NME Files - for recording GPS data
Updated 1630 Thursday 22nd September 2005
An NME file is a text file with extention .NME used by GPSS for the recording, playback and analysis of data received from the GPS.
This can be data from a directly connected GPS, when GPS is used in it's simplest navigation mode, or data from a GPS data-logger or remote tracking product, as explained on the AVL page.
In recent years GPSS has extended the NME system to record and playback other information such as operator actions at keyboard or mouse.
You can make GPSS record the GPS data arriving from the GPS receiver by hitting the % key. GPSS will display a message like "Recording GPS data to AAAAA001.NME" on the white speech bar at bottom of screen.
This file can then be played back, plotted or analysed with the GPSS Control-A Facilities such as REPLAY, PLOT and DRAW.
Here is some typical data from a NME file:
$GPRMC,131332,A,1548.075,S,04750.871,W,032.0,056.2,040300,019.1,W*66
You don't need to understand it - GPSS will do that - but you can see it is text, starting $GP, and you can probably recognise information in it such as Latitude-Longitude, time, date, speed and direction.
This is typical of what you will see in an NME file opened with a text editor such as Windows Notepad or Wordpad.
Your first introduction to NME files may be Robin asking you to send 5 lines from AAAAA001.NME (or whatever filename used), recorded with % key. This is probably just Robin wanting proof that you do have a GPS, and have it working correctly with GPSS. Only a few seconds of data is needed to give Robin the 5 lines - if he asks for it. Please do not attach this as a seperate file: just paste the text (lines starting $GP) into your e-mail message.
But NME files are also useful to track down and solve problems - Robin can see from the data if the format is "standard NMEA" and if it is not, can probably suggest a "work-around". They are also very useful to checkout the accuracy of new mapping - particularly street level mapping in countries where calibrated mapping is not already available. Robin often asks contacts to record NME files on agreed routes, so he can test new mapping before it is uploaded to www.gpss.co.uk.
Finally, they can simply be used as the means of recording a trip, for later playback and analysis on the maps, using GPSS.
The first time you hit the % key, GPSS will record GPS data into a file with the name AAAAA001.NME.
Next time, GPSS will record into AAAAA002.NME, then AAAAA003.NME, etc. i.e. GPSS records into the next free filename available.
The AAAAA is taken by GPSS from a text file NEWTRIP.CFG
You can give the NME file name a more suitable start based on your name. e.g. edit NEWTRIP.CFG and change AAAAA into JACKP or something suitable. Then GPSS will record into JACKP001.NME etc. It is reccomended that you keep this text to 5 characters. GPSS pads it out with numerics (e.g. 001) to 8 characters.
You can make the NME files recorded MUCH smaller (perhaps 5 x smaller) by making GPSS record only the data needed. Most GPS receivers, particularly Garmin, output the $GPRMC message which has all the important data of latitude-longitude, speed, direction of travel, time. The other NMEA messages are not needed. A file with only this $GPRMC data will be much smaller, will playback faster with GPSS Control-A, and will e-mail faster if you send it to others.
To make GPSS record ONLY the
$GPRMC message, make a text file with name GPSSLOG.CFG and with
$GPRMC
in the first line. The resulting NME file will be smaller and play
back faster with Control-A.
IMPORTANT: the presence of GPSSLOG.CFG will mean that GPSS may not
record other important information such as operator keystrokes
or mouse actions. You can make GPSS record %090/8 type DF bearings
by adding the % character.
%$GPRMC
See "recording operator keyboard and mouse actions" below.
Here is some data from a Garmin GPS without GPSSLOG.CFG:
$GPRMC,131332,A,1548.075,S,04750.871,W,032.0,056.2,040300,019.1,W*66
$GPRMB,A,,,,,,,,,,,,V*71
$GPGGA,131332,1548.074,S,04750.870,W,1,07,1.3,1060.7,M,-10.1,M,,*56
$GPGSA,A,3,,03,,14,15,21,,25,29,31,,,1.3,1.3,1.0*3C
$GPGSV,3,1,10,01,05,319,32,03,51,335,44,11,20,216,30,14,11,263,31*72
$GPGSV,3,2,10,15,47,186,45,21,22,136,38,22,07,357,35,25,38,043,44*77
$GPGSV,3,3,10,29,34,147,42,31,51,267,44,,,,,,,,*75
$PGRME,16.1,M,29.5,M,32.9,M*1E
$GPGLL,1548.072,S,04750.865,W,131333,A*25$PGRMZ,3477,f,3*2C
$PGRMM,WGS 84*06$GPBOD,,T,,M,,*47
$GPRMC,131338,A,1548.046,S,04750.825,W,031.0,055.6,040300,019.1,W*69
$GPRMB,A,,,,,,,,,,,,V*71
and here is the same data, but with GPSSLOG.CFG specifying only $GPRMC:
$GPRMC,131332,A,1548.075,S,04750.871,W,032.0,056.2,040300,019.1,W*66
$GPRMC,131338,A,1548.046,S,04750.825,W,031.0,055.6,040300,019.1,W*69
- a bit smaller eh ? :-)
If you do not have a Garmin GPS, check that the GPS data does include the $GPRMC message - it may not - and you would be in danger of GPSS not storing ANY data.
For these GPS receivers, you might make it record a different combination of NMEA messages, rejecting the rest.
e.g. making a NEWTRIP.CFG file with
$GPGLL$GPVTG
- to make GPSS record $GPGLL (position) and $GPVTG (velocity).
If you already have a BIG NME file, you can use ONLYRMC to reduce it down to only the required data. See below.
GPSS v5.95 introduced more extensive % recording and Ctrl-A REPLAY of operator actions such as typing on the keyboard and/or clicking with the mouse. This was intended to support things like replay of RDF foxhunt operations where important information is entered both from live RDF hardware, and the operator (as a passenger).
These are currently NOT recorded if a GPSSLOG.CFG file is present, but it is expected to rectify this in pre-release v5.96 of GPSS on the oldnew page.
Here are some typical recorded operator actions:
$GPRMC,152208.093,A,5123.8108,N,00039.5823,W,0.00,,220905,,*07
;MLL "SU 93316 67294"
;MLC
$GPRMC,152209.093,A,5123.8136,N,00039.5847,W,0.00,,220905,,*09
$GPRMC,152210.093,A,5123.8131,N,00039.5796,W,0.00,,220905,,*05
;KEY "Q"
The $GPRMC lines are data direct from the GPS.
The ;MLL gives the mouse position, in geographic coordinates, before MLC - a mouse left click putting the destination at this position.
The ;KEY records the Q (be quiet) key being hit.
This little DOS program copies a file of GPS data such as AAAAA001.NME, taking only the $GPRMC sentences, to make a much smaller file that is more suitable to e-mail to people. Just download ONLYRMC.EXE somewhere convenient such as \GPSS04. It is not compressed - so when you run it - it will run for real and ask you for the two files (e.g. input file: AAAAA001.NME output file: MYTRIP1.NME)
DOWNLOAD ONLYRMC.EXE (41,208 bytes)
If when running GPSS, you hit Control-A, an "Analysis" Form will appear, with buttons such as REPLAY, DRAW, PLOT, etc.
To replay a demonstration, as if you were in the car:
1. Hit Control-A to display the Form.
2. Click on the NME file wanted in the list of NME Files.
3. Click on REPLAY
4. Hit * key to restart the demonstration.
5. Do not touch keyboard or mouse until you wish
to stop or pause demonstration.
You can speed up the replay with ">" key, or slow down with "<" key, but this will require a restart with "*", because any real keyboard action, other than "*", will stop keyboard emulation.
DRAW will draw the NME file as lines, on whatever map you have on the screen. You can control colour of the lines.
PLOT will plot the NME file, as fast as it can, automatically changing map to follow the car.
You can use GPSS to make NME files (e.g. for a demonstration) by clicking on the GPSS screen, to "drive the car around the maps".
To switch this recording on you type on the keyboard:
`nmea
- followed by the Enter key.
You will find that left button mouse clicks then move the car (before the left mouse button would move the destination)
Each click will move the car to a new position, and change its direction of travel in that direction.
Each click will also append a new $GPRMC sentence into NEW.NME as if it had come from a GPS receiver.
These NME files can then be renamed and edited, to make a demonstration.
You can use NME files to demonstrate GPSS working, as if it was "on the road", by playing back a NME file.
GPSS has always done this automatically, if run without a GPS receiver connected, and not modified for remote tracking. i.e. when it says, "I'm not receiving any GPS data.. let me show you something I did earlier..." - followed by the Ascot map appearing.
This is done with a "demonstration" NME file in GPSS.NME.
Most of the mapping downloads include demonstration files. e.g. JAKARTA.NME
You can make your own NME Demonstration files, using a text editor to add extra commands, such as operator keystrokes (or voice commands) into the NME file.
If you look in a demonstration NME file, you will see extra lines which are not NMEA data starting $GP.
e.g. KEY 04 or KEY "W"
KEY 04 emulates the operator hitting Control-D (binary 4) to remove the Destination, and KEY "W" emulates the operator hitting W (or saying "where are we ?" with speech recognition)