spurious horizontal contour lines depending on number of contour levels

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
python
Domain
data-visualization

Research direction

Start by reproducing the reported map with different numbers of contour levels and plot domains, using the two linked example images as visual references. Trace the contour-rendering entry point responsible for producing the horizontal lines; done means the spurious lines no longer appear while valid contours remain.

Written by the indexing model from the issue text.

Description

I'm seeing an issue where spurious horizontal contour lines appear on my map depending on the number of contour levels I choose. I can also make the horizontal lines go away by 'zooming out' or broadening my plot domain.

Here's an example that has more contour levels and shows the problem (note the two horizontal lines, one near middle of plot, one near bottom):
more_contours

And here's an example that has less contour levels and the problem goes away:
less_contous

Dominant language
Python
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