Merging resistivity profile from a water survey

BriceLeComte

I have several profiles overlapping processed separately from a shallow underwater survey.

I can process each profile fine until I am merging the 2 profiles. I can merge the files no problem but then I can't process them both with a water layer.

Any idea what should I do or if it is possible due to varying water depth on the 2 profiles?

Cheers and thanks,

Brice

EricaVeglio

Hi Brice,

Before we troubleshoot I need a bit more detail on your workflow.

-Are you merging the raw .dat files using Res2DInv's built in Merge tool on the Data tab, or combining them a different way (ie. combining .dat files in a text editor)?

-Are these two+ segments of the same physical survey line (as in extended coverage or rolling survey) or two separate crossing lines?

-When you say the water depth varies between the two profiles, do you mean the seabed/riverbed/lake bottom depth varies along the line (Res2DInv handles this through the topography data) or that the water surface elevation itself was different between the two survey sessions (were they run at different tide levels or referenced to different benchmarks)?

I am thinking that the last option is the culprit here. Res2DInv's aquatic survey format only allows one constant "water surface elevation" value per file, so if your two source files have a different value, merging them won't reconcile this. If this happens to be the case, the fix is to tide-correct or re-reference both profiles' topography data to a single common vertical datum before merging, so that only one "water surface elevation" value applies across the whole merged line.

Let me know what you find and if this helped! We can continue to troubleshoot.

BriceLeComte

Hi Erica,

Thanks for that.

1)I am using the merge option but without keeping the original coordinates as it doesn't plot correctly…
2) 2 separate file processed individually first
3) 2 separate water depth

I can run the default inversion (no water layer) on the merged file but I can't run the same inversion used for the separate file with an average water depth for instance but it won't update the model grid when the merge file as any parameter for water depth or resistivity….

How can I make it so that we have the same inversion workflow using the average water depth on the merged file?

Best regards,

Brice

BriceLeComte

Note: I either get change the inversion settings (grid could not be loaded) when I work from the file with the edited files with topo and coordinates or file could not be loaded (edits done after measurements) when I edit the concatenated file with topo but not global coordinates to put a water depth (average value between the two) as the keep coordinates option just make a file of a single spread length….

EricaVeglio

Hi Brice,

Thanks for the extra detail. I want to make sure I am troubleshooting the exact issue rather than guessing from a description. Would it be okay to send over the following so I can try to reproduce it on my end?

1. The original individual .dat files (the ones that worked correctly on their own)
2. Your inversion settings (you can export the settings file or just list the parameters so I can match your workflow exactly)

Once I've got those, I'll run it through on my end, see if I get similar errors and we can figure out the best way to get the merged line working with the averaged water depth.

Thank you and I'll be sending you a private message for a secure data transfer!

BriceLeComte

Thanks Erica, it is much appreciated.

I haven't seen a direct email just yet so here is my email just in case brice.lecomte@scantech.ie