Recording data
Since Hydromagic Survey version 6.0, sensor data isn't recorded directly to a sounding file, like it used to be in for instance, version 5.2. All sensor data is now time tagged with millisecond accuracy, and stored into plain ASCII text files, called raw data files:
example of a Hydromagic raw data file opened in Notepad.
Advantages of using raw data files
Time Tagging
In a sounding, position values are combined with depth measurements and possibly motion and tide correction data. Because the data is not received at exactly the same time, the offset between a depth and position measurement must be calculated. This is done when generating a corrected sounding file from a raw data file using the "Sounding Wizard".
Latency
In hydrography, latency is the time elapsed between receiving back a ping by the echo sounder, and the time the serial data containing the depth value is received and processed at the computer.
When this value is known (usually between 10 and 100 milliseconds), the delay is subtracted from the recorded timestamp to get an even better accuracy. The higher the speed of the vessel during a recording, the bigger the error because of latency will be. When you are not able to apply latency corrections, don't go to fast !
Data Security
Because the raw data is never altered after you complete recording data, you will never loose any data by performing invalid corrections to your data. Just use the "Sounding Wizard" again to edit your original data and create a sounding file which can be used for further processing.
Data Editing
Eye4Software Hydromagic keeps two copies of the raw data files on file. One copy is the original data, which is never altered, and the second one is the modified data. You can alter the modified raw data over and over again until your satisfied, and create a sounding file from it. If the data becomes corrupted, just revert back to the original data.
Flowchart of the Hydromagic software.