(This photo is the winning photo of the voyage)
The previous chapters introduced the basic knowledge of geomagnetism. Because the project is urgent, we can only learn the theory and deal with it. After 2 months of hard work, I basically mastered the basic method of ocean gravity and magnetic treatment. At present, the special gravity and magnetic processing are all prepared by the units themselves in accordance with the specifications. The main reason is: foreign software is not applicable, and domestic software is afraid to use it. Since his involvement in marine geophysics in 2017, two engineers from our unit, Zhang and Wang, have started to compile gravity and magnetic processing software, which has been improved without actual combat. The project is urgent, and everything is urgent. I asked for the software VC# project they compiled and started to deal with it. I am more familiar with C++, but I am not very familiar with C#, but it is not a big problem to understand the program. Most of the programs have no problems. A few problems are modified at hand, and the program is basically usable. Later, I really didn't hold back the itching of my hands, and compiled some auxiliary functions with VC#, and found that VC# is really easy to use. One line of VC# code is much more efficient than VB and VC. In the future, VC# is preferred for software compilation. The rules are correct, and the processing of ocean magnetic data will begin below:
(1) Use the auxiliary program to extract the time, position and speed course from the raw file of HYPACK
(2) Use, column alignment
(3) into Julian day
(4) to extract positioning data includes speed and heading
(5) Magnetic preprocessing
supra navigation data processing step
(6) extracting a magnetic data
(7) The navigation file edit track measuring line or
measuring line file The format is
line name, starting point longitude, starting point latitude, ending point longitude, ending point latitude
(8) Use the survey line segmentation program to finally generate sp_d4 and sp_t1 files (9) to convert into clm, which is convenient for MMDP processing
(10) Eliminate abnormal magnetic data (11) Calculate the normal field (12) Processing of daily variation First preprocess, extract the daily variation data, observe the daily variation data, eliminate time anomalies, then observe the daily variation curve, delete the abnormal interpolation of the data , and interpolate into Seconds are divided into single days, which must be interpolated and then divided, otherwise it will cause a lack of seconds and affect post-processing
(13) Daily change correction
//Calculate the time zone based on the longitude
Longitude/15, if the remainder is less than 7.5 degrees, then the quotient is the time zone; if the remainder is greater than 7.5 degrees, the quotient +1 is the
6th zone east of the time zone, and the local 23 o’clock is equivalent UTC 17 o'clock
East 8 zone, local 23 o'clock, equivalent to UTC 15 o'clock
(14) Ship magnetic file processing
According to the ship's magnetic center point, the calculation of the survey line file
is the same as the geomagnetic preprocessing, the ship's magnetic survey line clm is generated, and then corrected by the normal field Generate dlm (15) Calculation of ship magnetic component Ship magnetic correction coefficient (16) Calculate total intensity (17) Calculate magnetic anomaly Adjust according to the base value of two measurements, unified
(18) Adjustment, that is, calculating the difference of intersection
For more information, please visit xiaok marine surveying and mapping network or follow the public account of the same name