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--- tutorials:processing_gpr [2019/07/21 16:23] – dominique
+++ tutorials:processing_gpr [2019/07/25 10:44] (current) – [Examples] dominique
@@ Line 1: / Line 1: @@
 ====== Processing GPR data with SU ======
-Yes ! It is possible to process GPR data wit SU to apply all the power of seismic processing tools to GPR data.
+Yes ! It is possible to process GPR data wit SU to use all the power of seismic processing tools to GPR data.
-The basic trick is to fool SU by using micro second as the time unit and centimeters instead of meters. This way :
+The basic trick is to fool SU by using micro second as the time unit and centimeter instead of meter. This way :
   * frequencies are in MHz
   * velocities range from 3330 cm/micro sec (water) to 30000 cm/microsec (air)
@@ Line 15: / Line 15: @@
 There is no unified GPR data format and each manufacturer produces its own files. GPR data need to be imported from the manufacturer's format to SU format using the right tool.
-  * For [[https://www.sensoft.ca/|Sensor&Software]] devices you can use the ''dt1tosu'' tool included in SU
+  * For [[https://www.sensoft.ca/|Sensor&Software]] devices you can use the ''dt1tosu'' tool included in SU. (test and sample data needed)
-  * For [[https://www.guidelinegeo.com/products/category/gpr-solutions/|Malå]] devices you can download a shell script [[https://nextcloud.seismic-unix.org/index.php/s/kSZQyfqHLz5WdqN|here]]
+  * For [[https://www.guidelinegeo.com/products/category/gpr-solutions/|Malå]] devices you can download a shell script [[https://nextcloud.seismic-unix.org/index.php/s/L5NXLsWcjjeomr6|here]].It is included in SU44R15 and higher.
   * For other manufacturers, ask for the detailed format information and share the tool !
@@ Line 25: / Line 25: @@
 Compared to seismic data (apart from the recording or sampling time and size of the survey) GPR data exhibit a few differences.
-  * Absolute propagation time is generally unknown. Actually, GPR propagation is so fast that the receiver signal can't be digitized upon receiving a start signal from the transmitter, like in seimics. The source is fired at regular intervals and the digitizer is shifted by one sample at each pulse. The absolute time is not known but can be deduced when one knows the distance between antennas. Consequently you have to apply a static correction to GPR signal using ''sustatic''
+  * Absolute propagation time is generally unknown. Actually, GPR propagation is so fast that the receiver can't start diitizin when receiving a trigger signal from the transmitter, like in seimics. The source is fired at regular intervals and the digitizer is shifted by one sample at each pulse. The absolute time is not known but can be deduced when one knows the distance between antennas. Consequently you have to apply a static correction to GPR signal using ''sustatic'' to exhibit real travel time.
   * GPR signal is generally strongly polarized and affected by some very low frequencies caused by electronic noise. This is easily corrected by removing the mean of the trace (''sugain mbal=1'') and applying a high pass filter consistent with the antennas band-pass
   * The direct wave in the air (even with shielded antennas) and in the ground is very strong. It often saturates the analog to digital converter. They must be muted prior applying bandpass filters. This can be done using ''sumute mode=1'' or the dedicated ''sugprfb'' tool.
-  * The intrinsic attenuation of GPR signal is much faster (with respect to the wavelength) that for seismic signal and require the early application of a strong gain (with ''sugain'' or other techniques.
+  * The intrinsic attenuation of GPR signal is much faster (with respect to the wavelength) that for seismic signal and require the early application of a strong gain (with ''sugain'' or other techniques).
 ==== Final processing ====
-Like in seismics, there is no such thing as //standard processing//. Processing aims at mitigating noises that limit the usability of the data and is always a trade off between enhancements and negative side effects.
+Like in seismics, there is no such thing as //standard processing//. Processing aims at mitigating noises that limit the usability of the data and at enhancing primary reflected signal. This is always a tradeoff between enhancements and negative side effects which heavily depends on the data.
 === Band pass filtering ===
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 A time to depth correction (''suttoz'') gives a touch of finish to your data. Of course if you are using a constant velocity, it can be replaced by the right ''d1'' value in the trace headers. Since ''d1'' (and ''d2'') trace header words are floats, you can use them to label you data in meters instead of centimeters.
+===== Examples =====
+<WRAP center round todo 60%>
+Later... Be patient !
+</WRAP>
+ --- //[[dominique@seismic-unix.org|Dominique ROUSSET]] 2019/07/25 12:43// {{gravatar>dominique?l}}