Contour Lines from Polygon

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06-12-2020 11:26 AM
PhillipKnobloch
New Contributor

Hello everyone,

I have a dataset showing groundwater tables as polygons. The attribute table contains a column with a range of water levels (for example "30.5 m - 31.0 m").

I am trying to label  the contours with the water level at their respective isolines. So far I only created columns containing the lower and upper bounds but I am lost when it comes to label placement.

Does anyone know how to accomplish this? Any help would be appreciated.  

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5 Replies
George_Thompson
Esri Frequent Contributor

Have you converted the polygons to lines? Polygon To Line—Data Management toolbox | Documentation 

Are you trying to label the "contour" as a polygon?

Can you show a screenshot?

--- George T.
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DavidPike
MVP Frequent Contributor

I would go with George Thompson‌ but take it a small step further and spatially join those lines and then use a field calculation to take the minimum value of the two fields and then the value after the dash. Also ensure the code doesn't hiccup on a line with no matching join, such as the outer line of the enclosing polygon.

It just takes a bit of python index slicing and .split() method etc.

Feature 1 - Join Field - 0-10m, 10-20m -->10m

PhillipKnobloch
New Contributor

Hey, thanks for taking a look at this.

I tried the conversion to lines but this resulted in loss of the elevation attributes. But even if I managed to keep those, since right now each contour line consists of the outlines of two polygons, wouldn't the conversion to lines result in 2 overlapping lines each containing different elevation values?

What I am trying to achieve is a regular contour map with values written on contour lines like this:

A topographic contour map of mound 1 at the Wright Memorial. The contour interval is 0.1 m. This contour map, and the other topographic maps here, have been prepared from the measurements supplied by Bret Ruby and a crew of surveyors from Hopewell Culture National Historical Park. There is a tree in the middle of this mound.  

what I have is this:

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DavidPike
MVP Frequent Contributor

It's disappointing the tool doesn't transfer attributes, but these can be restored with a table join afterwards if 'identify and store polygon neighbour information' is unchecked.

yes, 2 overlapping lines should be created if the checkbox is unticked. You can approach it wither way by retaining the neighbour information, but I think this is a more understandable workflow.

Spatial Join - Join the lines to themselves and each will get the height attributes of the intersecting line.

Afterwards field calculate a new field showing the values of both heights e.g !HOEHE! + ", " + "!HOEHE_1"

then run a new field calculation to return the highest value from the lowest range.

export as new features without the join field and delete identical.

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PhillipKnobloch
New Contributor

Thanks for the Help, 

unfortunately I wasn't able to execute your guidance successfully. A new problem arose with intersecting waterways. The Polygons are cut at waterways which causes lines of different elevation levels to be drawn as a single feature. 

I will revisit again in the future but after having spend a good amount on hours yesterday and today on this I will be giving up for now. 

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