OD-Cost Matrix - Origins can not be reached

[ulhmu]

Hello community,

I just started with ArcGIS and am currently working on a project, where I create OD-Cost Matrices to later use them in another program.

The idea was, that I created centroids based on a grid, that serve as the Origins for the Cost-Matrix. As destinations I have locations of potential facilities.

I chose 23km as a distance restriction within the destinations should be reached. Now I have the problem, that not all origins are reached from the facilities that should be in the 23km radius. This can be seen in the image, where I highlighted the lines leaving from one facility to all the origins in its reach.

The highlighted polygon is created with the Service Area function, leaving from this facility, which shows, that there are more origins in the 23km radius, that should be reachable.

Does anyone know, why the lines don't reach all centroids in the 23km radius from the Service Area polygon? Is there maybe another solver for the cost matrix that would cause this?

[MelindaMorang]

Are those grid lines the streets (edges) in your network?  If so, then it's likely that some of the points are being snapped to the street locations outside the 23km cutoff distance.  You an see where the selected streets extend beyond the edge of the service area.

When you do a network analysis, the input points must be "located" on the network, meaning the closest non-restricted location on the network is found, and that location is used as the start and end point for the analysis.  Since it looks like your evenly spaced input points are much denser than the grid network, a lot of them will be snapped a fairly large distance to the closest location on the grid.  The snapping distance is not counted as part of the 23km cutoff.  Here is some documentation about the locating process: https://pro.arcgis.com/en/pro-app/latest/help/analysis/networks/locating-analysis-inputs.htm