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Interpolation with islands

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#1
NeverEasy

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Hi again!

I have point data located in the archipelago with info about the depth, among other things. Since it's in the archipelago, there are of course a lot of islands (represented as polygons) in the area. What would be a good way of taking into account the islands when interpolating the depth? I read somewhere that someone had made points, with a depth of zero, around and within the islands to represent them. This would be fine, but since there are a lot of islands it would take some time to draw all the points manually. Like I mentioned in my previous post, I have access to Manifold and ArcGIS (with 3D and spatial analyst). I am not able to download any new extensions.

Thanks!

#2
Hans van der Maarel

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I have point data located in the archipelago with info about the depth, among other things. Since it's in the archipelago, there are of course a lot of islands (represented as polygons) in the area. What would be a good way of taking into account the islands when interpolating the depth? I read somewhere that someone had made points, with a depth of zero, around and within the islands to represent them. This would be fine, but since there are a lot of islands it would take some time to draw all the points manually. Like I mentioned in my previous post, I have access to Manifold and ArcGIS (with 3D and spatial analyst). I am not able to download any new extensions.


Not sure on how exactly to do this in Manifold or Arc, but if you add the island polygons in as contour lines with elevation 0 you can use those and your depth soundings to calculate a bathymetry model. I think the results of this would even be a tad more accuracte than when you use points along the shorelines.
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#3
dsl

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I know Arc has a tool to convert feature vertices to points. I'm pretty sure manifold does as well. You could then add a depth field set at 0 and merge it with your depth points...presumably these have the same field name for depth. Otherwise, you might look into the barrier option when you do your interpolation. That should treat your islands as excluded areas.

Hope that helps.

Cheers,
David

#4
BCowper

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In Manifold I would create a new Drawing with the same projection as your Points drawing, add Lines or Areas representing the islands, open the Drawing's Table and add an elevation column (make sure the Column is the same format as your elevation column in your Points Drawing), select all records in the table and enter 0 into this column, all island records will now have 0 elevation assigned. Open up the islands Drawing window, using the Transform toolbar, select All Objects > Points > Apply. Point objects for each island vertex will now be created and will inherit the 0 elevation value, you can now copy and paste the Island Point objects into the original Points Drawing.

Current software used: ArcInfo 10.1 (Spatial and 3D Anaylst), Manifold 8.0 Ultimate x64, AutoCAD Civil/Map 3D 2011 x64.





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