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Hello!

Some polygons disappear in the transformer dissolver, it doesn´t matter if I use group by or not.

Coordinaterounder, Densifier, Snapper fix some problem but other polygons disappear instead.

Geometry validator with no result.

Tips or idea?

What exact version of FME?

Can you share the geometry so we can reproduce the error? Just strip the attributes and write to FFS.

You can easily anonymize the features with an offsetter and rotator if needed.


The all point of the Dissolver is to dissolve polygons and therefore make some 'disappear', can you visualize your unexpected results and share it?


Here is a screenshot and input file for this example...

 

small-example3-mergeid.zip

Try to dissolve with group by for the attribute mergeid...


Here is a screenshot and input file for this example...

 

small-example3-mergeid.zip

Try to dissolve with group by for the attribute mergeid...

My guess is that there are inconsistencies between the features, especially mis-alignement of nodes, possibly using a coordinaterounder before the dissolver might help.

 

 


My guess is that there are inconsistencies between the features, especially mis-alignement of nodes, possibly using a coordinaterounder before the dissolver might help.

 

 

It works sometimes with coordinaterounder. But polygons disappear elsewhere. Very frustrating!

 

 


What exact version of FME?

Can you share the geometry so we can reproduce the error? Just strip the attributes and write to FFS.

You can easily anonymize the features with an offsetter and rotator if needed.

FME 2016.1.1 - 64bit

 

FME 2016.1 - 32bitFME 2015.0 - 32bit

 

FME 2015.1.1 - 64bit
It works sometimes with coordinaterounder. But polygons disappear elsewhere. Very frustrating!

 

 

I can imagine....I would suggest contacting support

 

 


Is it possible that some of your polygons contains arcs?

I've seen quite a lot of similar bugs on datasets containing arcs, probably due to floating point precision issues.

Consider pre-processing your data with an ArcStroker and a Snapper (segment snapping) before the Dissolver.


@sjodin

I can advise that we made massive improvements in this area in FME 2017. Please try the original dissolves with FME 2017 beta and let us know at support@safe.com if there are still issues. @david_r - you'll be pleased to know that the improvements also included robustness in arc situations, so there should be no need for stroking and snapping prior to dissolve.


@sjodin

I can advise that we made massive improvements in this area in FME 2017. Please try the original dissolves with FME 2017 beta and let us know at support@safe.com if there are still issues. @david_r - you'll be pleased to know that the improvements also included robustness in arc situations, so there should be no need for stroking and snapping prior to dissolve.

Thanks Dale, that's great news!

 

 


@sjodin

I can advise that we made massive improvements in this area in FME 2017. Please try the original dissolves with FME 2017 beta and let us know at support@safe.com if there are still issues. @david_r - you'll be pleased to know that the improvements also included robustness in arc situations, so there should be no need for stroking and snapping prior to dissolve.

That's great news!

 

We have also experienced quite some issues with polygons disappearing when using the dissolver. Looking forward for FME 2017!!

 


@sjodin

Hi,

Both areas in the sample have huge spikes...

If you use spikeremover at max 1 degree, the output will dissolve correctly.


That's great news!

 

We have also experienced quite some issues with polygons disappearing when using the dissolver. Looking forward for FME 2017!!

 

We are hopeful that most issues will be one with FME 2017, but that said, we have a final step we will introduce in FME 2018 that will end this problem we hope for good. In FME 2017 in some really bad cases you need to do a snapping first, but my understanding is that we know of no cases where a first snapping followed by dissolve has issues in FME 2017

 

 


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