ppm utility program description 1....
TRANSCRIPT
PPM Utility Program Description
(Version 27/11/2014)
1. Introduction
This program runs on Windows-based systems (XP, W7) to manage resources and remote
control a PPM loaded with the MarkVII version of Firmware.
It is able to control and manage any PPM MarkVII configuration (Basic LCD-based,
Optional GUI-based or Blind) by connecting to its specific serial control link.
For all types of PPM configuration, the program remotely manages the system
parameters and the Survey Grid files. For Blind systems (no User interface device), it is
also their unique but comfortable and sophisticated User Interface. This case is
especially designed for underwater survey systems. (These systems can also optionally be
equipped with a Bluetooth channel to connect the PC to the PPM box).
2. Installation procedure
The installation package is available on our Web Site here:
'http://users.skynet.be/fa352591/PPMUtilityVBNET.zip' .
You should download it and unzip it in a user accessible folder of your XP or W7 system.
If the program has already been installed on the same system, it must be de-installed now using the
'Manage Programs' tab of the Windows Configuration Panel.
Run the SETUP.EXE program contained in the unzipped folder.
It will install all the necessary components and files and create a shortcut in the
start program list.
If you are using a USB-to-Serial cable from FTDI, you will also need to execute the FTDI
driver installation from here : 'http://users.skynet.be/fa352591/FTDI_Setup.exe'
This will install the drivers necessary to communicate to the PPM through the USB-to-
Serial cable.
If using a Bluetooth link, you need instead to install the Bluetooth device (with the PPM powered on)
using the standard Windows procedure (hidden icons at bottom of the windows screen).
The pairing code to be used with our Bluetooth module is '1234' and its ID is 'HC-06'. I
3. System parameter Setup
• Initial Setup
At first execution of the program, it will create a parameter file named DEFAULT_P.TXT in the newly
installed directory path.
The Application Data folder is automatically created and the factory-based Default file is copied in it.
The System Parameter file (GLOBAL_P.TXT) is also missing and is created empty.
The Main program screen is displayed.
Click on the 'Parameters then, 'Edit Global_P' menus to get the following screen:
Click on 'Reset GLOBAL_P From DEFAULT' button to reset the Global parameters to default values
Click on the 'Save to PC and PPM' button.
You will see this warning message popping up for a few seconds since there is not yet any
PPM connected and powered-up:
• Updating Global Parameters
The usual global parameters to be set are displayed in the GLOBAL_P Edit Screen.
- The Local B value will be automatically set by the tuning process described later in this
document.
- The Operation Mode and the GPS Option selection panels are used when changing of
operation mode. At this time, leave them with their default values.
Important: If you modify the operation mode or the
GPS Option, you should first save the modified value
as usual but you must also exit the PPM Utility
program and power OFF and power ON the PPM
system.
- The Gradient Threshold defines the threshold expressed in nT over which a field gradient will generate an audible warning with the buzzer.
- The Gradient Filter is used to define the number of seconds of previous readings
to calculate the difference between the average of those previous readings and the
latest reading, this difference being called 'field gradient'.
- A small positive value (like 4) will only generate field gradients when the average
value of the few previous readings are different from the latest reading. This
will remove the slow variations of magnetic field over the whole survey but
emphasize the quick variations of field generated by targets.
- A larger positive value (like 255) will use many previous readings to calculate the
average. Thus, the field gradient will show the variations of magnetic field
compared to the average field value over the whole survey.
- A negative value will trigger a target detection based on the rate of the absolute
B field variations expressed in nT/second. All variations slower than this value will
be ignored and the gradient will be set to zero. Example: a value of -10 requests all
variations faster that 10nT/sec to be displayed and slower variations ignored.
- The Towing Rope Length is only used for underwater surveys based on GPS fixes, it is used
to correct the GPS fixes taking into account the azimuth of the course and the length
of the towing cable and calculate the actual GPS fixes of the sensor and not of the boat.
• Updating Default Parameters
The full default parameters are displayed in the 'Edit DEFAULT_P'
Screen.
This screen displays all the system parameters with the values which will be set when
pushing on the 'Reset' button.
The initial values are factory-based but an expert can modify them provided he knows
what he is doing.
To get more details about these parameters, go to the full operator manual of the PPM
MarkIVB.
4. Connecting PPM system
The PC is connected through any of its COM port (including through 'Serial to USB'
or through Bluetooth module devices.
Select the required connection type and the COM Port#
Make sure the connected serial link is present and its communication parameters are
correctly set using the Peripheral management tab of the Configuration Panel.
When using a serial-to-USB device, it must at least be plugged in the USB socket to be
seen by the Windows system.
Connect the cable to the PPM and power up the PPM. Click on the 'Conn./Setup' menu (see
screen dump at end of page). Select the correct 'Connection Type' and click on 'Connect'
button.
You must now see a quick scan of all the COM links known by Windows. When one of them
correctly answers to the WHO-ARE-YOU message, you will get this type of popup message:
If a GLOBAL_P file was found on the SD Card, the text of the Information box will be:
The connected COM number has been recorded and it will be used first for the next
times you connect the program.
The two systems are now successfully connected and ready to cooperate.
The default title of the main control window of the program is replaced by the date of
the last Build of the PPM firmware.
5. Remote Survey File Management
In order to review Grid files from the SD Card on the PPM, click on the 'Grid Files'
menu. You will get the following dialog box:
Selecting one file on the list and pushing on the 'Upload' button will upload the selected file in a selected folder of the PC.
'Edit' button will open and display a file using Notepad.
'Erase' button will delete the selected file on the SD Card of the PPM.
Note that most of the grid files will already be sitting on the PC if they were captured
in real-time by the PPM Utility program.
6. Tuning Management
Tuning will measure the local value of the earth magnetic field and set the parameters
of the system accordingly. Go to the operator manual to study the details and
precautions to take before doing a tuning process.
Tuning is started by pushing on the 'Tuning/Start' menu of the main screen.
The main screen will modify its contents as follows:
The long information grey line is the Application Data path where a text file has been
written.
This file can later be read by pushing on the 'Tuning/Review' menu entry. Its content
will display in Notepad.
This is a commented contents of a typical FRxxxx file: The three following lines are just a copy of the corresponding lines in the parameter file
'$SL18.3 'This is the inductance of the sensor
'$ST328.0 164.0 82.0 47.0 22.0 10.0 4.7 'This is the list of the tuning caps
'$SG30 'This is the amplifier gain 'Noise:18mV 'This is the ambient noise level in mV
The following three pairs of lines are the results of three consecutive FFT processes which evaluate the
local precession frequency with the UNTUNED sensor. You can see that the three tests gave the same frequency (2056Hz) corresponding to 48290nT The resulting tuning cap value is 327nF given the sensor inductance of 18.3mH 48290nT->327nF F:2056Hz,M:220109 48290nT->327nF F:2056Hz,M:205586 48290nT->327nF F:2056Hz,M:225350 The average is taken from the three attempts and the tuning switch is set to HEX 3E from the
calculations Average:48290nT->327nF,OK/UP $AT set to 3E Now, an optimization of the tuning is executed. A sequence of normal polarizations and readings are made with the 8 tuning values around the calculated
tuning For each attempt, the S and M values are calculated and displayed. The best tuning is the one which
gives both the lowest S and the highest M. $at 3E=S:0.8,M:0173 $at 3F=S:2.1,M:0131 $at 3D=S:2.1,M:0273 $at 40=S:1.7,M:0166 $at 3C=S:0.9,M:0325 $at 41=S:2.7,M:0100
$at 3B=S:0.8,M:0238 'In this case, the optimized tuning should be 3B since it gave the lowest S and
highest M
$at 42=S:1.7,M:0113 $END a $TB Autotuning=3E $SB 48290 $END At the end of the FFT process, the $at line with the best Figure of Merit (FOM = M value/S value) is selected.
If you agree with that selection, just push on the button 'Set AT' and push on the
button 'Exit FFT' to terminate.
If you want to set another AT value, select another line of the list and push on the
two buttons in the same sequence.
After this process is terminated, you can start a first session with the calculated or
your selected tuning values. This is guaranteed to work well.
However, you could always set another tuning in the $AT parameter of the GLOBAL_P file
in order to get the best from your system at that location.
Re-tuning should only be required when you have changed of region as far as 100 or 200km.
This is the list of actions and results coming from the tuning process as well as the
initial values which were used to make the calculation.
The final two lines show the Auto-Tuning (AT) parameter value and the Local B (SB) value.
These values have been automatically set in the GLOBAL_P parameter file.
The long information grey line is the Application Data path where a text file has
been written.
This file can later be read by pushing on the 'Tuning/Review' menu entry. Its content
will display in Notepad.
7. Real-time Survey Session Management
• Non GPS based Operation modes (Static, Mobile, Base)
A real-time session is started by Clicking on the 'Viewer' button of the main
screen. The following screen will be displayed. Select now on the 'SESSION/Start Session' menu.
The following File Save Path Selection screen is displayed showing an automatically-
generated file name with a current timestamp formatted as 'GDddhhmm.TXT' in the
default data folder.
It is the survey grid file where the readings will be stored.
Pushing on the 'RUN' button starts the session.
- The UTC field shows the reading timestamps in seconds.
- The Field Gradient is displayed in Green if the S is smaller than 20
- The Field gradient values are plotted horizontally.
Pushing on 'PAUSE' button temporarily pauses the session and selecting
'SESSION/Start
Session' menu resumes it.
During a pause, clicking on any point in the PPM plot will display the corresponding values of
the timestamp, possibly the row/column if operation mode is 'Mobile' and Field
Gradient there.
Select the 'SESSION/Stop Session' menu to terminate the session and close the output file.
• GPS-based Operation modes (GPS or UTM)
The GPS-based operations can be supported by the GPS module internal to the PPM
control box or by an external GPS device connected to the PC through USB or Bluetooth.
The internal GPS is set by setting the GPS Option (GO) to 'GPS' and the Op. mode (Xn)
to 'GPS' on the system parameter window.
The external GPS is set by setting the GPS Option (GO) to 'GPS', the Op. mode (Xn)
to 'Static' and check the 'GPS on PC' mark on the system parameter window.
Do not forget to save to PC and PPM and to stop and restart the PPM control box.
The GPS fixes will be sent to the PC program as soon as the 'SESSION/Start Session' menu has been pushed and a destination grid file name and directory has been selected.
As an indication of this, you will see first a GREEN or a RED blinking "I AM ALIVE"
LED indicator.
Just after power up, if the system was left without power for a long time, the super-
cap used as storage by the GPS chip will have discharged and its content lost. In that
case, the GPS will make a 'cold start' and the latitude/longitude will display null values
until the boot is terminated and the blinking indicator will be RED, this could take a
minute or two.
If the system was not powered down for a long time, then, the GPS will only make a
shorter 'warm start'.
The SV value is the number of satellites in view. You should wait until you get at least
7 there to get a good precision on the fixes.
You should wait until you get a value of HDOP (Horizontal Dilution Of Precision) close to 1
to get a good precision on the fixes.
However, as soon as you see non-null latitude/longitude values and the blinking indicator in
GREEN, you can start a session by pushing 'RUN' button.
When visible GPS satellites are close together in the sky, the geometry is said to be weak and the Dilution Of Precision (DOP) value is high; when far apart, the geometry is strong and the DOP value is low. Thus a low DOP value represents a better GPS positional accuracy due to the wider angular separation between the satellites used to calculate a GPS unit's position.
Note: With an HDOP <= 1 and SV >= 7, one can expect an average global fix precision of less
than one meter. In full open country or at sea, SIRFIII GPS devices will usually give
that quality of fixes or even better. This range of precision is valid for the PPM
surveys over wide area where a GPS support is needed (e.g. underwater surveys).
Pushing on the 'RUN' button starts the session.
- The UTC field shows the UTC from the GPS.
- The longitude and latitude are displayed in decimal degrees with a precision of 7
decimal positions.
- The altitude in meters and Azimuth in degrees are displayed.
- The Field Gradient is displayed in GREEN if the S is smaller than 20 otherwise it is
set to 99999 and colored in RED.
- The Field gradient values are plotted vertically. The field gradients are calculated
using the current value of the $GF parameter but it is possible to override it by
temporarily changing this value in the Viewer screen (see the text field labeled 'GF')
- The GPS fixes are plotted in XYZ mode using one of two possible options according to
the checkmarks in 'Draw Shape':
1. Hollow or Filled circles whose diameter depends on the field gradient and color depends
on the sign of the gradient, Green for positive, red for negative values.
2. Circles of diameter depending on the absolute value of the gradient and filled with
a rainbow-type color scale. Hot colors correspond to positive field gradients, cold
colors correspond to negative field gradients. Light green shows field gradients close
to 0.
3. Lines whose thickness depends on the field gradient and color depends on the color scale.
In all cases, field gradients with absolute value is less than the Gradient Threshold parameter ($TG) will be displayed with very small diameter or thickness.
Pushing on 'PAUSE' button temporarily pauses the session and pushing on 'RUN' resumes it.
During a pause, the Latitude/longitude, SV and HDOP values and the GPS plot are still
refreshed every seconds but the readings are stopped.
In PAUSE mode, the GPS fixes are displayed on the GPS plot area as small blue
crosses instead of green or red circles.
Clicking on any circle in the GPS track plot will show the corresponding point in the PPM
plot with an horizontal black line and will display the values of the UTC, the
latitude/longitude and Field Gradient there.
Clicking on any point in the vertical PPM plot will show the corresponding GPS track circle with an large black cross.
Select the 'SESSION/Stop Session' menu to terminate the session and close the
output file.
By default, the plotting has an automatic panning and scaling to show the complete survey
data.
Dragging the plot (i.e. pushing on LEFT mouse button, moving the mouse and releasing the
button) makes the panning of the plot. Pushing on the RIGHT mouse button pops-up a
context menu which allows Zooming in/out.
The 'automatic dimension' mode is stopped when panning or zooming were activated.
The 'Center' checkmark makes all the new readings to be displayed from the center of the GPS plotting window and will be plotted with the latest scale ratio.
The 'CAP' also makes all the new readings to be displayed from the center of the
GPS plotting window. This selection is only really effective when a MAP has been
loaded as background of the GPS plot (see later the GEO referencing chapter).
It is possible to combine the GPS plot of an existing grid file with the real-time GPS plot. You first display an existing grid file (using the Review function described hereunder '8.
Review Survey Files') and then you can relocate the potentially interesting points
or Waypoints by starting a real-time session and keep it in pause mode. During this
mode, the GPS fixes will display as blue crosses. This enables the boat driver to
control the azimuth in order to get close to a selected Waypoint.
Clicking on any point of the GPS plot or any point on the PPM reading plot with the
RIGHT mouse button will pop-up a context menu giving the choice to generate a new
Waypoint, to start a GPS tracking process or to Zoom IN/OUT.
If the 'GPS Track' item is selected, then the current GPS coordinates are used as
the reference (Target) for all later GPS tracking.
During GPS tracking, a popup window displays the Azimuth and the Distance between the
current GPS position to the Target Waypoint. It also shows the Course-over-Ground given
by the GPS (COG is the azimuth of the GPS course).
It also shows a compass with two needles, one to point to the azimuth to follow to go to
the waypoint and one showing the azimuth given by the GPS as COG.
There is also a graduated scale of 50 meters wide and one of two yellow values shown
either to the right or to the left. If the current position of the GPS is located right on
the straight line between the starting point of the navigation and the ending point (the
Waypoint) then, there is a red triangle in the middle of the scale and the yellow value is 0.
If there is a gap of n meters from that line to the right, the red triangle is shown at n to
the right and the yellow value is n and located to the right.
This means that the system has to be driven to the left until the yellow values becomes
zero.
If the gap is larger than 25m (as on the following picture), the red triangle disappears
but the yellow value still shows it as a decimal value.
The GPS tracking can be used to go back to a potential target detected during a
previous survey session or it can be used to control the boat to follow a survey line
during a real-time survey session.
If several Waypoints have been generated either manually by clicking on a spot on the
GPS plot area or by the 'Create Grid' function and if the distance to Target decreases
to less than 10m (30ft), then the next waypoint on the list is automatically selected and
the GPS tracking is now directed to this new Waypoint.
When several waypoints have been marked on a given session, the target relocation is made
faster by generating the shortest route between all these waypoints.
This is done by pushing on the 'Short Route' menu on the 'GPS Tracking' window.
This will start from the current GPS position of the system and look for the Waypoint
closer to that position. It then generates a first route segment. Then, starting from this
waypoint, it looks for the next closer waypoint and generates a second route segment, and
so on. At the end of this process, the list of route segments is available on the combo box
of the 'GPS Tracking' window and they are sorted in the proper sequence.
The target relocation mode can then be used with the optimum efficiency.
Each time a route segment has been terminated, it has to be deleted to display the
next segment on the combo box.
8. Session control through simplified User Interface
The Full Viewer window is feature-rich but rather crowded. A simplified user interface
was requested for the real-time survey and target relocation sessions.
This interface has been designed to fit easily in a 8" tablet screen. The tablet
being optionally linked to the PPM control box and to an external GPS through
Bluetooth. There are now Windows 8.1-based 8" screen tablets appearing on the
market. This screen size is more readable and comfortable than most of the smart
phones and is still small enough to be carried in one single hand (more specially in its
vertical orientation). Thus, there were two distinct operation modes defined with
this interface.
1. Survey session with or without navigation support
The PPM group displays the most important captured data and monitoring values. The GPS
group displays the captured GPS data and optional Navigation support info.
2. Target relocation with Navigation support.
The PPM group is not displayed. Actually, if the GPS support comes from an external GPS
device, there is not even any need to carry the PPM control box. The GPS group displays the
captured GPS data and associated Navigation support info.
9. Post-Processing Survey Files made in Multi-line mode
Survey files captured in Multi-line grid mode need to be post-processed before
being plotted.
These files give a row# for each measured point but no column on the grid.
Survey sessions must be made in such a way that the second and all next rows should
be made to the left of the first row.
Given the actual length of each row, the post-processing regularly spreads the measured
points over each row with a distance depending on the number of point on a row and its
length.
The resulting file gives a set of relative coordinates for each point (i.e. starting at
row#0 and col#0 at its bottom left corner).
This file can then be used to generate a true grid using the Viewer function found in
the menu 'Session/Make Grid'. It will generate a simple rectangular grid whose
coordinates are expressed in relative meters or any other measurement unit.
Survey sessions may be made with a distance between rows which could be lower or higher
than one unit of measurement. For instance, a distance of 0.5m for surveys which require a
higher precision. In that case, the row coordinates will step up by 0.5 unit at a time.
Survey sessions are not always of rectangular shape, they could have any form of polygons
like trapeze, triangle,...
These cases can be taken care of by the post-processing given a parameter file giving
for each row the offset of its first measurement and the length of that row. The
offset and length are expressed in the chosen unit of measurement (meters, feet,..).
Lastly, the complete survey session can be geo-referenced by converting the relative
coordinate system into true GPS coordinates. This process requires to give in the
parameter file three reference points in GPS coordinates.
The first point should be the first reading of the first row of the session.
The second point must be the last reading of the first row.
The third point must be the first reading of the last row of the session.
Examples Col # Col #
- 4 - 3 -2 - 1 0 1 2 3 4 5 •12345679
3 P3 4 P3
• 3 • • • •
Row # PP1 P2 P Row # •
P1 P2
P1 = 0,0
P2 = 0,5
P3 = 3,-3
row# offset length
0 0 6
1 -1 7
2 -2 7
3 -3 7
P1 = 0,0
P2 = 0,9
P3 = 4,4
row# offset
length
0 0 9
1 1 7
2 2 5
3 3 3
4 4 1
The post-processing of a survey file is started from the menu 'Tools.../Process Multiline'
on the Main window.
This first requires to select a survey file on its folder.
A parameter file is looked for in the same folder. Its name is the same as the one of
the survey file but extended with a 'P'.
If not found, a default parameter file is created and the survey file is read to record
the number of rows and the number of points for each specific row.
This is an example of the parameter setup window :
It corresponds to a survey file with 11 rows (marked 0 to 10) with a width of 10 meters and
a length of 20 meters.
By default, it has a rectangular shape and is not geo-referenced.
If such a parameter file already exists in the same folder, it is loaded and displayed like the following:
This corresponds to a survey file with 11 rows (marked 0 to 10) with a width of 20 meters
(thus, a distance between rows of 2 meters) .
It has a convex polygonal shape and it is geo-referenced.
The parameter file is as follows:
20,20 4.368906,50.530237 4.36916,50.53017 4.368954,50.530322 0,1,19 1,1,19 2,2,20 3,2,20 4,2,20 5,-1,20 6,0,20 7,0,20 8,0,20 9,0,20 10,0,20
10. Post-Processing GPS Survey Files to improve the GPS precision
The GPS coordinates generated by a standard GPS Module (like the one integrated in
the PPM box) are subject to slight variations due to various atmospheric influences.
This can only give an average precision of 5 to 10 meters. This precision is sufficient for
the surveys made at sea to discover large shipwrecks but it is not sufficient to locate
underground targets. In the latter case, we should get a sufficient precision to locate
a target within a circle of one meter or less.
There are some special procedures to improve the GPS coordinates in real-time or with
some post-processing. The real-time procedures use a world-spread GPS stations (Beacons)
which continuously broadcast their corrections through radio links. These services are not
free, they need a subscription and they need a specific radio receiver.
The simplest and less costly procedure is to setup his own GPS-based fixed station
located near the survey area at a location whose precise coordinates are known.
One way to do this is to use a fully differential configuration using two distinct PPM's,
one fixed and one mobile. See the following chapter 10.
It is also possible to setup a fixed station using a simple GPS device with a NMEA
logging made by a specialized GPS logger system or a PC running a GPS logging program or
even a simple terminal emulator able to capture and record the NMEA data stream on a
file. First, power up the GPS at the fixed station during a few minutes without
recording in order to give it the time to synchronize to a maximum of satellites in view
and get the optimum
precision. Do the same with the GPS on the PPM before starting a survey session. When
you get an HDOP of 1 or less, the two GPS are ready to operate with precision. Select the
location of the fixed station with a full view to the open sky and a location where you can
get its precise GPS coordinates. To get precise GPS coordinates, you could use a geodesic
GPS device or the coordinates picked up from a map or Google View based on an obvious field
reference.
Now, start the file capture on the fixed station and start the survey
session. At the end of the survey session, you stop first the survey of the
mobile station then, the file capture on the fixed station.
The procedure to apply the corrections to the GPS coordinates of the survey session file
is the same as the one applied in following chapter 10.
The Base station will record the slight variations of GPS fixes compared to its actual
global positioning. These variations will be applied on each corresponding fix captured by
the mobile station in order to correct it.
This post-processing is executed by selecting the main menu entry 'Process GPS'.
A file open dialog box will first ask to select the MOBILE grid file, then, the NMEA
file captured by the base station, then, the exact coordinates of the base station,
then, the destination file to be created (by default, the same as the mobile file name
with an appended 'G').
11. Post-Processing GPS Survey Files captured in Differential
mode
In order to make surveys with higher precision in both X,Y and Z values, it is necessary
to use two distinct PPM, one set as a base (fixed location) station and one as a mobile
station carried on the survey grid. The readings of the two PPM are naturally
synchronized by their common UTC values.
The Base station will record the slight variations of GPS fixes compared to its actual
global positioning. These variations will be applied on each corresponding fix captured by
the mobile station in order to correct it.
The Base station will record the slight and slow variations of magnetic field in a
fixed location near the survey grid area. These variations will be applied on each
corresponding PPM reading captured by the mobile station in order to calculate the
precise field gradients compared to the absolute field measured by the base station. This post-processing is executed by selecting the main menu entry 'Process GPS'.
A file open dialog box will first ask to select the MOBILE grid file, then, the BASE grid
file, then, the exact coordinates of the base station, then, the destination file to be
created (by default, the same as the mobile file name with an appended 'G').
This is an extract of such a file:
GPS_SESSION:30/4/2012-11:54:26,4.3690080,50.5302820,GD000001,
50mS, 650mS,40x,48384nT,1000mS, 255,
$ 4.3690186 50.5307465 115431 -12.7 0.8 48270.6 216 0.6 48283.3 422
$ 4.3690214 50.5307465 115432 -8.5 0.7 48274.8 243 0.6 48283.3 422
$ 4.3690233 50.5307503 115433 -5.9 0.6 48277.4 266 0.6 48283.3 422
$ 4.3690243 50.5307503 115434 10.9 0.3 48294.2 322 0.6 48283.3 422
$ 4.3690252 50.5307503 115435 -17.3 0.7 48266.0 308 0.6 48283.3 422
------------------------------ --------- ------ --------------------- ----------------
-----
Corrected UTC F ie ld S,B,M of S,B,M of
longitude/latitude Gradient Mobile Base
12. Reviewing Survey Files
Select the 'SESSION/Replay Grid' menu on the Main screen to review existing grid
files.
The PPM/GPS Viewer screen is displayed with a File Open Path Selection screen listing
all the files with extension 'TXT' on the Application Data folder. You can select one of
those but you can also change of folder and select one file from there.
It is the survey grid file where the readings will be reviewed.
After pushing OK button, you get this screen.
If the 'Fast Review' is checked, the whole grid file is read and displayed in one
shot. If it is un-checked, each reading is displayed and plotted. It is possible to pause
and resume the plotting with the 'Pause/Run' button.
If the file was not captured in GPS mode, the viewer screen will appear as an horizontal
PPM reading plot.
In pause or at the end of the reading, the precise localization of specific readings
as described in the real-time session chapter will also be active.
Clicking on any circle in the GPS track plot will show the corresponding point in the PPM
plot with an horizontal black line and will display the values of the UTC, the
latitude/longitude and Field Gradient there.
Panning of the GPS plot is executed by pressing the left mouse button, move the mouse
cursor in the required direction and releasing the button.
Zooming In/Out is by pressing the right mouse button to popup a context menu. You press
the button to zoom in while the mouse cursor is located where you want to see more details.
zoom
Clicking on any circle in the point in the PPM plot will show the corresponding GPS track
circle with an large black cross.
The 'Replay Grid' menu will combine the existing plot with the plot of a newly selected
file. The 'Clear Plot' menu will clear the plot(s).
To generate a KML file with the currently displayed GPS track and its optional
Waypoints, click on the 'KML' menu and select the KML/Load' menu of the popped-up
dialog.
To Read an existing KML file, click on the 'KML' menu and select the 'KML/Load ' menu
of the pop-up dialog. This KML could have been created from the PPM Utility program or
from Google Earth. In the latter case, it is possible to draw a Google Earth 'Placemark'
(in our terminology, a Waypoint) or a 'Path'.
If a path has been drawn on this KML file, it will be displayed as a blue trace.
If a placemark has been generated on this KML file, it will be displayed as a small blue cross.
In all cases, 'Quit' menu will close this screen. In GPS mode, the vertical PPM plot has a Scroll bar. This scrolls through a long survey file and only show a segment on it on the PPM plot. Clicking on any point of the GPS plot or any point on the PPM reading plot with the RIGHT
mouse button will pop-up a context menu giving the choice to generate a new Waypoint or to
start a GPS tracking process. If the 'Create WP' item is selected, the program
generates a Waypoint whose description can be given in the following popup dialog:
You can list all the current waypoints by clicking on the ''KML' menu. The following dialog pops-up. When you select one waypoint line, the corresponding GPS fix is displayed on the GPS plot with a Brown cross. If you click on any of those brown crosses, the corresponding WP will be selected on the item list.
After selecting one item in the list, if you click on it with the RIGHT mouse button, it
will start the GPS Track process, you will see the GPS Tracking screen popping up.
You can delete waypoints or edit their description.
The 'Measure' menu allows to measure the distance and the azimuth between two
selected points on the GPS plot.
You click on that button of the GPS Tracking window. Then, you push the left mouse
button down on the first point and go to the second point with the mouse button left
down. The GPS tracking window constantly updates the distance and azimuth between the
two points. When you release the mouse button and push on it on another point, this starts
a new measurement.
Stop the Ruler process by pushing on the 'Stop Measure' button on the GPS
Tracking window. You can automatically generate a survey route made of a number of parallel survey lines
starting from a first Route point.
First, click right mouse button on the point of the GPS plot where you want the survey
route to begin and generate a 'Route Segment'. This will appear as a first entry in the
combo box of the GPS Tracking window.
With a Route segment selected on the combo box, you can generate a survey grid by
selecting the 'Create Grid' menu
This is the survey grid generated from these parameters.
During the survey process, while the GPS tracking is active, if the distance to Target decreases to less than 10m (30ft), then the next route segment on the list is automatically selected and the GPS tracking is now directed to this end of this segment.
Each corner of the grid is a Waypoint which can then be used as a target for the
GPS Tracking process. This route segment list can be stored on disk with the
'KML/KML/Create KML' menu. This is how the Google Earth program shows this
KML file and its waypoints when loaded in it.
When reviewing a grid file associated with a KML file where there were already waypoints
recorded, these are loaded with the grid file to be reviewed.
10. Option of External GPS connected on the PC
The external GPS should generate a standard NMEA data stream at 4800 bauds.
The serial port connected to the USB or Bluetooth can be set on the PC from the
peripheral configuration to any COM port number LESS THAN COM10.
The PC program will discover the correct port number when being started IF the
system parameter $GP is Y. It just listens to every ports from 1 to 9 until it detects a
valid NEMA sentence.
On the Edit parameter window, it is set by the "GPS on PC" checkmark.
- If the GPS fixes have to be captured from the NMEA stream, the 'Op mode'
should be set to 'S'tatic and the 'GPS Option' should be set to 'N'one.
- If the NMEA stream comes from a Sonar, you have the choice to
- only capture the depth data from the Sonar (from its $INDPT
sentences) : the GPS Option should then be set to 'N'one and the 'Op
mode' set to 'S'tatic
- or also capture the GPS fixes from its stream : the GPS Option should then
be set to 'Y'es and the Op mode set to 'GPS' .
After this, you save to PC. The PPM will be automatically rebooted and the PC program will
terminate. You will just need to restart it.
11. Geo Referencing a Geographical or Nautical MAP
Select the 'Tools.../GEOREF' menu of the Main Window to enter the Geo-referencing
mode.
This mode of operation allows you to prepare any type of picture file showing a MAP or
satellite view to be used as background of the GPS plot. This mode displays the following
window after pushing on the 'Load Mapping' button for an already mapped picture file and
pushing on the 'Calculate' button.
Three waypoints of known GPS coordinates have been defined on that map. Each pair of GPS
coordinates is entered and the corresponding point is selected with the mouse of the
displayed picture. This generates the corresponding XY coordinates on the map. You see on
the following picture the three waypoints circled in white, blue and red.
Panning is made by pushing on the left mouse button and move it in the requested direction
and length.
Zooming in or out is made by pushing on the right mouse button at a given spot of the map. A
pop-up menu appears with the two choice zoom in and zoom out
To create a new Mapping, you click on the 'Create Mapping' button. This will display the
following window and will ask to select an existing picture file with extension JPG or PNG.
This particular picture was a screen dump from Google Earth.
Three specific waypoints were defined with their GPS Coordinates.
The first radio button is selected, the GPS coordinates entered in the Longitude
and Latitude data entry fields and the corresponding point is clicked with the LEFT
button of the mouse. This will generate the corresponding XY coordinates on the
screen. Apply the same procedure for the other two points and, finally push on the
'Calculate' button. This will draw a large red cross over the screen (it must be
orthogonal if the point definitions were correct).
Then, Push on the SAVE button to save the Mapping parameters in a file whose name is the
same as the picture file and extension is '.JGW'. The folder is the same as the picture
file.
This is how the end result looks on screen:
The geo-referenced map files can then be used as background image during a real time
survey session or a grid replay session.
Before starting the session, select the 'MAP/Load' menu in the Viewer screen and
select the mapped picture file. It will directly be displayed on the GPS plot area. Now,
start a session or replay an existing grid file and all the GPS plots will be displayed over
the MAP image. The background image will be panned/zoomed in parallel with the GPS plot.
If you select the plot mode 'CAP', the latest reading will be displayed at the center of
the PC screen and will rotate the whole screen (map and GPS plot) to stay with the nose of
the boat pointing toward the North direction.
This is an example of this screen after Zooming:
12. Saving/Restoring Background
As described before, a Geo-referenced Map can be used as background screen for
later real-time or reviewed sessions.
It is also possible to build custom background screens by combining an optional Map with
previously captured sessions and an optional KML file containing a list of Waypoints.
First, you optionally load a Map, you load one or several grid files and an optional KML file.
You can then add more waypoints or delete some followed by a KML save operation in a
specified KML file name.
Then, push 'Save Background' on the Session menu. It will ask for a file name and it will
generate an ASCI-coded file with extension .BKD.
When you need to use this background file as background screen, push on the 'Restore
Background' on the Session or the Map menu.
The Optional Map and KML files will be loaded followed by all the PPM information which
were present when the background as created.
13. Creating a GRID file
A GPS-based session can be converted into a Surfer-compatible GRID file if the GPS
tracks have been made as a more or less parallel survey lines as a total polygon-like shape as
demonstrated hereafter.
The system will interpolate the existing GPS points as a regularly-spaced grid with 5
points per meter (by default but it is possible to override this with a different value),
then save the resulting grid as the same file name and folder as the survey file but with an
extension .GRD.
The grid will be displayed in a new window as hereafter with a color scale showing positive
gradients as hot colors from green up to red and negative gradients as cold colors from
green down to blue and black.
The maximum and minimum Z values are displayed and could be modified later to limit the
extent of the color scale. The colors of the scale are regularly spread between the
average Z value and the current min/max values.
The generated grid file can be loaded by Surfer or by the PPM Utility program (Load Grid menu in this window).
A grid file generated by any version of Surfer and saved as SURFER 7 format type can
also be loaded by this program.
Moving the mouse over the grid displays the relative X and Y coordinates in meters and the
field gradient.
It is possible to draw the contours on the grid:
The displayed image can be freely panned and zoomed with the right mouse button and it can
be saved as a JPEG file.
The displayed grid can be used to manually or automatically mark some monopoles and dipoles
as potential targets.
A monopole is a region of the grid where the level is lower or higher than the average level.
A dipole is where a positive region is close to a corresponding negative region.
A monopole is marked by pushing on the right button and select the 'Create Monopole',
then click the left mouse button in the middle of a positive or negative region. This will
show its coordinates and its Z value in the right window. Then, you push on the 'Create'
button to confirm the target creation.
A Dipole is marked by pushing on the right button and select the 'Create Dipole', then
click the left mouse button in the middle of the first positive or negative region. This
will show its coordinates and its Z value in the right window. Then, you move the mouse
over the middle of the corresponding region of reverse color and you push on the 'Create'
button to confirm the target creation.
Targets on the list can then be deleted if necessary.
The list can be saved to an ASCII-coded TXT file and a file of targets can be
loaded.
the diameter of a target region or the distance between the two regions of a dipole can
be measured by pushing on the right mouse button and selecting the entry 'Measure'.
Keeping the left mouse button down from the start point to the end point will display the
distance between the two points in meters in the L text.
Targets can be automatically detected and marked.
First, you must decide what is the threshold of Z values to be detected. All targets
with a negative of positive Z values greater than this threshold will be considered and all
smaller Z values will be ignored.
Then, click on the right mouse button and select the 'Mark All Targets'
entry.
First, all the positive regions whose Z value is >= threshold will be detected and marked, then
all the negative regions will be marked, then, all detected positives monopoles will be taken
one at a time and the closest negative monopole will be found. If this negative monopole is at
a distance of less than 3 meters, the pair of monopoles is changed into a single dipole.
14. Merging Grid files into a single grid
The menu 'Merge Grids' allows to merge several distinct grids into a single one.
This is useful to get a general overview of a large area which had been surveyed in
several non-overlapping sessions.
For overlapping sessions, it is advised to load those survey files in the viewer at the
same time and generate a single grid from there. The resulting grid will be of much
better quality with that procedure than combining individual grids.
For merging grid files, you push to the 'OpenGrid(s)' button and select several grid
files from a disk directory. These grids should have been generated witht he same
resolution (points per meter). When confirming it, the grid files will be loaded one at a
time and, at the end, the resulting grid will be displayed on screen.
The parameters of the combined grid are calculated and displayed as well as the
parameters of the individual grid currently selected on the list of grid file names.
Selected grid(s) can be deleted from the list. When you want to see the new combined grid,
push to the 'Display Merged Grids' button.
When the result is satisfactory, you can save the combined grid as a new file.
15. PPM Survey Session Analysis Process
Domains of Application
PPM Surveys may be executed according to various types of procedures.
- When a very large area has to be surveyed to find potential targets at random, the
survey path is linear with large distances between contiguous survey lines. This is mostly
the case at sea when there is no previous indication of potential targets in a given area.
The best procedure in that case is to make almost parallel survey lines with a large
distance between them in order to cover a maximum of surface using a loose mesh of lines.
- When an area of ground or sea has been recognized by documents or by loose mesh surveys
to contain potential targets, the survey lines must then be defined using a dense mesh of
parallel lines. We then talk about 'Survey Grids'.
The survey lines can be defined based on topographical features and drawn as much parallel
as possible in order to completely fill the defined area with a dense mesh of PPM
readings.
The control of the survey path could be based on flags and lines physically drawn on the
ground or it can be based on GPS Fixes.
Linear Surveys
The analysis of linear-shaped surveys can be partly made in real-time by responding to
aural and visual feed-back given by the PPM System. When a potential target is detected,
its current location can be indicated by dropping a buoy at sea or a small flag on the ground
(another method is to use a spray of paint.
This first procedure is the only one applicable is there is no way to precisely return to
a given point of the survey line after the real-time session.
If the survey session has been controlled using a real-time coordinate recording system
like a GPS or any other physical system, this procedure can be complemented with a post-
process analysis. In this case, the PPM Utility program is used to review the survey files
and plot its results in order to detect potential targets which could not be detected in
real-time. The following screen dumps show clear targets (shipwrecks?) detected as alarge
dipoles during two distinct linear surveys at sea.
From this plot, it is then possible to generate a waypoint (see T1 and T2) using the popup
menu displayed with the right mouse button.
The list of Waypoints can be saved as a simple ASCII-coded file using the KML
editor.
This editor can also generate KML files to be displayed in Google Earth.
Grid-shaped Surveys
In order to detect all the potential targets within the limits of a given area, it is
necessary to define a dense mesh of parallel survey lines and make readings fast enough
over each lines
so that the distance between reading points is smaller than the radius of magnetic
field disturbance generated by expected target types. Looking for large shipwreck
remains does not require as dense mesh as looking for small UXO. Usually, the distance
between consecutive parallel survey lines at sea could be around 10 meters while it is 1
meter while looking for smaller underground targets.
The lines should be made as parallel as possible in order to cover the area as regularly as
possible without skipping any potential target.
The analysis of grid-shaped surveys can also be partly made in real-time by responding to
aural and visual feed-back given by the PPM System but their post-processing will usually
uncover many targets which were ignored in real-time because the field gradients
generated during each independent survey line were not sufficient when the target is
located between consecutive lines.
The post-processing of grid-based survey sessions is essentially made of an interpolation
of neighboring field values.
Multi-line survey grids
For survey sessions made as multiple parallel lines physically or virtually drawn on the ground,
each line has been referenced with a line coordinate (0 to L) but each reading value within a
line has not been referenced.
Based on the fact that the actual length of all the survey lines is known (thus, making
together a rectangular area), that the readings over a given line have been captured at
a fixed rate and the operator walking at a fixed (but unknown) pace, a first post-
processing will regularly spread the readings of each line and give them a point
coordinate (0 to P). This process is automatically started at the end of each session
made in the multi-line mode of operation of the PPM. It uses the 'row length'
parameter defined by the operator together with the numeric identification of the
session before starting this survey. It generates a new survey file with a name
starting with 'GG' instead of the usual 'GD' string. This 'GG' file can then be used by
the PPM Utility program to plot the survey session. This is an example of such a plot:
As you can see, there are some targets but the disturbances they generate are spread over several consecutive reading points and lines. In order to better individually emphasize each of them, we need to apply a 2D interpolation between neighboring points.
This is made by the 'SESSION/Make Grid' sub-menu.
The grid to be generated will be interpolated with a number of points per meter in the
two dimensions. This value is requested in the following dialog:
If there are some bad readings, these can be integrated or excluded from the results.
If integrated, they could be replaced by a choice of selected values:
0 : means that each bad reading will be replaced by the minimum gradient value of the whole
grid.
1 : means that each bad reading will be replaced by the last valid gradient value.
2 : means that each bad reading will be replaced by the average gradient value.
3 : means that the bad readings will be ignored.
This is the grid generated with 10 points per meter from the GG file displayed
before:
We can clearly see that there are a few targets generating either monopoles or dipoles.
The negative peaks are spots colored blue to black while positive peaks are from yellow, red
up to white. The average level of the grid is green.
The minimum gradient value of the whole grid is -173nT and its maximum is 137nT.
GPS-controlled survey grids
During the survey sessions made under control of a GPS system, each gradient reading value
is linked to its precise GPS fix. Thus, no more post-processing has to be executed
before making the interpolation process generating 2D grids.
This is such a survey session file as displayed in PPM Utility.
It is actually made over the same ground area as the previously described survey session
but under GPS control. In principle, the same targets should be visible in this plot as in the
previous one.
This is the grid generated with 10 points per meter from this file.
This is a perfect example of a large grid made with parallel lines under control of a GPS This is the corresponding grid.
Grid Analysis
Let's take for example the first simple grid made without GPS control.
It is clear that there are some targets detected by the survey.
Some of them (actually, most of the time) are 'Dipoles'. The real target is located just between a high peak (warm colors) and its corresponding low peak (cold colors). Here, we get two dipoles, one relatively large and one weaker one.
Some of them are 'Monopoles'. They just show a single positive or negative peak.
Here there are one positive and one negative Monopoles.
There are three methods to locate them:
1. Manually point and mark monopoles and dipoles by using the drop-down
menu activated by the right mouse button.
For a monopole, you first activate the monopole marking state, then, you click on the tip of the monopole and push on the 'Create' button located over the target list.
For a dipole, you first activate the dipole marking state, then, you push the left button
on one peak of the dipole, while keeping it pushed, you then move the mouse cursor to the
other peak of the dipole and release the button. Finally, you click on the 'Create' button.
This is the result of manually marking a monopole and a dipole.
2. Automatic target detection process also activated by the right mouse button.
This is the result of such a process defined for targets generating field gradients higher or equal to 30nT (set by the value marked 'Threshold G').
Note that the target 3 is not really inside the survey area and thus, could be deleted
using the 'Delete' button after having selected it on the target list.
The target 9 is also a false hit.
The dipoles 0 and 2 could possibly be re-qualified as a monopoles by first deleting them
and then, manually recreate them as monopoles.
Note that the 'Threshold G' value should carefully be selected. If you set it too high, it
will skip some lower peaks and if you set it too low, it will generate a lot of false hits.
3. Automatic target detection activated by the 'Generate Targets menu.
This menu defines the first threshold value 'ThresholdG' using the absolute maximum value of the 'Z Limit High' and 'Low Limit Z' and marks targets using this threshold. If there are some, they are displayed and the dialogue (below) is displayed asking whether it is OK or to continue.
If asking to continue, the threshold is reduced by 10nT and the program retries using
the new threshold. If the answer is OK or EXIT, the process is stopped with the latest
targets found. This can continue until the last threshold 10nT. If the threshold is
decreased but the number of targets found is the same as in the previous phase, the
program jumps to the next phase without asking anything.
If you find that two monopoles have been marked closed to each other and with inverted
polarity, they make probably a dipole.
Select both lines on the multi-selection target list and push on the 'Convert to Dipole' button. The two monopoles will be converted into a single dipole.
In all cases, as soon as the list of targets is confirmed, you save it with the 'Save
Targets' button.
If you make some panning or zooming on the picture, the target markings are cleared. In
order to re-display them, push on the 'Refresh Targets' button.
The button 'Save Image' generates a PNG file and a KML file.
The button 'Save Targets' generates a file of targets in a format suitable to be reloaded later using the button 'Load Targets' as well as a file of Waypoints ready to be loaded using the sub-menu 'WPT/Load Wpt List' in the KML Editor.
It is a good idea to come back to the standard Viewer screen, load the waypoint file and
have a look at the spots they mark on the GPS Plot area. If some of them look like false
hits, it is still possible to remove them using the KML Editor.
It is also possible to insert some more at this level by using the right mouse button
context menu.
Let's look again at a previous grid:
The actual max/min limits of the field gradient are +56nT and -27nT.
Note that most of the surface of the grid looks quite flat (light green). The few large
peaks use the whole range of color scale.
If you want to see smaller disturbances, you can reduce the high and low Z limits.
This is the grid with limits of +20nT,-20nT: The larger positive peaks which were cut down become WHITE and the larger negative peaks which were cut down become BLACK.
The variations of field gradients around 0 are now much more visible on the color scale.
Note that this is not an extreme example but, let's say you get a single peak of 300nT on
a survey grid. You will only see that one and all the smaller ones will be hidden until you cut
down this large peak on the plot.
Note also that the reduction of the limits is only effective on the display, the
automatic target detection is not affected.
16. Upgrading Firmware The upgraded firmware versions are available as files with extension '.FWP' for
PPM firmware.
When receiving a new firmware file through EMail, you must first copy it on your SD
Card and make sure it is the only file with that extension on it. If there was any before,
delete it.
To upgrade the firmware of the PPM, you should push on the 'Firmware Download' menu on
the Main screen of the PPM Utility program. It will find the first file with extension
'.FWP' and load the flash of the PPM with it.
17. Audio Capture mode The PPM Utility program can also be used to capture and record the audio output from any type of geophysical instrument. It is sufficient to connect its audio output (usually, the loud speaker or the earphone jack connector) to the audio input of the PC or tablet. The program will use its audio board and drivers to measure and record the variations of frequencies and/or amplitudes of the audio signals about 5 times per second. Before starting an audio capture session, you should first select the mode in which the signals will be captured. The 'Connection Type' should be set to 'Audio Port' and one 'Audio Type' has to be selected among the following list:
- Amplitude Modulation This mode measures and records the amplitude of the signal 5 times per second as field gradient. - Count Periods This mode measures and records the count of times the amplitude of the signal is over a threshold defined as the first parameter. - Multiple Frequencies This mode is defined by two frequency threshold parameters. The frequencies between the two thresholds will generate positive gradients and frequencies over the second threshold will generate negative gradients - Frequency Modulation
This mode defines two frequency thresholds (F1 and F2) and an offset frequency (F3). For all signal with frequency F between the two thresholds, the field gradient is calculated as F - F3.