TIN polygon tags, or some other way to create polygons from a TIN or a point file???

[KateRamsden]

Hi,
I have a file of irregularly spaced points that represent water depth (0-21 m).  I'd like to create polygons that represent areas of water inundation, based on defined intervals (0, 1-2, 2-3, etc etc).  I have tried a couple of different methods but don't feel like I've found the best way yet.

I am very new to 3D analyst and haven't worked with TINs before.  It seems like there are some options for creating polygons from a TIN using 3D analyst but I just can't quite figure out what I'm getting wrong.  I created a TIN with my points and it appears to look good.  Using the TIN polygon Tag tool results in a single polygon that is the extent of the TIN, even though when I created my TIN I chose the water depth interval attribute as the Tag value field.  I know I'm probably just not understanding something about the tool itself but so far the help documentation hasn't revealed the missing link to me.  🙂

Following some other posts I've read on here, I've also created contours with my TIN, and used the feature to polygon tool in arc toolbox in the Data Management Toolbox (along with a polygon of the study area boundary).  I used the point file to label the resulting polygons with my water depth interval, except that sometimes my contours are more narrow than the spacing of my points and that results in false zero values for polygons which I don't like. 

Right now I am trying to interpolate my points into a raster file, using the water depth interval, and thought I would try to create polygons using Spatial Analyst.  It's taking a long time, though - perhaps my cell size is too small.  Is there a row/column size limit on rasters? 

Thanks, any input is appreciated! 
Kate

[JakubSisak]

Do you need to create the polygons or do you just want the areas between each isobath to be symbolized.  (see attached for visual)
In the TIN symbology add only the elevation and remove everything else, then choose "Classify" under the symbology tab. Under Method select Defined Interval and under interval size type in the desired interval (1 for 1 metre for example). After you OK choose a graduated  ramp, Dark Blue to light blue for example.
You can then create TIN Contours from the same TIN and overlay.  If you use the same interval as you did for symbolizing the TIN, the contours will match the symbology.

You can also do the same with a raster surface.

[KateRamsden]

Hi,
Thanks for the response - I wanted polygons so that I could easily calculate areas of inundation by my defined intervals, and clip them down further by floodplain reach breaks, etc.  Currently, though, I've been following your suggestion of classifying the data for display purposes.  I also converted the tin to a raster and I can estimate the areas of my intervals based on the cell size and count..... not very sophisticated, I suppose, but it works for me!  🙂

[TylerBragg]

Kate,
Another option other than TIN creation:  You could run a Natural Neighbor Interpolation (Spatial Analyst or 3D Analyst Toolbox) on your points.  This will give you a grid that represents your depth.  Then, you can either Reclassify the raster so that each value of your raster encompasses your depth range, then Contour from there, or you could generate contours straight from your grid (Contour Tool, 3D Analyst) based on your cell value and the countour interval you want. Not sure if this helps, but might be another route. 

Tyler

[KateRamsden]

Thanks, Tyler,
I did try that and that would have been my preferred method, but I ran into some problems with processing time and grid cell sizes.  I wanted to create a grid with 2 m cell sizes.  Interpolating the points directly into a raster via 3D Analyst using Nearest Neighbor would cause it to stall out and eventually crash, but interpolating from the TIN to a raster did not cause that problem.  If I chose a larger cell size, though, like 5 m, it worked without a problem.  So in the end, points to TIN to raster ended up working pretty well for my project.