09-05-2018 02:02 AM
is it possible to convert a polygon to polyline in the Spatial Modeler?
Maybe with the Functional Attribute?
09-05-2018 10:05 AM
Yes, the basic approach in Generate Functional Attributes would be something along the lines of
However if you have holes in the input polygons you will need to deal with those. And there may be other operations required based on the nature of your specific input data.
09-06-2018 05:57 AM - edited 09-06-2018 08:01 AM
Yes, this is because of the way that some formats store the vertices for a polygon. If the end point isn't the same as the start point (i,e, there';s an assumption that to close the polygon you need to draw from the last point back to the first) then when you convert to POINTS you literally get the stored points. So when you join those dots to form a line there's no indication to draw a segment from the last point to the first.
POINTS is one of the few operations in GeoMedia (and the equivalent Operator) which doesn't make the assumption that you want to "close the gap". You may wish to register an Idea to add that functionality.
One thing you could try in the meantime is to densify the geometries first. That way the gap will at least be smaller.
09-06-2018 06:19 AM
One clarification. I don't *think* this involves the nature of the source data and its format, as all data regardless of source should be presented in Spatial Modeler with closed polygons. I think it's just the fact that the POINTS expression function does not return the endpoint that closes the polygon and matches the startpoint. This is probably just a design mistake, but we've confirmed that it works that way for both GeoMedia and Spatial Modeler expressions. Ian's suggestion of submitting an Idea is a good one as we would have to consider implications of changing that behavior. - Hal
09-06-2018 09:57 AM
Try this instead:
(and thanks to the GeoMedia teams!)
09-06-2018 10:07 AM
Two further observations: