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Ellipses: geodatabase feature class to shapefile

Jeroenvangestel

Hi all,

I work with ArcMap 10 desktop, basic.

I need to convert a polygon feature class from an esri file geodatabase into an esri shapefile. The feature class contains ellipses!
So when converted into a shapefile these ellipses transform into squares, diamonds or stripes.

Is there a solution to this problem?

Greetings and thanks in advance for any comments on this topic!

Jeroen

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Jeroenvangestel

Hi Hardolph,

Thanks again for Your advise.

I've solved the problem by switching projections. The original projection was RD_new, (EPSG) 28992 Amersfoort. I've switched it to GCS_WGS_1984 and exported the data to shapefile and switched the projection again.

In WGS the conversion from ellipse feature to shapefile wasn't a problem any more. The ellipse was converted to a polygon with more than enough vertices.

Greetings,

Jeroen

HardolphWasteneys

Jeroen,

I'm using Win 7 64 bit with 9.3. Generalize will work on multiple selected features. Try an offset of 0.001 for your case; it is scale dependent.
There may be some limit to the number of vertices governed by your AdvancedArcMapSettings file, but it does work. Just work up from there on the offset or down on the number of selected ellipses if it bonks.

Hardolph

Jeroenvangestel

Hardolph, Marco,

Thanks for the input. Unfortunately the densify tool isn't available in the basic or arcview license.

I've gone over the generalize tool-option again and it seems I've been a bit too fast with my conclusion... With a maximum allowable offset of 0,1 I got a pentagram instead of a triangle.

However, this only happens with one ellipse. I have lots of ellipses that need to be converted in one feature dataset. When converting multiple ellipses at once this won't do.

My PC has a windows 7 configuration. I also tried it on a XP configuratio, but with the same results. Maybe I can find a 9.3 version to try next.

So far thanks for Your input!

Jeroen

HardolphWasteneys

Jeroen, Marco,

Densify is an Arc 10 function and that should work if you're there. In 9.3 some combination of SMOOTH and GENERALIZE will accomplish what you need to convert a parametric curve into a series of vertices.
Generalize should work for circles and ellipses, which as parametric curves are defined by only a few vertices and some code. To get the density of points that is suitable for your purpose, start with a low number like 1 or 0.1 and work up, or undo the edit and try a lower number.

What I meant about empty geometry refers to the scaling or coordinate system you are in and therefore what offset value you use with generalize. If too big a number it interprets the feature as empty.

Seems a bit odd that this is happening to your ellipses anyway since exporting a circle or ellipse in Arc9.3 automatically triggers conversion to a series of vertices that approximate the true curve. There is no direct ellipse feature drawing in 9.3 only graphic so I converted a graphic ellipse to a gdb feature which retained the parametric curve definition, then exported to shp.

Since gdb parametric-feature to vertice-defined shp conversion works without intervention in 9.3; I'd suspect you have a problem in 10 with your installation, perhaps as a result of some Windows update, which has been a suspected plague with some gdb functions for me recently.

Some added thoughts: sounds like you are exporting or copy-pasting into an existing SHP. Try instead exporting the layer to a new shapefile i.e. right click on the layer in the TOC and export data if that is how it looks in 10. There may also be a new setting in 10s version of AdvancedArcMapSettings that is too big that defines the number of vertices on export.

Hardolph

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MarcoBoeringa

Hi Hardolph,

When generalizing the ellipses I just get triangles, no matter what maximum allowable offset is given. Is that what You meant by playing with the parameters?

Hi Jeroen,

Although Hardolph points in the right direction regarding his remarks about how the geodatabase stores true ellipses (mathematically instead of a dense line of vertices), I think you will need to use the Densify tool instead of the Generalize tool. Generalize removes access vertices based on tolerances, Densify adds them, and this last thing is what you want when converting to a Shapefile. See the Help topic:

Densify (Editing)

Jeroenvangestel

Jeroen,

you may need to significantly increase the number of vertices by using the generalize tool in advanced editing. Essentially, in the geodatabase your polygon edge is being defined as a mathematical shape or curve rather than a close spaced series of vertices. As loing as the generalize tool doesn't interpret empty geometry it should work.

Try playing with the parameters of the Generalize tool until you get something smooth enough before exporting to shapefile.

Hardolph

Hi Hardolph,

When generalizing the ellipses I just get triangles, no matter what maximum allowable offset is given. Is that what You meant by playing with the parameters?

I'm not sure what You meant by "...as the genralize tool doesn't interpret empty geometry..." What would happen if this occurs?

Thanks,

Jeroen

Jeroenvangestel

Jeroen,

Does your shapefile have the same coordinate system as your feature class? What are your steps you are taking to convert?

Matt P.

Hi Matt,

Yes, it has the same coordinate system.
I've tried to copy-paste the features into the shapefile and tried to export the features to a shapefile:

First I select all features and copy-paste them by a right mouse click into a shapefile.

In an editing session when copying and pasting, the copied feature in the shapefile seems to be an ellipse. When stopped editing the ellipse becomes a square.

Also I tried exporting the data via right mouse click, export data...

Thanks,

Jeroen

HardolphWasteneys

Hi all,

I work with ArcMap 10 desktop, basic.

I need to convert a polygon feature class from an esri file geodatabase into an esri shapefile. The feature class contains ellipses!
So when converted into a shapefile these ellipses transform into squares, diamonds or stripes.

Is there a solution to this problem?

Greetings and thanks in advance for any comments on this topic!

Jeroen

Jeroen,

you may need to significantly increase the number of vertices by using the generalize tool in advanced editing. Essentially, in the geodatabase your polygon edge is being defined as a mathematical shape or curve rather than a close spaced series of vertices. As loing as the generalize tool doesn't interpret empty geometry it should work.

Try playing with the parameters of the Generalize tool until you get something smooth enough before exporting to shapefile.

Hardolph

Matt_Payne

Jeroen,

Does your shapefile have the same coordinate system as your feature class? What are your steps you are taking to convert?

Matt P.

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