Identifying true curves/arcs in ArcMap?

Question

The only good way of creating circles in ArcMap is using true arc, (compound curves) but I need to convert those to vertex (densifying) because of a compatibility problem. I need info for geodatabase and SDO_geometry (arcsde)

and yes there is a way. I use:

UPDATE layer1 a SET arctype = 'compound' WHERE has_compound_curves(a.shape) <> 0;

and then using ET Geotools to densify layer by layer.

But there should be easier way of doing this straightforward in Oracle or ArcMap, and I just want to densify the features that have true arc. I don't want any unnecessary vertices on straight lines and so on.

How can I identify true arcs in ArcMap, and how can I densify them as fast and easy as possible?

Same for Oracle SQL.

Answer 1

I was asked this question today ("How do I identify if a featureclass has curves) and was given some arcpy code suggestions. Modify the following code as you see fit (a flag variable instead of a message for example)

geometries = arcpy.CopyFeatures_management("inputFeatures", arcpy.Geometry())
import json
for g in geometries:
    j = json.loads(g.JSON)
    if 'curve' in j: print "You have true curves!"
    else: print "No curves here"

No curves here
No curves here
You have true curves!
You have true curves!
No curves here
You have true curves!
No curves here
No curves here
You have true curves!
You have true curves!
You have true curves!
You have true curves!
You have true curves!

Answer 2

By using Densify ,Curve segments are simplified through densification by either the Maximum Deflection Angle, or Maximum Offset Deviation parameter.

So Straight line segments will be kept intact.

Answer 3

Building on @KHibma's answer, the data access cursor has the token SHAPE@JSON which can be used to check for curves without importing the json module.

with arcpy.da.SearchCursor ("InputFeatures", ["OID@", "SHAPE@JSON"]) as curs:
    for oid, json in curs:
        if "curve" in json:
            print "{} is curved".format (oid)

Answer 4

I think once you've selected them, you can densify them. The (untested) code below could be adapted to do this. (Assumes Bezier curves qualify as arcs).

public void SelectTrueArcFeatures()
{
    var editor = ArcMap.Application.FindExtensionByName("ESRI Object Editor") as IEditor;
    if (editor.EditState != esriEditState.esriStateEditing)
        throw new Exception("start editing first");
    var fLayer = ((IEditLayers)editor).CurrentLayer;
    if (fLayer.FeatureClass.ShapeType == esriGeometryType.esriGeometryPoint)
        throw new Exception("current edit layer must have polylines or polygons");

    var fSel = fLayer as IFeatureSelection;
    fSel.Clear();
    var fCur = fLayer.FeatureClass.Search(null,false);
    IFeature feat;
    while ((feat = fCur.NextFeature()) != null)
    {
        if(HasAnArc(feat.Shape))    
            fSel.SelectionSet.Add(feat.OID);
    }
    fSel.SelectionChanged();
    System.Runtime.InteropServices.Marshal.FinalReleaseComObject(fCur);
    ArcMap.Document.ActiveView.Refresh();
}

private bool HasAnArc(IGeometry geom)
{
    var segcoll = geom as ISegmentCollection;
    if (segcoll == null)
        return false;
    for (int i = 0; i < segcoll.SegmentCount; i++)
    {
        if (segcoll.get_Segment(i) is ICircularArc 
          || segcoll.get_Segment(i) is IBezierCurve)
          return true;
    }
    return false;
}

Answer 5

this Curves And Lines addin lets you select shapes which have curves in them: http://www.arcgis.com/home/item.html?id=b59665cb906a435da3f8c45332d7cfdf

Answer 6

I created my own solution for this as well, based upon the suggestion by @geogeek. I created a model that compares the source layers vertexes with a vertexes from a densified (using the ANGLE option) copy of the source layer. The output is a layer of vertexes that "don't match" the source. The final step selects all of the source features that intersect the unmatched points, thereby identifying features that contain true curves.

Because this model does not split features at the start and end points of the arc, the entire feature will be exported. Therefore, if you have a single geometry that is connected as "line-curve-line-curve-reversecurve-line", the whole feature will be output, not just the curve portions. Use the points to determine where the actual curve(s) exist.

You can download the model called "Identify True Curves" from the ArcGIS Resource Center "Analysis" gallery.