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Hi everyone,

I have some survey data of different cross sections along the river, if I can interpolate these data to the whole river, then I can get more realistic river shape or bathymetry data to run telemac2D and get more accurate water depth results.

However, how can I use the data I have to interpolate to the whole river?

Any help will be appreciated!

Best regards!
Yajuan

Sorry, maybe I didn't describe my question clearly, I want to interpolate into the DEM data using the surveyed cross sections. Other details are described above.

Hi Yajuan,

You can use the 2Dinterpolator in BlueKenue.

First, you can draw a closed line to define the boundary of your interpolation. You have then to create a new 2dinterpolator, drag your boundary as constraint outline and add the data you want to interpolate (cross profiles).

You can chose between different option, nearest neigbour, IDW or linear.

After that, you just have to select your DEM (wich is suppose to be a regular grid) and to use the map object tool. BK will map the result of the interpolator (that cannot be vizualised) onto your DEM.

You will have to make sure that your interpolation is correct...

Try this and ask again if you need help to get a good transition between your bathymetric data and your DEM...

Hope this helps,

Dear abernard,

Thank you for your quick reply.
Should the cross profile data be in point format? Because I used the 2D interpolator tool in BK before, I remember the data dragged into the 2D interpolator is point data. I will have a try, if success, I will tell you here.

Best regards!
Yajuan

Hi,

A word of warning:
Interpolating bathymetry to a mesh from cross-section data is a bit tricky as the sample spacing along the channel is usually much greater than across the channel. The Blue Kenue interpolator is intended to work with more or less isotropic data. Be sure to carefully check the resulting bathymetry.

1. The interpolator accepts lineSets (i2s or i3s) and pointSets
2. The constraint outline is not required. It is used only if you wish to apply the interpolated data to a portion of your mesh.

Martin

Hi!

Interesting topic, but I don't understand exactly what can be done with the 2D interpolator (I did not find information in the user manual).

I would like to know if it can be used to interpolate bathymetry along a natural channel from a set of cross sections (in xyz format for example). And if yes, what is the method to follow?

Any information would be much appreciated!

Thanks in advance,
PL

The interpolator hasn't made its way into the reference manual yet.

So here is the short version:

The interpolator simply provides a "virtual surface" to the "Map Object" function.

To use the interpolator.
1. File->New->2D Interpolator…
2. In the workspace drag any number of pointsets, 2D or 3D linesets onto the Interpolator object. You can use grids or meshes as source data by first saving them as pointsets.
3. Open the properties dialog for the interpolator
4. Choose the interpolation method (Linear, Inverse Distance or Nearest Neighbour)
5. Optionally supply a closed polygon to constrain the interpolation.
6. Optionally supply a Max Search Distance to constrain the interpolator.
7. Select your mesh in the WorkSpace to make it the current object.
8. “Tools->Map Object…” and select the Interpolator object as the source data when prompted.

NOTES:
- The Max Search Distance is self explanatory.
- The Linear algorithm triangulates the source data and then uses a linear interpolation from the triangles.
- The Nearest neighbour algorithm simply takes the value from the closest source data point.
- The Inverse distance algorithm finds the closest points in each of the 4 quadrants (subject to the Max Search Dist)
- The Inverse distance interpolation algorithm has been highly optimized. Interpolating depths to a mesh with over 200,000 nodes from almost 11 million points takes about 32 seconds.
- LineSets supplied to the interpolator are resampled automatically depending on the resolution of the target grid or mesh.

Dear abernard and Martin,

Thank you for your help. I have tried the method you told me before ,however, I didn't do it successfully.

I did it like this:

1. I created a new 2D interpolator and drag my cross section survey data(pointsets) to it
2. Open my dem data(bil format),
3. Selected DEM data-->tools-->map object, but the map object is gray, that means I cann't use map object function to interpolate my survey data to the DEM data.

The attached files are the error I met.

Is something wrong with my process?

Any help will be appreciated!

yajuan

Hi Yajuan,

For reasons long forgotten/no longer valid, editing/modifying BIL objects was/is forbidden. This includes mapping objects. Sigh...

The solution to your problem is to save the BIL object to a r2s file, load it and you'll be good to go.

My apologies... Martin

Dear Martin,

Thank you very much for your help.

I tried the suggestion you provided, and saved the bil format to r2s format, reloaded to BK, and do the interpolation again, however, there is a windows prompt appears, saying there is no suitable objects are available for mapping. In fact, I have created a 2D interpolator and drag my survey data(pointsets) into it.

Am I wrong somewhere? the attached file is the error I met.

Any help will be appreciated!

yajuan