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compare two geometries in same feature class

QuangTruong

Hi, I need to compare two features in the same feature class. I'd like to test to see if they intersect. Specifically, I have a feature set composed of lines, and I'd like to know if any given two are intersecting. What is a quick and easy way to do this?

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bixb0012

From what you describe, why not just use the Intersect—Help | ArcGIS Desktop tool? A feature class can be intersected with itself (just put a single feature class in list of inputs).

DanPatterson_Retired

Take a polygon/polyline with 5 points, the first and last are repeated, since it is a closed loop, if the points are sequential and not made up of individual segments. You can't tell this by visual inspection.

Four points, made into 4 segments, hence duplication in points.

Arrange the points as either 4 sequential numbers or pairs of two numbers.

As the question?

Which segments does a particular point (eg (1.5, 1.5) in the lower left) belong to? A little query magic (details depend on how you want to implement this) and it is visually obvious and the query supports that the point belongs to the first and last segment.

Now... There is no `tool` that does this, but you can get at the numbers if you can dissociate the lines to segments if they already aren't segments.... then get the points of the segments. From there it is a `query`.

I did all of this in python and numpy, but it can be done with featureclasses and tables and arcpy if needed.

Original points : clockwise from lower-left
In <SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">:</SPAN> s00 Out<SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">:</SPAN> array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>
From-to points for the 4 segments
In <SPAN class="punctuation token">[</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">:</SPAN> fr_to Out<SPAN class="punctuation token">[</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">:</SPAN> array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>
In <SPAN class="punctuation token">[</SPAN><SPAN class="number token">3</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">:</SPAN> fr_to<SPAN class="punctuation token">.</SPAN>reshape<SPAN class="punctuation token">(</SPAN><SPAN class="operator token">-</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">)</SPAN> Out<SPAN class="punctuation token">[</SPAN><SPAN class="number token">3</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">:</SPAN> array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN> <SPAN class="number token">10.00</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0.00</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1.50</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>
<SPAN class="comment token"># ---- case 1...</SPAN> <SPAN class="comment token"># Is the first point (s00[0] = [1.5, 1.5]) in the fr_to list???</SPAN> <SPAN class="comment token"># This is a `boolean` question, so 1 indicates True and 0, False</SPAN> array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> yes<SPAN class="punctuation token">,</SPAN> it <SPAN class="keyword token">is</SPAN> the first point of the first segment <SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">and</SPAN> the last point of the last segment <SPAN class="comment token"># ---- case 2</SPAN> <SPAN class="comment token"># Same question but shown as a structure that organizes by point pairs </SPAN> array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> first point first segment <SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN> last point last segment‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

DanPatterson_Retired

If you convert the polylines to segments

Split Line At Vertices—Data Management toolbox | ArcGIS Desktop

and segment vertices to points

Feature Vertices To Points—Data Management toolbox | ArcGIS Desktop

Advanced license required.

Once you have your points and segments, you can derive the point coordinates and determine which are shared and what shares them.

This can of course be done within the arcpy PointGeometry, Polyline, and Array classes

Geometry—ArcPy classes | ArcGIS Desktop

Array—ArcPy classes | ArcGIS Desktop

So in your simple example above, you can identify the top-most point, It will belong to 2 and only 2 segments

Alternately, you can use the intersect method of the polyline class and perform and intersection to see if it returns an intersection on the segment.

I will work up an alternate example if you want to work with python

QuangTruong

For instance, I am trying to test whether any two of the four lines in one feature class intersect at a point. In the image below, A & B do meet at a point, whereas A & C do not, and I would like to figure out how to test that relationship and determine the point, if possible.

QuangTruong

Right, I knew my original question was vague.

Basically, what I am trying to do is determine whether or not two lines in any given polyline are touching/meeting at the ends: for instance, in a four-sided rectangle (say a tax lot in a cadastral map), if the lines meet at a point or if they do not (such as if they were on opposite sides of the rectangle).

I'm not sure if intersect is the right relationship, or if there is another relationship description that is more appropriate.

Whenever I intersect (arcpy.Intersect_analysis()) the feature class with itself, I always get all of the lines, when what I am looking for is a point output that represents the specific location of the intersection of those two lines, if they do intersect; or nothing, if they do not.

I've had good luck using cursors in place of other geospatial processing functions, and wonder if they would be appropriate here as well, I just don't quite know how to properly declare the objects in advance and then step through the featureclasses with the cursor to test the spatial relationships against the other features in the same class.

Any help or code snippets would be helpful for me to learn, as I am just starting to get a grasp of the different objects/classes and their methods.

DanPatterson_Retired

A picture would help...

Are the shapes 2 point line segments?
multipoint segments?
is there any existing overlap to begin with?
are you referring to lines crossing or lines meeting at ends?
What is the separation between segments?

Intersecting the layer with itself might be a possibility with a lot of caveat's depending on the above.

I have had success with offsetting a copy of a featureclass by a small finite amount, then intersecting that with the original.

The direction and offset is important, if done right, segments that cross/intersect will remain overlapped after the translation, the rest won't intersect.

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