G-858BP Backpack Mag
Operators Manual
Appendix 3: Advanced Information
This information is supplied for those interested in some of the more technical aspects of the G-
858BP. Look in this chapter for some answers to frequently-asked-questions.
Memory Usage
Inside the G-858BP, readings and positions (Marks and Lines) are simply stored sequentially, with
a time stamp. The MagMap2000 program will put the first reading following a mark exactly at that mark.
The last reading before a Line event will be placed at that position.
Readings average about 3 bytes each, and positions about 10 bytes. GPS strings average about 30
bytes per reading. There is 1 Mbyte of memory in the standard unit, 2.5 MB in all units with the new CPU
board that support 4 com ports. There is no limit to the memory used by each file.
Some memory is wasted by using additional files. Each new file must start on a 64K boundary.
An average of 32K will be wasted, then, by opening each additional file.
File Formats
The following information is supplied for those users who wish to perform manipulations on the
data beyond that which MagMap2000 is capable of. This section will explain the various file formats used
in the data analysis process.
Binary File
This file has the .
BIN
extension, and is a raw dump of the data contained inside the memory of the
G-858BP. This data is not stored in a user readable format. It is compressed in a manner unique to the
requirements of the operation of the G-858BP. Furthermore, each new revision of the G-858BP firmware
may cause changes in this file format. Do not attempt to modify files of this type.
ASCII File
This file has the .
STN
extension, and is in a user-readable format. This file is created by the
program
BINTOASC.EXE
. This program is run with the default parameters from the MagMap2000
program. It may also be run directly from the DOS prompt, and given many options which will adjust the
format of the output. Please see the section later in this appendix describing the operation of
BINTOASC
.
The ASCII file contains lines which are a record of events from the perspective of the G-858BP.
Events may be either magnetometer readings, MARK, END LINE, or PAUSE key presses, RS-232 input
strings, or field notes. Each event is recorded in the order it was received, and given a time stamp.
Note:
The ASCII file lists these events backwards in time, i.e., last-in-first-
out.
Each line in the ASCII file starts with a number, referred to as the TYPE in the following
discussion. The TYPE indicates what information follows. The table below shows the TYPE for each of
the events.
TYPE Event
0 Magnetometer
Reading
3 Position
Event
6 Discontinuity
Event
9
PAUSE key press
12
UNPAUSE key press
21 RS-232
string
33 Field
note
92