Datum Change

Can anyone tell me of an easy way to change all of the ground elevation data in a Hec- Ras model by a set amount. I have an old model that I need to update due to a datum change.

Christopher Moss
cmoss@taylorengineering.com

Chris:

I don't know of a way to move everything at once. You can move each cross-section a fixed amount. Go to Geometry->Cross Section Editor->Options.

Regards,
Michael E. Fanning
Milone & MacBroom, Inc.

Chris,

A simple way is to open the Geometric Data window. Then select the cross section tab. Once the Cross Section Data window appears go to the following menu Options --> Adjust Elevations.... From here you can add or subtract to the existing elevations for that cross section.

Jonathan Looper, E.I.
Nordic Engineering
looperjp@yahoo.com

Keep in mind that the geometry files are simple text files. It should be a fairly simple procedure for someone in your organization with a little programming backgroud to write a quick script to scan through the geometry file and make the modifications you require. With 600 sections, it'd be worth
spending a little time automating the process.

Dear Christopher Moss :

Note that RiverCAD can do all of the cross-sections with a single command. Select Input | Ground Geometry | Adjust Geometry.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com

Here is a Perl script which raises all XS points by 2.2 feet. It should get you started even if you don't have Perl
expertise on hand.


# Raises or lowers all cross sections in a RAS geometry file
# by a fixed amount. Specify two command-line arguments: the existing
# geometry filename (input file) and a new filename (output file).

$delta = 2.2; # number of feet to raise

($IN,$OUT)=@ARGV;
open(IN) || die "$!";
open(OUT,">$OUT") || die "$!";

while($_=<IN>) {
if(/^#Sta/Elev=(.*)$/) {
print OUT;
$nOrds=$1;
for($i=0;$i<=int($nOrds/5);$i++) {
@points=split(/s+/,$_=<IN>);
foreach $sta (2,4,6,8,10) {
$points[$sta]+=$delta if $sta<=$#points;
}
for($ind=1;$ind<$#points;$ind+=2) {
printf OUT "%8.1f%8.1f", $points[$ind], $points[$ind+1];
}
printf OUT "
";
}
} else {
print OUT;
}
}

Many of you have suggested using the "Adjust Elevation" option available from the cross section data window. Thank you for your suggestion, but, I have 2 models with nearly 600 cross-sections. I was hoping for a way to globally change large numbers of cross-sections. I can't believe nobody has run into this problem using existing models and needing to update the datum. Again, thank you for your responses.