Calculating shortest route distances when FROM and TO are off road

Question

I have a shapefile of ~10,000 groundwater wells, a shapefile of ~7 points of interest, and a comprehensive road network. I am looking to create a single distance value for each groundwater well that represents the shortest distance route to the nearest point of interest, by road.

My issue (other than being a GIS novice) is that both the groundwater points and the points of interest do not lie directly on the road network. There is a distance from each of these groundwater wells to the nearest road, then that point on the road to the section of road nearest to the point of interest, and then the distance to the point of interest. And I have 10,000 wells to do.

groundwater wells = X

Points of interest = tan O

I was curious how one of you experts might go about this?

Answer 1

There are two ways you can go:

1. Use the standard Closest Facility solver present in Network Analyst (remember that you will need both a valid license for this extension and a built network dataset).

In this case, the groundwater wells points and POIs will be snapped to the nearest road during the solve time. The route will start and end on the roads, which means that the plain distance between the groundwater wells and roads will not be taken into the total length of a route.

2. Use a custom geoprocessing operation that will create the lines between the groundwater wells and the roads (follow this post or this article) and re-build your network dataset.

In this case, the route will represent probably a more relevant distance value (provided that the plain line created to connect each well to the nearest road is actually straight in reality).

You could also just use the Generate Near Table tool to get the plain distance between every well and road and then add this value to the resultant route that connects every well and POI.