![]() | ![]() | ![]() | Real-time logging |
At present there are two variants of the implementation, that will probably be merged in the future. Any receiver sending data in the NMEA 0183
v2.0 standard format can be used with GPSMan and can use any of the two variants. This also applies to Garmin and Lowrance receivers. For the time being there is no support for real-time logging if the receiver is declared to be a Magellan .
Users of Lowrance receivers will want to use the variant for Lowrance. Users of Garmin-defined protocols, either the so-called Garmin protocol , or the Simple Text Output Protocol, should use the variant for Garmin.
Both variants implement some sort of simulator that can be helpful for tests and in getting acquainted with the interface before going to real-time usage.
GPSMan will work with the variant corresponding to the receiver brand selected in the options menu. After changing this option the program must be restarted because different code has to be loaded.
This variant was designed and implemented by Brian Baulch (baulchb_at_hotkey.net.au) who has prepared a description of it.
The file exerciser.tcl
used for
simulation
by this variant can
be found in the util
directory. It must be edited for configuration
before use.
This variant implements:
supported by this variant are the following:
GRMN/GRMN
or Garmin
) protocol,
Text Out
), and
The receiver must be
configured to use one of these protocols. On
Garmin receivers this is done in the receiver's Interface
display under Setup
. Not all Garmin receivers support the first
two, in which case NMEA 0183 should be selected and the variant for
the Lowrance may also be used. If the selected protocol is not
supported, either GPSMan knows about that and issues a warning, or
there will be no information captured by GPSMan.
Facts that may help in choosing among the available protocols:
is done in the GPSMan's receiver window using the Protocol
menu, or the entry with this name of the GPS Receiver
menu.
Note that there is an option that defines the default protocol
to be used.
If GPSMan was invoked by using the start travel
command the protocol will be either the default in the
preferences file or the protocol given by the -prot command
option.
Two other entries in these menus start simulators of logging data that will be helpful in getting acquainted with the interface before real-time usage:
simulator
generates random (and somewhat inconsistent) data;
driving simulator
provides an interface for the user to
"drive" (starting from a waypoint) and in this way generate
logging data.
A simulator will be switched off only when a different protocol is selected.
Controlling the real-time loggingis done with the three
buttons Get Log
(or Stop
), Record
and
Animation
in the receiver window, or the corresponding
entries of the receiver menu under Real-time track log
. The
first starts and stops the input of logging information, the second
launches a window that records that information, and the third
starts the
animation
on the map. These buttons/entries can be actuated independently of each other, but it is obvious that the recording or the animation cannot start or go on if the input has not started or has been stopped. In this way the user may select when to record or when to have the animation. The recording window or the animation control window must be used to stop recording or the animation, respectively.
command
the animation is started unless the connection to the receiver could not be established.The control buttons in the recording window and in the animation control window affect only the recording and the animation, respectively, except in what concerns the logging time interval which is the same for the recording and the animation. The minimum value for the time interval depends on the rate at which the receiver sends information. The initial value for it is 2 seconds. The recording window and the animation control window will appear only after the first valid logging information is received, and this means at least 2 seconds from the clicking on the buttons/entries.
command
the time interval can be given as the last argument to the command.shows several columns with the logging information. These are, from left to right:
Columns for which there is no information for the very first fix
will be hidden automatically. The title of a column is a button
that hides the column. This will be wanted for columns that are not
being used or needed. The information in a hidden column is not lost
and is updated. At any time a hidden column can be shown again by
selecting its name from the Show
menu.
The Restart
button will destroy all the recorded information
and restart recording.
The entries in the Save
menu save as
text the contents of the columns either in a one-shot fashion
(Existing log
), or writing the current contents and writing each
new information when it comes up (continuously
). In the latter
case, the file will be closed when this menu entry is deselected or
when real-time logging is stopped.
The text obtained with this menu cannot be re-loaded by GPSMan.
To save the information in a format readable by GPSMan the
Make TR
button should be clicked to create a track, which can
then be saved and loaded in the normal way.
works as the animation for a track described above. The main difference is in the scale that instead of setting the animation speed sets the logging interval .
For the time being there is no automatic loading of background images, a feature present in the variant for the Lowrance.
The travel/navigationChange
menu (referred to as the menu in the
remainder of this subsection) to control travelling/navigation and
giving access to the receiver menu.
interface is at the sole risk of the user. In particular, the use of a laptop computer while driving alone is extremely dangerous. The user may also want to read the safety alert from the United States Coast Guard regarding the use of GPS equipment in boats.
command
travelling is started unless the connection to the receiver could not be established.The following information from the real-time log can be shown when travelling:
TRK
, true track, current bearing (COG, course over
ground, CMG, course made good, track made good), true North,
Other information only available when navigating:
CTS
, course to steer,
TRK
/CTS
indicator, with an external compass ring
(current track pointing up) and a CTS arrow,
TRN
, turn (difference between course to steer and true
track),
TRN
arrow indicator,
To
, current destination (when following a route or
track, next point in it),
From
, previous point in route or track,
ETA
, expected time of arrival at current destination,
ETE
, expected time in route to current destination,
VMG
, velocity made good (velocity along line from
starting/previous point to current destination), in user units,
XTK
, cross-track error (distance from current position
to line from starting/previous point to current destination), in
user units.
Navigation is started from the menu by selecting an objective which can be forgotten (navigation stops), suspended (navigation displays are frozen) and resumed.
Navigation to a point is made along a line of constant bearing with no drift (wind or stream effects) taken into account. This means that the transport velocity is assumed to be null and that CTS (the course to steer) is taken to be the bearing to the point. Computations use the so-called plane-sailing formulas that are commonly accepted as valid for distances up to 600 nautical miles [Gardner and Creelman, 1965], [Moore, 1964], [Macfarlane, 1963]. A point is arrived at when the distance to it is less than a user defined arrival distance.
Navigation along a route or track can be configured to be made:
At any moment the user can force a change to the next goal from the travel menu.
Following a route or track in an approximate way is implemented by
considering only the current position and the next two points (the
current destination and the point after it if there is one) because of
efficiency issues. This means that navigation will be blind to all
other points in the route or track even when the current position is
closer to any of them than to the next two points. The criterion for
changing the goal has a looseness parameter that can be changed from
the menu. When a change to the next goal is about to be made a second
CTS arrow (in a different colour) will be shown in the
TRK
/CTS
indicator giving the bearing to it.
Tracks will be simplified to the maximum number of waypoints allowed in a route before being followed in an approximate way. In this case, numbers identifying track points will be preceded by an asterisk ("*") indicating that the numbers are different from those in the track.
Going back is implemented as following exactly the travelling log in reverse. This log is started when travelling begins and cleared only when restarting travelling, upon user confirmation. As a copy of it is used in going back, such a navigation will not be affected by clearing it.
Warnings will be issued as messages at the left upper corner of the map. Different colours are used for different priorities. User warnings can also be issued after configuration from the menu, and warnings (except those standing for danger) can be disabled without loosing the configuration. In case a warning is issued when another one is still being displayed it will either replace the previous one or be discarded depending on their relative priorities. There are the following classes of priority, in decreasing order:
owner | usage | |
important | GPSMan | possibly dangerous situations |
high | user | |
medium | user | |
normal | GPSMan | arrivals, errors |
low | user | |
info | GPSMan | other information |
when | needs | |
proximity to WP | approaching | WP, distance (user units) |
leaving (anchor) | WP, distance (user units) | |
speed | in excess | limit (user units) |
vertical speed | out of range | minimun (may be <0), maximum (m/s) |
turn | in excess | limit (degrees in -180 to 180) |
cross-track error | in excess | limit (user units) |
mig_at_ncc.up.pt
, DCC-FC & LIACC,
Universidade do Porto, 2004![]() | ![]() | ![]() | Real-time logging |