SCC Documentation: comparison docs/depolarization/depolarization.rst

-:07924e0a9911
+:270ab1db32db
 1. Particle Linear Depolarization Ratio Implementation
 ======================================================
 The most important improvement included in the SCC v4.0 is the implementation of a new optical product which is the particle linear depolarization ratio.
+.. important::
+If your lidar system is not equipped with any polarization channels **NO** changes are required. In this case, the SCC v4.0 should work using the same input files and the same database configurations you have used with the SCC v3.11. Anyway as in the SCC v4.0 several bugs have been fixed, it is recommended to re-run all the measurement IDs you have submitted. For doing that you just need to reprocess all your data without the need to submit raw data files already uploaded on the server.
 1.1 Background
 --------------
 The calculation of the volume linear depolarization ratio profile (*VLDR*) and particle linear depolarization ratio profile (*PLDR*) needs two different steps:
 #. the calibration of the polarization sensitive lidar channels;
 #. the calculation of the *VLDR* or *PLDR* itself.
-The SCC allows the user to make both the above points. In particular the calibration step is made by a completely new module called **scc\_calibrator** which computes the *apparent calibration factor* :math:`\beta^*` out of the pre-processed data provided by the standard **ELPP** (Earlinet Lidar Pre-Processor) module and it records it in the SCC database (SCC\_DB). Once logged into the SCC\_DB this factor can be used whenever it is necessary.
+The SCC allows the user to make both the above points. In particular the calibration step is made by a completely new module called **ELDEC** (Earlinet Lidar Depolarization Calibrator) which computes the *apparent calibration factor* :math:`\eta^*` out of the pre-processed data provided by the standard **ELPP** (Earlinet Lidar Pre-Processor) module and it records it in the SCC database (SCC_DB). Once logged into the SCC_DB this factor can be used whenever it is necessary.
 The raw lidar calibration measurements should be put in a NetCDF file which has the same structure as the “standard” raw SCC NetCDF input file (for more details see sections 2 and 3.2).
 New signal types have been introduced to take into account special channel configurations used for calibration purposes.
 Moreover new product types for both calibration and *PLDR* calculation have been defined. As, in principle, it is possible to calculate the *PLDR* only when the aerosol backscatter coefficient profile is available the following new products have been defined:
-#. *Linear polarization calibration (factor* h) *(product\_type\_id=6);*
+#. *Linear polarization calibration (factor* :math:`\eta`) *(product_type_id=6);*
 #. *Raman backscatter and linear depolarization ratio
-(product\_type\_id=7);*
+(product_type_id=7);*
 #. *Elastic backscatter and linear depolarization ratio
-(product\_type\_id=8).*
+(product_type_id=8).*
 The first product in the above list is used only for calibration while the other two are used for the calculation of *PLDR*. Basically, in most of the cases, the products 2 and 3 are equivalent to the corresponding backscatter product types with the exception that also the following new variables are available:
 ::
 double VolumeDepol(Length) ;
 double ErrorVolumeDepol(Length) ;
-ErrorVolumeDepol:long\_name = "absolute error of VolumeDepol" ;
+ErrorVolumeDepol:long_name = "absolute error of VolumeDepol" ;
 double ParticleDepol(Length) ;
 double ErrorParticleDepol(Length) ;
-ErrorParticleDepol:long\_name = "absolute error of ParticleDepol" ;
+ErrorParticleDepol:long_name = "absolute error of ParticleDepol" ;
 1.2 Polarization calibration
 ----------------------------
 An important point is the definition of reliable *PLDR* calibration procedures. Within EARLINET the following calibration procedures are currently used:
 a) Rayleigh calibration;
-b) +45 calibration method, or D90 calibration method (made by +45 and -45 measurements);
+b) +45 calibration method, or :math:`\Delta90` calibration method (made by +45 and -45 measurements);
 c) 3 signals (total, cross and parallel).
 It is well known that method a) could produce easily large errors on *PLDR* which cannot be controlled. For this reason only the methods b) and c) can be used to provide reliable polarization calibrations and so only those methods will be implemented in the SCC.
 For what it concerns the method c) it, basically, requires to solve the equation:
 1.3 SCC procedure to calculate the PLDRP
 ----------------------------------------
 According to what mentioned before the SCC calculates the *PLDR* through the following steps:
-#. The user needs to create a new system configuration in the SCC\_DB    including only lidar channels used for the calibration. One (or more) *Linear polarization calibration (product\_type\_id=6)* product should be associated to this new configuration (see section 3.2 for more details);
+#. The user needs to create a new system configuration in the SCC_DB    including only lidar channels used for the calibration. One (or more) *Linear polarization calibration (product_type_id=6)* product should be associated to this new configuration (see section 3.2 for more details);
 #. This new system configuration should contain only the polarization channels in the configuration used for the calibration (for example rotated in the polarization plane of +45 degrees). A channel in calibration measurement configuration should have a **DIFFERENT** channel ID from the channel ID corresponding to the same channel in standard measurement configuration. For example, if a system has two polarization channels which in standard measurement configuration correspond to the channel ID=1 and 2 respectively, the same physical channels under calibration measurement configuration should correspond to different channel IDs (let's say ID=3 and 4 for the +45 degrees polarization rotated channels and ID=5 and 6 for the -45 degrees polarization rotated ones in case D90 calibration method is used). Moreover, the polarization channels should be labeled correctly using the new signal types available (*+45elPT, +45elPR, -45elPT, -45elPR, +45elPTnr, +45elPTfr, +45elPRnr, +45elPRfr, -45elPTnr, -45elPTfr, -45elPRnr, -45elPRfr).* For more details see section 3.2;
 #. In SCC v4.0 the polarization channels are **NOT** labeled on the base of their polarization state (as it was done in the SCC v3.11) but **ALWAYS** as transmitted and reflected channels. So the channels that in SCC v3.11 were labeled as *elCP, elCPnr, elCPfr, elPP, elPPnr elPPfr* will be labeled in SCC v4.0 as *elPR, elPRnr elPRfr elPT, elPTnr elPTfr* where the letter *T* stands from transmitted and the letter *R* for reflected.
 *elCPfr→ elPTfr*
 Please be sure these modifications reflect to your actual lidar setup(cross channels are transmitted and parallel channels are reflected);
 4. The user needs to submit a file (same format as raw SCC input file) containing the raw data for the lidar channels defined at the point 1 (see section 3.2 for more details);
-#. The file at point 2 is pre-processed by **ELPP** module which applies the standard pre-processing procedures applied to “standard” lidar data;
+#. The file at point 4 is pre-processed by **ELPP** module which applies the standard pre-processing procedures applied to “standard” lidar data;
-#. The pre-processed files are then processed by the new modules **scc\_calibrator** which calculates :math:`\eta^*` *the apparent calibration factor* and logs it into the SCC\_DB;
+#. The pre-processed files are then processed by the new modules **ELDEC** which calculates :math:`\eta^*` *the apparent calibration factor* and logs it into the SCC_DB;
-#. The user needs to create a new system configuration in the SCC\_DB (which should be different from the one used for the calibration) and associate it the new product *Raman backscatter and linear depolarization ratio product\_type\_id=7)* or *Elastic backscatter and linear depolarization ratio (product\_type\_id=8).* Alternatively the calculation of those products can be added to an already existing lidar configuration as long as it is different from the calibration one;
+#. The user needs to create a new system configuration in the SCC_DB (which should be different from the one used for the calibration) and associate it the new product *Raman backscatter and linear depolarization ratio product_type_id=7)* or *Elastic backscatter and linear depolarization ratio (product_type_id=8).* Alternatively the calculation of those products can be added to an already existing lidar configuration as long as it is different from the calibration one;
-#. The product defined at point 5 should be linked to the product containing the polarization calibration (defined at point 1) in a way that the *apparent calibration factor* can be selected from the SCC\_DB (see section 3.3 and in particular figure 3.4);
+#. The product defined at point 7 should be linked to the product containing the polarization calibration (defined at point 1) in a way that the *apparent calibration factor* can be selected from the SCC_DB (see section 3.3 and in particular figure 3.4);
 #. The user needs to submit another SCC raw data file containing the “standard” measurements;
-#. Finally **ELPP** and **ELDA** will produce a b-file containing backscatter coefficient profile and *PLDR*. In particular this calculation is made in two different steps: from the pre-processed lidar polarization signals, and taking into account the *apparent calibration factor* and the *calibration factor correction K* (defined as option of *Linear polarization calibration* product\ *)* written into the SCC\_DB, an “apparent” *VLDR* :math:`\delta^*` is calculated. Even if :math:`\delta^*` is a calibrated quantity it can be still affected by possible systematic errors due to not perfect optics or alignment of the system;
+#. Finally **ELPP** and **ELDA** will produce a b-file containing backscatter coefficient profile and *PLDR*. In particular this calculation is made in two different steps: from the pre-processed lidar polarization signals, and taking into account the *apparent calibration factor* and the *calibration factor correction K* (defined as option of *Linear polarization calibration* product\ *)* written into the SCC_DB, an “apparent” *VLDR* :math:`\delta^*` is calculated. Even if :math:`\delta^*` is a calibrated quantity it can be still affected by possible systematic errors due to not perfect optics or alignment of the system;
-#. To take into account these errors a corrected *VLDR* (:math:`\delta`) is calculated using the *polarization cross-talk correction parameters* *G* and *H* calculated on the base of Müller matrix formalism. These cross-talk correction parameters (*G* and *H*) are stored in the SCC\_DB for each lidar channels (see section 3.1 in particular figure 3.2). Finally the *PLDR* is calculated using the backscatter coefficient profile and the molecular LDRP calculated by ELPP considering the center wavelength and bandwidth of the channels interference filter.
+#. To take into account these errors a corrected *VLDR* (:math:`\delta`) is calculated using the *polarization cross-talk correction parameters* *G* and *H* calculated on the base of Müller matrix formalism. These cross-talk correction parameters (*G* and *H*) are stored in the SCC_DB for each lidar channels (see section 3.1 in particular figure 3.2). Finally the *PLDR* is calculated using the backscatter coefficient profile and the molecular LDRP calculated by ELPP considering the center wavelength and bandwidth of the channels interference filter.
-The *apparent calibration factor* :math:`\eta^*` is calculated by the **scc\_calibrator** module as the geometrical mean of the ratio of the +/-45 degrees reflected to the +/- 45 degrees transmitted signals within an altitude calibration range defined by the users in the raw data input files.
+The *apparent calibration factor* :math:`\eta^*` is calculated by the **ELDEC** module as the geometrical mean of the ratio of the +/-45 degrees reflected to the +/- 45 degrees transmitted signals within an altitude calibration range defined by the users in the raw data input files.
 In case of +45 calibration method :math:`\eta^*` is calculated by:
 .. math::
 \eta^* = \frac{I_R}{I_T}(+45)
-While in case of D90 calibration method:
+While in case of :math:`\Delta90` calibration method:
 .. math::
 \eta^* = \sqrt{\frac{I_R}{I_T}(+45) \frac{I_R}{I_T}(-45)}
 **ELDA** module calculates the “apparent” *VLDR*:
 .. math::
 \delta_{\alpha} = \frac{(1 + \delta_m)\delta R - (1 + \delta)\delta_m}{(1 + \delta_m)R - (1 + \delta)}
 where:
-- :math:`\eta^*` is the *apparent calibration factor* calculated by **scc\_calibrator**
+- :math:`\eta^*` is the *apparent calibration factor* calculated by **ELDEC**
 - *K* is the *calibration factor correction* defined as polarization product option
 - :math:`I_T` and :math:`I_R` are the transmitted and the reflected signals in the polarization detection set-up
-- :math:`G_{T,R}` and :math:`H_{T,R}` are *polarization cross-talk correction parameters* for the transmitted and reflected signals used to correct for systematic errors. Both these factors are defined in the SCC\_DB for each lidar channel.
+- :math:`G_{T,R}` and :math:`H_{T,R}` are *polarization cross-talk correction parameters* for the transmitted and reflected signals used to correct for systematic errors. Both these factors are defined in the SCC_DB for each lidar channel.
 - :math:`\delta_m` is the molecular linear depolarization ratio calculated by ELPP
 - *R* is the backscatter ratio
 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
 | total                | 1                           | 0               | 1               | 0               |
 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
 | parallel             | 1                           | 1               | 1               | -1              |
 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
-| cross                | 1                           | -1              | 1               | +1              |
+| cross                | 1                           | -1              | 1               | 1               |
 +----------------------+-----------------------------+-----------------+-----------------+-----------------+
 The *apparent calibration factor* (:math:`\eta^*`), *the calibration factor correction* (*K*) and the *polarization cross-talk correction parameters* are stored by **ELPP** module in the intermediate NetCDF files using the following variables:
 - :code:`Polarization_Channel_Gain_Factor` (*apparent calibration factor* - :math:`\eta^*` )
 2. Changes of the SCC input format
 ==================================
 The following minor changes have been applied to raw SCC data format:
-#. The optional variable *ID\_Range* has been **REMOVED**;
+#. The optional variable *ID_Range* has been **REMOVED**;
-#. The **OPTIONAL** variable :code:`int Signal\_Type(channels)` has been added. The possible values are the same available in the SCC\_DB:
+#. The **OPTIONAL** variable :code:`int Signal_Type(channels)` has been added. The possible values are the same available in the SCC_DB:
 :code:`0` :math:`\rightarrow` :code:`elT`
 :code:`1` :math:`\rightarrow` :code:`elTnr`
 3. The variables:
 ::
-double Pol\_Calib\_Range\_Min(channels)
+double Pol_Calib_Range_Min(channels)
-double Pol\_Calib\_Range\_Max(channels)
+double Pol_Calib_Range_Max(channels)
 have been added. Both these variable are **MANDATORY** for any calibration raw dataset. These variable should be included only the polarization calibration measurements and should specify the altitude range (meters) in which the polarization calibration should be made. For more details see section 3.3;
 4. The variable :code:`Depolarization_Factor` has been **REMOVED**.
 .. warning:: After this transition period **ONLY** automatic calibration will be allowed!
 5. The new **OPTIONAL** variable:
-:code:`string channel\_string\_ID(channels)`
+:code:`string channel_string_ID(channels)`
 has been introduced.
 Starting from SCC v4.0 the lidar channel can be identified not only by using integers (as it happened until SCC v3.11) but also by using strings.
 This section describes all the practical steps the users need to follow to switch from SCC v3.11 to new SCC v4.0.
 :IMPORTANT:
 If your lidar system is not equipped with any polarization channels **NO** changes are required. In this case, the SCC v4.0 should work using the same input files and the same database configurations you have used with the SCC v3.11. Anyway as in the SCC v4.0 several bugs have been fixed,it is recommended to re-run all the measurement IDs you have submitted. For doing that you just need to reprocess all your data without the need to submit raw data files already uploaded on the server.
-The practical example reported below describes the modifications required to use the SCC v4.0 for lidar systems equipped with polarization channels.
+The practical example reported below describes the modifications required to use the SCC v4.0 for lidar systems equipped with polarization channels. Lidar systems not equipped with polarization channels do not require any modification to switch to SCC v4.0.
 3.1 Modification of polarization channel parameters
 ---------------------------------------------------
 In what it follows it is assumed you already have registered one or more lidar configurations in the SCC database and that such configurations have been already used to produce optical products (aerosol extinction and/or backscatter coefficients) by means of the SCC v3.11.
 3.2 Definition of new calibration configuration and product
 -----------------------------------------------------------
 In this section we will see how to set the polarization calibration parameters: the calibration constant (called :math:`\eta^*` in section 1.3) and the correction to calibration constant (called K in section 1.3). In order to provide such parameters you need to define a new system configuration to be used **ONLY** for calibration purposes. Such new configuration should include the polarization channels in the measurement configuration used for the calibration. Let's suppose we want to use the :math:`\Delta90` calibration method.
-In this case we need to define a new configuration (called for example “depol_calibration”) as reported in the table 3.3. As you can see the configuration “depol\_calibration” includes 4 “new” channels. Actually the channels “532 cross +45 degrees” (channel ID=10) and “532 cross -45 degrees” (channel ID=12) refer to the same physical channel “532 cross” reported with channel ID=3 in table 3.2. Anyway we need to define two new channel IDs to identify the “532 cross” channel in the two polarization rotated configurations (+45 and -45 degrees) needed to apply the D90 calibration method. The same is true for the “532 parallel” channel. The polarization rotated channels should be labeled with the corresponding signal type as reported in table 3.3 (see figure
+In this case we need to define a new configuration (called for example “depol_calibration”) as reported in the table 3.3. As you can see the configuration “depol_calibration” includes 4 “new” channels. Actually the channels “532 cross +45 degrees” (channel ID=10) and “532 cross -45 degrees” (channel ID=12) refer to the same physical channel “532 cross” reported with channel ID=3 in table 3.2. Anyway we need to define two new channel IDs to identify the “532 cross” channel in the two polarization rotated configurations (+45 and -45 degrees) needed to apply the D90 calibration method. The same is true for the “532 parallel” channel. The polarization rotated channels should be labeled with the corresponding signal type as reported in table 3.3 (see figure
 3.1).
-**Table 3.3:** Polarization calibration configurations assuming D90
+**Table 3.3:** Polarization calibration configurations assuming :math:`\Delta90` calibration method
-calibration method
 +----------------------------+--------------+----------------+----------------------+
 | Channel Name               | Channel ID   | Channel Type   | depol_calibration    |
 +----------------------------+--------------+----------------+----------------------+
 | 532 cross +45 degrees      | 10           | +45elPT        | x                    |
 **Figure 3.3:** Options for *Linear polarization calibration product*.
 As you can see it is possible to fill in only the K correction factor and not the calibration constant :math:`\eta^*`.
-Actually for a **LIMITED** period of time it will be possible to fill in also the constant :math:`\eta^*` using a temporary tab called *Polarization calibration constant*. This has been done to provide the users with the possibility to continue to use the SCC even if an automatic calibration made by the SCC was not submitted yet. Anyway after a transition period it will be **NOT** possible to provide calibration constant using this procedure and the parameter :math:`\eta^*` can be calculated **ONLY** by the SCC as result of the submission of a proper calibration raw input dataset. The format of this input file is the same as the standard SCC input file. The only difference is that is should contain calibration measurements instead of standard measurements. Following our example, such file should contain the measurement performed at +45 and -45 degrees at 532nm. Also the channel IDs in the file should reflect the ones reported in table 3.3.
+Actually for a **LIMITED** period of time it will be possible to fill in also the constant :math:`\eta^*` using a temporary option shown in figure 3.4. This has been done to provide the users with the possibility to continue to use the SCC even if an automatic calibration made by the SCC was not submitted yet. Anyway after a transition period it will be **NOT** possible to provide calibration constant using this procedure and the parameter :math:`\eta^*` can be calculated **ONLY** by the SCC as result of the submission of a proper calibration raw input dataset. The format of this input file is the same as the standard SCC input file. The only difference is that is should contain calibration measurements instead of standard measurements. Following our example, such file should contain the measurement performed at +45 and -45 degrees at 532nm. Also the channel IDs in the file should reflect the ones reported in table 3.3.
 Moreover this raw input file has to contain the variables:
 ::
 double Pol_Calib_Range_Min(channels)
-double Pol_Calib\_Range_Max(channels)
+double Pol_Calib_Range_Max(channels)
 where to specify the altitude ranges in meters in which the polarization calibration should be done.
+.. figure:: media/figure3.4.png
+:height: 806
+:width: 1896
+:scale: 100 %
+:align: center
+**Figure 3.4:** To provide polarization calibration (:math:`\eta^*`) values manually just use the button “Add polarization calibration” in the upper-right corner. This option will be available only for a limited period of time. After that only SCC calculated calibration constants will be accepted.
 According to the table 3.3 this file should be something similar to:
 ::
 dimensions:
 channels = 4 ;
-nb\_of\_time\_scales = 1 ;
+nb_of_time_scales = 1 ;
 points = 16380 ;
-scan\_angles = 1 ;
+scan_angles = 1 ;
 time = UNLIMITED ; // (3 currently)
 variables:
-int channel\_ID(channels) ;
+int channel_ID(channels) ;
-double Background\_Low(channels) ;
+double Background_Low(channels) ;
-double Background\_High(channels) ;
+double Background_High(channels) ;
-int id\_timescale(channels) ;
+int id_timescale(channels) ;
-double Laser\_Pointing\_Angle(scan\_angles) ;
+double Laser_Pointing_Angle(scan_angles) ;
-int Molecular\_Calc ;
+int Molecular_Calc ;
-int Laser\_Pointing\_Angle\_of\_Profiles(time, nb\_of\_time\_scales) ;
+int Laser_Pointing_Angle_of_Profiles(time, nb_of_time_scales) ;
-int Raw\_Data\_Start\_Time(time, nb\_of\_time\_scales) ;
+int Raw_Data_Start_Time(time, nb_of_time_scales) ;
-int Raw\_Data\_Stop\_Time(time, nb\_of\_time\_scales) ;
+int Raw_Data_Stop_Time(time, nb_of_time_scales) ;
-int Laser\_Shots(time, channels) ;
+int Laser_Shots(time, channels) ;
-double Raw\_Lidar\_Data(time, channels, points) ;
+double Raw_Lidar_Data(time, channels, points) ;
-double Pressure\_at\_Lidar\_Station ;
+double Pressure_at_Lidar_Station ;
-double Temperature\_at\_Lidar\_Station ;
+double Temperature_at_Lidar_Station ;
-double Pol\_Calib\_Range\_Min(channels) ;
+double Pol_Calib_Range_Min(channels) ;
-double Pol\_Calib\_Range\_Max(channels) ;
+double Pol_Calib_Range_Max(channels) ;
 // global attributes:
 :System = "mysystem" ;
-:Longitude\_degrees\_east = 15.723771 ;
+:Longitude_degrees_east = 15.723771 ;
-:RawData\_Start\_Time\_UT = "220000" ;
+:RawData_Start_Time_UT = "220000" ;
-:RawData\_Start\_Date = "20130620" ;
+:RawData_Start_Date = "20130620" ;
-:Measurement\_ID = "20130620po00" ;
+:Measurement_ID = "20130620po00" ;
-:Altitude\_meter\_asl = 760. ;
+:Altitude_meter_asl = 760. ;
-:RawData\_Stop\_Time\_UT = "230333" ;
+:RawData_Stop_Time_UT = "230333" ;
-:Latitude\_degrees\_north = 40.601039 ;
+:Latitude_degrees_north = 40.601039 ;
 data:
-channel\_ID = 10, 11, 12, 13 ;
+channel_ID = 10, 11, 12, 13 ;
-Background\_Low = 30000, 30000, 30000, 30000 ;
+Background_Low = 30000, 30000, 30000, 30000 ;
-Background\_High = 50000, 50000, 50000, 50000 ;
+Background_High = 50000, 50000, 50000, 50000 ;
-id\_timescale = 0, 0, 0, 0 ;
+id_timescale = 0, 0, 0, 0 ;
-Laser\_Pointing\_Angle = 0 ;
+Laser_Pointing_Angle = 0 ;
-Molecular\_Calc = 0 ;
+Molecular_Calc = 0 ;
-Laser\_Pointing\_Angle\_of\_Profiles =
+Laser_Pointing_Angle_of_Profiles =
 0,
 0,
 0 ;
-Raw\_Data\_Start\_Time =
+Raw_Data_Start_Time =
 0,
 300,
 600 ;
-Raw\_Data\_Stop\_Time =
+Raw_Data_Stop_Time =
 210,
 510,
 810 ;
-Laser\_Shots =
+Laser_Shots =
 1200, 1200, 1200, 1200,
 1200, 1200, 1200, 1200,
 1200, 1200, 1200, 1200 ;
-Pressure\_at\_Lidar\_Station = 1010 ;
+Pressure_at_Lidar_Station = 1010 ;
-Temperature\_at\_Lidar\_Station = 14 ;
+Temperature_at_Lidar_Station = 14 ;
-Pol\_Calib\_Range\_Min = 1000, 1000, 1000, 1000 ;
+Pol_Calib_Range_Min = 1000, 1000, 1000, 1000 ;
-Pol\_Calib\_Range\_Min = 2000, 2000, 2000, 2000 ;
+Pol_Calib_Range_Min = 2000, 2000, 2000, 2000 ;
-Raw\_Lidar\_Data = …...;
+Raw_Lidar_Data = …...;
 The file above assume the following calibration measurements have been done:
 1. First +45 degrees acquisition followed by a corresponding -45 degrees acquisition
 Shots: 1200
 As you can see there are 3 cycles of consecutive measurements at +45 and -45 degrees. That way the dimension :code:`time` is set to 3.
-The first +/-45 degrees measurement starts at “20130620 22:00:00” (start time of the first +45 measurement) and stops at “20130620 22:03:30” (stop time of the fist -45 measurement). As a consequence, according to the values of the global attributes :code:`RawData\_Start\_Date` and :code:`RawData_Start_Time_UT` we have to set:
+The first +/-45 degrees measurement starts at “20130620 22:00:00” (start time of the first +45 measurement) and stops at “20130620 22:03:30” (stop time of the fist -45 measurement). As a consequence, according to the values of the global attributes :code:`RawData_Start_Date` and :code:`RawData_Start_Time_UT` we have to set:
 :code:`Raw_Data_Start_Time[0]=0` (start of the first +45 measurement in
-seconds since :code:`RawData_Start_Time\_UT`)
+seconds since :code:`RawData_Start_Time_UT`)
 :code:`Raw_Data_Stop_Time[0]=210` (stop of the first -45 measurement in
 seconds since :code:`RawData_Start_Time_UT`)
 Following a similar procedure for the other 2 cycles we have:
 :code:`Raw_Data_Start_Time[1]=300` (start of the second +45 measurement in seconds since :code:`RawData_Start_Time_UT`)
-:code:`Raw_Data_Stop_Time[1]=510` (stop of the second -45 measurement in seconds since :code:`RawData_Start_Time\_UT`)
+:code:`Raw_Data_Stop_Time[1]=510` (stop of the second -45 measurement in seconds since :code:`RawData_Start_Time_UT`)
 :code:`Raw_Data_Start_Time[2]=600` (start of the third +45 measurement in seconds since :code:`RawData_Start_Time_UT`)
 :code:`Raw_Data_Stop_Time[2]=810` (stop of the third -45 measurement in seconds since :code:`RawData_Start_Time_UT`)
 :code:`Raw_Lidar_Data[2][2][points]` :math:`\rightarrow` 3\ :sup:`rd` measured transmitted signal at -45 degrees
 :code:`Raw_Lidar_Data[2][3][points]` :math:`\rightarrow` 3\ :sup:`rd` measured transmitted signal at -45 degrees
-Once this file has been created it needs to be submitted to the SCC and linked to the configuration “depol\_calibration”. The result of the SCC analysis on this file will be the calculation of the calibration constant h\ :sup:`\*` that will be logged into the SCC database and can be used to calibrate Raman/Elastic backscatter products (see section 3.3).
+Once this file has been created it needs to be submitted to the SCC and linked to the configuration “depol_calibration”. The result of the SCC analysis on this file will be the calculation of the calibration constant h\ :sup:`\*` that will be logged into the SCC database and can be used to calibrate Raman/Elastic backscatter products (see section 3.3).
 3.3 Definition of “Raman/Elastic backscatter and linear depolarization ratio”
 -----------------------------------------------------------------------------
 In order to calculate the *PLDR* we need to modify the polarization related products linked to the “standard” measurement configurations (the configuration called “nighttime” and/or “daytime” in table 3.2).
 As you can see in table 3.5, the old product IDs=3 and 6 (present in table 3.4) have been replaced with the new product ID=10 and 11 to guarantee the calculation of *PLDR*.
 It is important to set among the product options of the product ID=10 and 11 which calibration product we want to use for calibration (see section 3.2). This can be done using the SCC web interface setting the appropriate setting in the tab *Polarization calibration products* (see figure 3.4). According to the current example you should set here the calibration product defined in section 3.2.
-.. figure:: media/figure3.4.png
+.. figure:: media/figure3.5.png
 :height: 102
 :width: 1895
 :scale: 100 %
 :align: center
-**Figure 3.4:** How to link a product to calibrate with a calibration product.
+**Figure 3.5:** How to link a product to calibrate with a calibration product.
 .. warning:: Please note that also *Raman/Elastic backscatter products* need to be linked to a calibration product because the calibration constant and the corresponding correction factor is needed to calculate the total signal out of the two polarization components even if the *PLDR* is not involved in the product calculation.

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comparison: docs/depolarization/depolarization.rst

docs/depolarization/depolarization.rst