BARTINGTON INSTRUMENTS
Page 42 of 61 OM1800/26
Note:
After restarting, if the survey parameters are changed before continuing with the
interrupted Grid then the data may be saved in the wrong format and false results may be
seen.
Note:
If a download is attempted with a Grid still incomplete then the last Grid will
download continuously. If the number of downloaded bytes exceeds 260 000 then the
download should be interrupted manually. Only complete Grids can be downloaded.
Data values are stored as two-byte signed integers to minimise both the memory requirements
and the time taken to download data. The decimal points are added in the appropriate place by
the download software using the range information in the Grid header. The 256kByte memory is
sufficient to hold the data for 36 Grids of 30x30m with a line separation of 1m and 4 readings per
metre. This corresponds to 36 Grids, each with 3,600 data points. If smaller Grids are used or
measurements are made at less frequent intervals then the capacity of the memory will increase
proportionally up to the limit of 99 Grids. Dummy values take up the same memory space as real
values, and finishing a Grid with dummies utilises the same memory space as a normal Grid.
To place the data into a larger matrix after downloading, the operator must record the relative
position of each recorded Grid separately.
18.1.2. Single Shot Operation
If
Single Shot
is selected as
Pace
in the
Set parameters
menu (between 2 and 0.5m/s) then the
survey operates as normal, except that only one reading will be recorded each time the operator
presses and releases
ENTER
or the green button, rather than data being recorded at a fixed rate.
The gradiometer can then be moved between individual readings.
19. Downloading Survey Data to a PC
Contents of the memory can be downloaded to a PC and each Grid saved to a file with one of
three formats (see
File Formats
). All data recorded in a zigzag pattern, or with interlacing as for
2 or 4 lines/m using a dual sensor gradiometer, will be re-arranged automatically to appear as it
would if recorded in a parallel pattern with the correct line order.
Grad601 Datalog software for this purpose is supplied with the Grad601 gradiometer on CDROM.
It is also available for download on the Bartington Instruments website. Other proprietary data
processing software, such as TerraSurveyor from DW Consulting, allows direct download from
the gradiometer into the program ready for processing.
If using the NMEA data logger, the recommended software for collecting the Grad601 and GPS
data is Trackmaker (by Geomar Software, Canada). This is an ideal solution for the processing
of the data. If using more than two sensors, for example when using with a cart system,
MultiGrad601 (Geomar Software) can be used. Any other software that can interpret NMEA data
and combine the magnetic and GPS data will also work.
