved Code
W	Selects spectral width data.	Spectral width is computed from the unsigned byte `N` as: $W_{N y q u i s t} = \frac{N}{256}$ The overall range is a fraction between 1/256 to 255/256 of the unambiguous interval. The code of zero indicates that width data was not available at this range.	Spectral width in meters per second (m/s) is computed from the unsigned word `N` as: $W_{\frac{m}{\sec}} = \frac{N}{100}$ The overall range is from 0.01 m/s to 655.34 m/s in one cm/s steps as follows: `0` Indicates width data is not available at this range 1 : 0.01 m/s `65534` 655.34 m/s `65535` Reserved Code
Z	Selects clutter corrected reflectivity data.	The level in decibels is computed from the unsigned byte `N` as: $d B Z = \frac{(N - 64)}{2}$ The overall range is therefore from -31.5 dBZ to +95.5 dBZ in half-dB steps as follows: `0` Indicates no reflectivity data available at this range 1 : -31.5 dBZ `64` 0.0 dBZ `128` +32.0 dBZ `255` +95.5 dBZ	The level in decibels is computed from the unsigned word `N` as: $d B Z = \frac{(N - 32768)}{100}$ `0` Indicates no reflectivity data available at this range `1` -327.67 dBZ `32768` 0.00 dBZ `65534` +327.66 dBZ `65535` Reserved Code
T	Selects total reflectivity.	Same 8-bit and 16-bit coding formats as for clutter corrected reflectivity
ZDR	Selects differential reflectivity data.	The level in decibels is computed from the unsigned byte N as: $d B Z = \frac{(N 128)}{16}$ The overall range is from -7.935 dB to +7.935 dB in 1\16 dB steps as follows: `0` Indicates no reflectivity data available at this range `1` -7.9375 dB `128` 0.0000 dB `255` +7.9375 dB	Same as 16-bit decibel format for Z.
KDP	Selects dual polarization specific differential phase data.	Values are coded into an unsigned byte using a logarithmic scale. The KDP angles are multiplied by the wavelength in cm (to reduce dynamic range) and then converted to a log scale separately for both signs. The minimum value is 0.25 degcm/km. The maximum value is 150.0 degcm/km. A code of zero represents no data A code of 128 represents 0 deg*cm/km. The conversion equation for positive values (codes from 129 to 255) is: $K D P \times λ = 0.25 \times 600 [\frac{N - 129}{126}]$ The conversion equation for negative values (codes from 1 to 127) is: $K D P \times λ = - 0.25 \times 600 [\frac{127 - N}{126}]$	Same as 16-bit decibel format for Z, except that the units are hundredths of degrees per kilometer. No weighting by wavelength is introduced.
PDP	Selects dual polarization differential phase PDP data.	The phase angle in degrees is computed on a 180° interval from the unsigned byte `N` as: $ϕ D P (\mod 180) = 180 \frac{(N - 1)}{254}$ `0` Indicates no PDP data available at this range `1` 0.00° `254` 179.29° `255` Reserved Code	The phase angle in degrees is computed on a 360° interval from the unsigned word `N` as: $ϕ D P (\mod 360) = 360 \frac{(N - 1)}{65534}$ `0` Indicates no PDP data available at this range `1` 0.00° `65534` 359.995° `65535` Reserved Code
RHV	Selects dual polarization correlation coefficient RHV data.	The correlation coefficient is computed on the interval 0.0 ... 1.0 using a square root weighting of the unsigned byte `N` as: $P_{H V} = \sqrt{\frac{(N - 1)}{253}}$ `0` Indicates no RHV data available at this range `1` 0.0000 (dimensionless) `2` 0.0629 `253` 0.9980 `254` 1.0000 `255` Reserved Code	The correlation coefficient is computed on the interval 0.0 to 1.0 linearly from the unsigned word `N` as: $P_{H V} = \frac{(N - 1)}{65533}$ `0` Indicates no RHV data available at this range `1` 0.0 (dimensionless) `65534` 1.0 `65535` Reserved Code
SQI	Selects Signal Quality Index data.	This dimensionless parameter uses the same 8-bit and 16-bit data formats as RHV.
LDR	Selects Linear Depolarization Ratio, measured either on the horizontal receive channel while transmitting vertically, or on the vertical receive channel while transmitting horizontally.	The level in decibels is computed from the unsigned byte `N` as: `dB = -45.0 + (N-1) / 5` This spans an asymmetric interval around zero decibels, and allows for cross channel isolation as large as 45 dB. The range is from -45.0 ... dB in 0.2 dB steps as follows: `0` Indicates no LDR data available at this range `1` -45.0 dB `226` 0.0 dB `254` +5.6 dB `255` Reserved Code	Same as 16-bit decibel format for Z.
RHO	Selects Signal Quality Index data	This dimensionless parameter uses the same 8-bit and 16-bit data formats as RHV.
PHI	Selects the cross channel differential phase.	This parameter uses the same 8-bit and 16-bit angular data formats as PDP.
FLG	Selects flag word output.	Bits defined as follows: `0` Reflectivity obscured at this bin `1` Velocity obscured at this bin `2` Width obscured at this bin `3` Point clutter detected at this bin
HCLASS	Hydrometeor Classification (HydroClass) parameter.	There are several possible classification schemes. The choice is made in the hydroclass--band.conf file, where `` is `C` (for C-band and X-band radars) and `S` (for S-band radars). The legacy Meteo classifications (up to IRIS/RDA 8.12.6) are: `0` No measurement available `1` Non-meteorological target `2` Rain `3` Wet snow `4` Snow `5` Graupel `6` Hail Higher bits of the HCLASS data fields may contain results from further methods of classification. See `sig_data_types.h` and HCLASS data description in IRIS Programming Guide (M211318EN).
SNR	Signal-to-Noise ratio on the primary (horizontal) channel.	Uses the same storage format as Z.
Ta	Total power in the alternative polarization receive channel (usually vertical).	Uses the same storage format as T.
Za	Clutter corrected reflectivity in the alternative polarization receive channel (usually vertical). Uses the same storage format as Z. The command word format for time series mode is shown below.
TSOUT	Selects type of data to be output.	`00` 8-bit Time Series `01` Power Spectrum `10` 16-bit Time Series `11` Unused

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 ---------------------------------------------------------------
|   |   |   |   |   |    |       |   |   |   |   |   |   |   |   |
| TSOUT |     Sub Type   |Unfold |   | 1   1 | 0   0   1   1 |0  |  Command
|---|---|----------------|-------|---|-------|-------------------|

When the TSOUT bits select Power Spectrum then, depending on the current major mode, a further choice may be needed to select one of several spectral view points. The following table shows the values for the random phase major mode the possible values of Sub Type.

TSOUT Random Phase Major Mode Values
First Trip Value	First Trip Description	Second Trip Value	Second Trip Description
`0`	Raw First Trip	`4`	Raw Second Trip
`1`	Whitened First Trip	`5`	Whitened Second Trip
`2`	Cleaned First Trip	`6`	Cleaned Second Trip
`3`	Final First Trip	`7`	Final Second Trip

When the TSOUT bits select Time Series then, a further choice may be needed to select the time series from the first or second pulse when using the Hybrid Pulse Compression scheme. For the Random Phase major mode the possible values of Sub Type are:

0: Main pulse time series
1: Second pulse time series (if hybrid pulse)

When time series output is selected the output data consist either of (3xBxN) or (2xBxN) words, depending on the output format, where B is the number of bins in the current range mask and N is the number of pulses per ray. Data samples for each bin of pulse #1 are output first, followed by those for each bin of pulse #2, and so on up to pulse #N. The data are output in the same time-order that they were acquired.

In the floating point format, three words are used for each bin:

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 ---------------------------------------------------------------
|  |   |   |   |   |   |   |   |   |    |   |   |   |   |   |   |
|    Exponent      | S |              Mantissa                  |  (I)
|------------------|---|----------------------------------------|

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 ---------------------------------------------------------------
|  |   |   |   |   |   |   |   |   |    |   |   |   |   |   |   |
|    Exponent      | S |              Mantissa                  |  (Q)
|------------------|---|----------------------------------------|

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 ---------------------------------------------------------------
|  |   |   |   |   |   |   |   |   |    |   |   |   |   |   |   |
| 0  0   0   0 |              Log of Power in Sample            |  (LOG)
|--------------|------------------------------------------------|

To convert these legacy format floating I and Q samples to voltages:

Create a 12-bit signed integer in which bits 0 ... 9 are copied from the Mantissa field, and bits 10 and 11 are either 01 or 10 depending on whether S is 0 or 1.
Multiply this number by 2**(exponent-40), where the exponent field is interpreted as an unsigned 5-bit integer.
Multiply by the maximum voltage.

The resulting value has 12-bits of precision and a dynamic range of approximately 190 dB. The large dynamic range is necessary to cover the full range of data. In summary:

V o l t a g e = V_{M A X} \times (S i g n, M a n t i s s a) \times 2^{E x p o n e n t - 40}

The resulting voltage span is ± 4 × V_MAX. The extra factor of 4 is built into the format so that transient excursions above the full scale input voltage can be encoded properly.

A High-SNR packed floating format is also available that offers nearly the same dynamic range, but provides a 6 dB improvement in SNR, that is, a commensurate improvement in sub-clutter visibility of -78 dB versus -72 dB.

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 ---------------------------------------------------------------
|  |   |   |   |   |   |   |   |   |    |   |   |   |   |   |   |
|    Exponent      | S |              Mantissa                  |  High–SNR
|------------------|---|----------------------------------------|

The High-SNR packed format is similar to the legacy packed format except that it uses one extra mantissa bit and one fewer exponent bit. The dynamic range lost in the exponent is recovered through a formatting trick known as "soft underflow", that is, the mantissa is allowed to become unnormalized when the exponent is 0.

To decode this format when the exponent is non-zero, first create a 13-bit signed integer in which bits zero through ten are copied from the Mantissa field, and bits eleven and twelve are either 01 or 10 depending on whether S is 0 or 1. Then, multiply this by 2**(exponent-25), where the exponent field is interpreted as an unsigned 4-bit integer.

To decode the High-SNR format when the exponent is 0, interpret the mantissa as a 12-bit signed integer and multiply by 2**-24.

A complete analysis of the noise properties of the floating point codes would be fairly tricky. For the High-SNR format, the 12-bit mantissa with hidden normalization bit vary from 2048 ... 4095. The SNR therefore varies from 66 dB ... 72 dB and we can assign a mean value of 69 dB. Another 9 dB of useful range is contained within the code as follows:

In a floating point encoding format, the notion of fixed additive quantization noise is not really correct. For a signal having a given power, the additive noise within each instantaneous sample scales down according to the magnitude of that sample. The ensemble of noise terms thus contributes an RMS power that is smaller than the Peak-to-Noise ratio would imply. In the case of a sinusoidal input, this gives a 3 dB boost in effective SNR.
The format, of course, also represents negative amplitudes with the same relative precision as positive values. In a fixed-point format this would add 6 dB (one more bit) to the overall dynamic range and large-signal SNR. In the floating format we really only gain 3 dB (half a bit) because the RMS noises add independently on the positive and negative excursions.
The packed format is used to encode time series (I,Q) pairs, and it's the SNR properties of these pairs that we're really concerned about. To a first approximation, having a pair of values roughly doubles the information content and adds another 3dB to the SNR.

The last of the time series output words, the Log of Power in Sample, is provided for backwards compatibility. It can be calculated from the I and Q numbers. To convert to dBm it requires a slope and offset as follows:

d B m = P_{M A X} + S l o p e \times [V a l u e - 3584]

where:

P_MAX: +4.5 dBm for 12-bit IFDR, +6.0 dBm for 14-bit IFDR, +8.0 dBm for 16-bit IFDR
V_MAX: 0.5309 V for 12-bit IFDR, 0.6310 V for 14-bit IFDR, 0.7934 for 16-bit IFDR
Slope: Log Power Slope word 3 of the SOPRAM command. 0.03 is recommended.

For backwards compatibility, RVP10 produces a 8-bit fixed point time series format. Because of the limited dynamic range available, this only shows strong signals, and is not recommended for use. The I, Q, and Log power triplets are packed in two 16-bit output words as follows:


 HighByte    Low Byte
----------------------
|          |          |
| Q Sample | I Sample |  First Word
|          |          |
----------------------

----------------------
|          |          |
|   Zero   | Log Power|  Second Word
|          |          |
----------------------

The Log Power value is the upper 8 bits of the long format. The other numbers are produced by the equation:

V o l t a g e = V_{M A X} \times [\frac{S a m p l e}{128}]

When Power Spectrum output is selected, the spectrum size is chosen as the largest power of two (N2) that is less than or equal to the current sample size (N). When the sample size is not a power of two, a smaller spectrum is computed that by averaging the spectra from the first N2 and the last N2 points. The data format is one word/bin/pulse, in the same order as for time series output. Each word gives the spectral power in hundredths of dB, with 0 representing the level that would result from the strongest possible input signal (P_MAX). Thus, the spectral output terms are almost always negative.

The time series that are output by RVP10 are the filtered versions of the raw data, when available. If a non-zero time-domain clutter filter is selected at a bin, then the I and Q data for that bin show the effects of the filter. If you must observe the raw samples, make sure that no clutter filters are being applied.

In pulse pair time series mode with dual receivers, selecting (H+V) produces data in one of two formats according to the Sum H+V Time Series question in the Mp setup section:

Yes produces summed time series from both channels, but spectra from the DSP is the averaged spectra from each channel individually.

This allows the IRIS ascope utility to display either the spectrum-of-sum or sum-of-spectra according to whether the Spectra from DSP button is selected in the Processing/Gen-Setup window.
No produces the usual (BxN) time series output samples, except that the first half of these samples is the first half of the H data in their normal order. This is followed by a zero sample if (BxN) is odd; followed by the first half of the V data, also in their normal order.

Only the first halves of the individual H and V sample arrays are output by RVP10. As an example, if you select 25 bins and 100 pulses, then the output data consists of 1250 H samples (from all bins in the first 50 pulses), followed by 1250 V samples from the exact same set of bins and pulses. This is the more useful option when custom algorithms are being run on the data from the two separate receivers.

When the number of output words is large there is a possibility that the internal buffering within RVP10 may overflow and data may be lost. Due to internal memory limitations, the product (BxN) must be less than 12000. A bit in the latched status word indicates when time series overflows occur. In such cases, the correct number of words are still output, but they are all 0 after the point at which overflow was detected. See Get processor parameters (GPARM)