ArcGIS Algorithms

[VasiliosKalogirou]

Is there a way to know what algorithm does ArcGIS use for each operation? For example: which algorithm does ArcGIS use to determine if a point is inside a polygon? Is it the Ray casting algorithm?

[WesMiller]

See if this helps Geometry—Help | ArcGIS for Desktop

[VasiliosKalogirou]

Thank you very much!

There is a lot of helpful stuff in there, but I can not really find what I am looking for. It seems great for using ArcPy though.

[DanPatterson_Retired]

It is very rare that the actual algorithm is published, for example, How Simplify Line works​

They may give references to texts or articles and one can infer, rightly or wrongly.  In the end it doesn't matter, unless it is wrong.  If you do a search on the history of Ray Casting you will find it is only one of many and maybe not the best for all circumstances.  If you have a particular condition you need met, then you can roll out your favourite solution and simply use ArcPy geometry objects themselves and/or convert them to Numpy arrays or generic numeric objects.

[VasiliosKalogirou]

Thank you very much, all these are correct!

The link you mentioned about the line simplification is exactly what I am looking for. Indeed, it seems that only a few of the actual algorithms are published; I cannot understand why as it would be very helpful for the users.

[ChrisSmith7]

If you would really like to know what's going on under the hood of your GIS application, you might want to check-out QGIS. Since it's open-source, you can check the code for yourself:

Welcome to the QGIS project!

Here's the github:

qgis/QGIS · GitHub 

As an example, here's the QgsGeometryAnalyzer class with notes on algorithms:

QGIS/qgsgeometryanalyzer.sip at 91e1554611fe179c802e2355371ae0aa9adbc80c · qgis/QGIS · GitHub

You can also download plug-ins and view their source as well, e.g.:

QGIS Python Plugins Repository

attilaancsin/PolygonSimplifier · GitHub 

[VasiliosKalogirou]

Thanks a lot Chris.

I use both QGIS and ArcGIS and your answer is very helpful on what i am trying to do.

Specifically for the line simplification, you posted the example of QgsGeometryAnalyzer, but the plugin I need to install regarding this particular operation should be the "SimpliPy" one, right?

[DanEvans]

Whitebox is another open source GIS program, which has the quite nice feature that you can view the source code for all of the tools simply by clicking a button in the GUI - no need to worry about checking code out of github and having a suitable IDE etc.