awk and NMEA strings

rleal · #1 (**permalink**) 07-07-2008

Hi all:

I have a file with NMEA sentences of the type:

Code:

$GPVTG,012.0,T,,M,00.0,N,,K*7D
$GPRMC,180541,A,3631.874,N,00617.423,W,00.0,004.0,210608,,*36
$SDDBT,,f,,M,,F*28
$GPGLL,3631.874,N,00617.423,W,180542,A*3B
$GPVTG,009.0,T,,M,00.0,N,,K*77
$GPVTG,019.0,T,,M,00.0,N,,K*76
$GPRMC,180546,A,3631.874,N,00617.423,W,00.0,019.0,210608,,*3D
$SDDBT,,f,,M,,F*28
$GPGLL,3631.874,N,00617.423,W,180548,A*31
$GPVTG,012.0,T,,M,00.0,N,,K*7D
$GPRMC,180551,A,3631.874,N,00617.423,W,00.0,004.0,210608,,*37
$GPVTG,004.0,T,,M,00.0,N,,K*7A
$SDDBT,,f,,M,,F*28
$GPGLL,3631.874,N,00617.423,W,180554,A*3C
$GPVTG,009.0,T,,M,00.0,N,,K*77
$GPRMC,180556,A,3631.874,N,00617.423,W,00.0,017.0,210608,,*32
$SDDBT,000016,f,00005,M,0002.7,F*01
$GPVTG,017.0,T,,M,00.0,N,,K*78
$GPGLL,3631.874,N,00617.423,W,180600,A*3E
$GPVTG,038.0,T,,M,00.0,N,,K*75
$GPRMC,180601,A,3631.874,N,00617.423,W,00.0,038.0,210608,,*3E
$SDDBT,000016,f,00005,M,0002.7,F*01

$GPRMC for position and time, $SDDBT for depth. All sentences are sequential in time.

I can extract position and time with awk, no problem:

Code:

gawk -F "," '$1=="$GPRMC" && $3 != "V" { print 20substr($10,5,2),substr($10,3,2),substr($10,1,2),substr($2,1,2),substr($2,3,2),substr($2,5,2),substr($6,1,3),substr($6,4),substr($4,1,2),substr($4,3)}' NMEAfile >output

and depth:

Code:

gawk -F "," '$1=="$SDDBT" && $4 !="" { print $4}' NMEAfile >output

I would like to combine position, time and depth into one single file, only if depth is true (note that sometimes $SDDBT,,f,,M,,F*28 -no depth info-). That is, if depth is true then use the position from the previous occurrence of $GPRMC and combine them into a single line. Sure that's possible with awk/gawk, but don't know how to do it.

Thanks in advance,

r.-

zaxxon · #2 (**permalink**) 07-07-2008

I am not sure if I got it right and what your wanted output should like, but to be sure you don't get the lines with "no depth info", why not just append that expression the the awk you already have like

Code:

... && !/no depth info/

You used such stuff in your awk line already so.. maybe I just did not understand

An output example might make it much easier to understand, ty.

rleal · #3 (**permalink**) 07-07-2008

Sorry for the misunderstanding. I cannot add your suggestion because each sentence is written in a different line. The desired output from

Code:

 $GPRMC,180541,A,3631.874,N,00617.423,W,00.0,004.0,210608,,*36
$SDDBT,,f,,M,,F*28
$GPGLL,3631.874,N,00617.423,W,180542,A*3B
$GPVTG,009.0,T,,M,00.0,N,,K*77
$GPVTG,019.0,T,,M,00.0,N,,K*76
$GPRMC,180546,A,3631.874,N,00617.423,W,00.0,019.0,210608,,*3D
$SDDBT,,f,,M,,F*28
$GPGLL,3631.874,N,00617.423,W,180548,A*31
$GPVTG,012.0,T,,M,00.0,N,,K*7D
$GPRMC,180551,A,3631.874,N,00617.423,W,00.0,004.0,210608,,*37
$GPVTG,004.0,T,,M,00.0,N,,K*7A
$SDDBT,,f,,M,,F*28
$GPGLL,3631.874,N,00617.423,W,180554,A*3C
$GPVTG,009.0,T,,M,00.0,N,,K*77
$GPRMC,180556,A,3631.874,N,00617.423,W,00.0,017.0,210608,,*32
$SDDBT,000016,f,00005,M,0002.7,F*01
$GPVTG,017.0,T,,M,00.0,N,,K*78

would be

Code:

 
210608 180556 36 31.874 00617.423 00005

What it should do is get the depth (if not empty) and grab the corresponding lat,lon,time from the immediately previous $GPRMC line. In this example the first 3 $SDDBT sentences have no depth info (with comma as separators ,, means empty value).

best regs,

r.-

radoulov · #4 (**permalink**) 07-07-2008

Code:

awk -F,>ouput '/GPRMC/ {
  _ = $(NF-2) s $2 s substr($4, 1, 2) s substr($4, 3) s $6 
}
/SDDBT/ && $2 { print _, $4 }
' s=" " NMEAfile

And if SDDBT always follows immediately GPRMC,
this should be sufficient:

Code:

awk -F,>ouput '/SDDBT/ && $2 { print _, $4 }
{ _ = $(NF-2) s $2 s substr($4, 1, 2) s substr($4, 3) s $6 }
' s=" " NMEAfile

darius2 · #5 (**permalink**) 01-01-2009

Quote:

Originally Posted by radoulov

Code:

awk -F,>ouput '/GPRMC/ {
  _ = $(NF-2) s $2 s substr($4, 1, 2) s substr($4, 3) s $6 
}
/SDDBT/ && $2 { print _, $4 }
' s=" " NMEAfile

And if SDDBT always follows immediately GPRMC,
this should be sufficient:

Code:

awk -F,>ouput '/SDDBT/ && $2 { print _, $4 }
{ _ = $(NF-2) s $2 s substr($4, 1, 2) s substr($4, 3) s $6 }
' s=" " NMEAfile

Hi,

I have the same problem with NMEA sentences, streamed on-line to stadout, in terminal session, running gpsd or gpspipe.
I would like to learn how to pipe NMEA into awk script code
to get selected gps data like long, lat, speed, time
from selected NMEA sentences, for use in another pipelined application.

First I need to create NMEA > AWK > output pipe

Got a nice example from
Info: (gawk.info) Getline/Pipe
awk '{
if ($1 == "@execute") {
tmp = substr($0, 10)
while ((tmp | getline) > 0)
print
close(tmp)
} else
print
}'
and another awk manual with examples
The GAWK Manual - Reading Input Files

Got another example

I am trying to create a pipeline which prints every word on a new line, then sorts them and applies uniq -c to it!
{c=split($0, s); for(n=1; n<=c; ++n) print s[n] | "sort" | "uinq -c"}

answer

fmt -1 filename|sed 's/[ ,.":;!]//g'|sort -f|uniq -ci

What is a way to create a pipeline for a data stream generated by gpsd, gpspipe ?

gpsd > filename |sed ..
gpsd | getline .....

Or just please refer me to a nice place.

Thanks.
Happy New Year

Darius

summer_cherry · #6 (**permalink**) 01-02-2009

Hi not very sure about your detail logic, but below perl script may help you some

Code:

#! /usr/bin/perl
open FH,"<a.txt";
while(<FH>){
	my @tmp=split(",",$_);
	if($tmp[0] eq "\$GPRMC"){
		$tmp=$tmp[9]."-".$tmp[1];
	}
	if($tmp[0] eq "\$SDDBT"){
		my @arr=split(",",$_);
		print $tmp.":".$arr[3]."\n" if($arr[3] ne "");
	}
}
close FH;

rleal · #7 (**permalink**) 07-07-2008

Yes, that one did it!! Thanks a lot,

r.-

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