First, the navigation in the GPS files was checked. One file - L18F1 - had several navigation gaps. This file was split into 3 parts effectively eliminating the navigation gaps. The gaps would cause problems in processing of the data. Additionally, the navigation in the GPS files was inspected visually. This was done by quickly parsing the GPS text files into comma-delimited text files with a header line, and then viewing the files in ArcMap 9.2. The AWK scripts used to parse the navigation was awkhold.
awkhold:
BEGIN {
FS = ","
}
{
FS = ","
ARGC = 2
depth = -9999
temp = -9999
if (NR==1)
{
#printf("utctime, longitude, latitude, depth_m, temp_c, line\n")
}
if ($1=="$GPRMC")
{
utctime = $2
latdeg = substr($4,1,2)
latmin = substr($4,3,6)
declat = latdeg + (latmin/60)
londeg = substr($6,1,3)
lonmin = substr($6,4,6)
declon = -1 * (londeg + (lonmin/60))
if (NR==1) {
holddepth = -9999
holdtemp = -9999
}
else {
printf("%s, %9.6f, %9.6f, %5.1f, %5.1f, %s\n", holdutctime, >holddeclon, holddeclat, holddepth, holdtemp, ARGV[2])
}
holdutctime = utctime
holddeclon = declon
holddeclat = declat
holddepth = -9999
holdtemp = -9999
}
if ($1=="$SDDPT")
{
depthreal = $2
holddepth = depthreal
}
if ($1=="$SDMTW")
{
tempreal = $2
holdtemp = tempreal
}
}
END {
printf("%s, %9.6f, %9.6f, %5.1f, %5.1f, %s\n", holdutctime, holddeclon, holddeclat, >holddepth, holdtemp, ARGV[2])
}
This file was executed by a shell script to effectively batch process all the files in a single folder with the extension gps. The batch processor was dohold.
dohold:
files=`ls *.gps | cut -d. -f1`
for file in $files
do
awk -f awkhold $file.gps $file >> may14_09_gps.txt
done
Under Cygwin, all of the hold files were concatenated into a single comma-delimited text file and a header line added to the file. The header line added to the text file was: gpstime, longitude, latitude, depth_m, temp_c, line. Using ArcMap 9.2 - Tools - Add XY Data, the comma-delimited text file was added as an event theme to ArcMap. No erroneous points were detected.
