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Raster to Polygon: Polygons not in proper location (offset)

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a month ago
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NateLemoine
Emerging Contributor

Hello,

I am trying to create a polygon from a .tif raster. When I use the Raster to Polygon tool, the generated polygons are all offset to the north by quite a bit.

Screenshot (2).png

I am aware of all the projections/transformations. I have been through every layer/feature and they are all set to the same projection and coordinate system. When I create the polygons, I make sure to set the output coordinate system to the same as the input raster, I set the extent to the same as the input raster, and I use 'snap to raster' to snap to the input raster. Despite all of that, it still returns polygons that are offset into the wrong position. Can anyone help me out?

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Ed_
by MVP Regular Contributor
MVP Regular Contributor

what happens if you don't do any of this "I make sure to set the output coordinate system to the same as the input raster, I set the extent to the same as the input raster, and I use 'snap to raster' to snap to the input raster. " and just do a basic `Raster to Polygon` conversion?

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Robert_LeClair
Esri Esteemed Contributor

One thing I would try is remove the Snap Raster parameter and run the tool again.  Does the resulting polygon still offset to the north?  Also, is the source raster an integer raster?

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DanPatterson
MVP Esteemed Contributor

Try, a new map, empty, no basemap etc.

Add the raster, and check the coordinate system of the map, (it should be the coordinate system of the first added layer).

When you specify the extent, in the tool's environment properties, you indicate that you use the extent of the input raster to convert... that is perfect  (see the note on "extent" in the tool help  Raster to Polygon (Conversion)—ArcGIS Pro | Documentation

If the offset still occurs in this environment, what is the offset in size? 


... sort of retired...
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NateLemoine
Emerging Contributor

Hi all,

We've gone through all of the steps. We've tried running just the basic conversion, which is similar to the comment of not using Snap to Raster. We've made a new map, imported the raster as the first file, and then tried to convert the polygon with no options, with the coordinates set, and with the coordinates + snap to raster set. We still get the same offset. And as you can see, the offset is pretty large, several kilometers.

Screenshot (12).png

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NateLemoine
Emerging Contributor

Just as an update. The issue is in 'Create Multipart Features'. If I deselect this option, the raster appears right where it is supposed to be. Is this a bug in the software?

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NateLemoine
Emerging Contributor

The only way to create a multiple part feature accurately is to Raster -> Polygon, DO NOT use Create MultiPart Feature, then Dissolve the multiparts on an ID column. Everything is right where it ought to be if it is separated into two steps. So this seems to be a pretty big bug in the software.

DanPatterson
MVP Esteemed Contributor

You should report it.  It may not have been reported before


... sort of retired...
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Robert_LeClair
Esri Esteemed Contributor

I looked at the internals and I do not see an existing BUG report on this workflow.  I'd recommend you contact Esri Support Services to create this bug report with them.  Agree - this is a pretty big bug in the S/W.

NateLemoine
Emerging Contributor

Thanks all. I did send ESRI a message. But at least I know the workaround now.