MagSurvey Software Operation

GETTING STARTED

Assure that the setup procedures have been completed, and that the sensor display shows as the correct horizontal distance behind the boat/operator (see the SETUP help topic for a discussion of the importance of proper sensor positioning – this will have a direct bearing on the accuracy of survey results).

When the sensor is positioned properly and is returning good data, click on Zero Mag (or press the Page Up key or press the Alt-Z keys).  This will zero the magnetometer graph and establish a reference gamma reading.  It is not necessary to "Zero Mag" if using a metal detector -- instead, adjust the metal detector to the proper gain and offset.

With the boat in motion and with the sensor tracking directly behind, when a convenient starting point for the survey is crossed, click on Set Origin (or press the Page Down key, or press the Alt-O keys). This will display a notice indicating to the operator to click on a screen starting point. This will now be the current position of the boat’s GPS antenna. The objective is to select a screen position based on the anticipated search area to be covered. If the starting point is a detected anomaly, it may be convenient to select a starting point in the center region of the screen. East-west parallel tracks are recommended for the survey where practical.

The View 2D/3D Chart button can be used at any time to alternate between viewing the 2D or 3D chart.  The 3D chart is used for graphic visualization of anomalies, whereas the 2D chart is used for accurate and dependable navigation.

RUNNING PLOTS

CAUTION: MagSurvey is not to be used for primary boat navigation. The blank screen background does not mean that there is sufficient depth of water for navigation, or even that there is water at all. MagSurvey simply provides directional and earth-positional information – the boat operator must keep a constant watch for obstructions and depth of water. MagSurvey neither steers the boat nor operates the throttle, although both would be possible in a world without litigation excesses. Perception Systems, Inc. is not responsible for damage to the boat, sensor, property, or any living beings.

The boat’s GPS position is indicated by the four cyan corners on the plot window, while the sensor position is indicated by the four yellow corners. The arrow pointer may be moved around in the plot window, and its location is displayed -- along with data pertinent to the location. The pointer latitude and longitude values indicate the center of the map element beneath the pointer.

Once the magnetometer has been zeroed, the origin has been set, and good data is being received from the magnetometer, GPS, and differential correction source, the Start Logging and Stop Logging buttons are used to allow logging of anomalies and map element positions visited. It is important to Stop Logging whenever the sensor is not tracking directly behind the boat’s displayed track-over-ground (TOG). The Home and End keys will also start and stop logging, respectively. Any time the magnetometer’s sensor is within a map element, the largest peak positive and peak negative anomalies are compared to any previously-recorded positive and negative peaks, and the resultant stored values are the most positive and most negative values sensed within the map element.

For marine surveys, since  the computed sensor position is determined from GPS track-over-ground information (TOG), care must be taken to assure that the boat always has a positive forward motion whenever logging is enabled.  Maintaining speed-over-ground (SOG) of one knot or greater is recommended (faster if there are currents present).

For best results, it will be necessary to re-zero the magnetometer from time-to-time to cancel-out unwanted drift due to natural gradation of the earth’s magnetic field, diurnal changes, sunspot variations, and small errors due to direction and proximity to the boat.

MARKING LANDMARKS  AND OTHER POINTS OF INTEREST

During plotting operations, points of interest, such as property borders, permanent buoys, etc., can be recorded on the 2D plot screen by clicking the Mark Plot button while located at that point of interest.  The background for the point shows as a lighter shade of gray.

ERASING BAD DATA

During plotting operations, if a known error is logged at a map element due to a magnetometer glitch, towing problem, or other situation, the data for that map element may be erased by positioning the pointer over the map element and double-clicking with the pointing device. A unique pattern is displayed at that position for the duration of the survey to show that data has been erased.

SAVING PLOTS

Survey data can be easily saved as often as desired by clicking the Save Survey button (the Alt-F followed by Alt-S keys may be used to obtain the same results).  A message box will appear to assure that a save is intended – Click OK to save the plot and all data. The name of the saved file includes the full date and time of saving for unmistakable and chronological file identification. The filename consists of a letter (F for extra coarse scale, E for coarse scale, R for rough scale, D for default large scale, C for medium scale, or B for small-scale), followed by a four digit year number, followed by a two digit month number, followed by a two digit day number, followed by the letter "T" (for time), followed by a two digit hour number (military 24-hour time), followed by a two digit minute number, followed by a two digit seconds number.  The saved survey files are located at C:\MagSurvey\Surveys, in case you wish to back them up later to other storage.

RETRIEVING PLOTS

NOTE: Retrieving a stored survey will wipe out any on-screen plot data – if there is any data on the screen that should be saved, select Save Current Plot Survey first.

Any previously-recorded survey can be quickly loaded by clicking File selecting Load Previous Plot Survey, and selecting one of the options below. These menu selections are located in the upper left corner of the screen (the appropriate Alt-key codes may be used to obtain the same results). Two operational modes are supported.  MagSurvey must be set to the compatible scale for the file that you wish to load.

Review Mode -- The file will be loaded, and the boat/operator's current and subsequent positions will be superimposed for analysis, or for navigation. On-screen displays indicate the distance and bearing of the boat to any map element beneath the arrow pointer. In review mode, an option to save the on-screen survey as a bitmap image becomes active under the File menu at the upper left corner of the screen.

Append Mode – The file will be loaded, and the current and subsequent positions of the boat/operator and sensor will be superimposed for the purpose of adding to a previous survey that may be incomplete. As with the other modes, the distance and bearing of any map element is indicated on screen when a map element is selected by the pointer.

NEW PLOT SURVEY

NOTE: Selecting New Plot Survey will wipe out any current on-screen survey data – if there is any data on the screen that should be saved, select Save Current Plot Survey first.

A new plot survey can be begun at any time by clicking File and New Plot Survey in the upper left corner of the screen (the Alt-F and Alt-N keys may be used to obtain the same results). The screen will be cleared and a new origin must be set.