the population assigned to each node in thiessen polygon

Hello Majid,

To calculate the actual population served you would need to multiply the density with the area of the thiessen polygons you generated to apply the loads. If you are familiar with any GIS application (E.g. ArcGIS or QGIS) you could find out the area of each of the thiessen polygons by bringing in the thiessen polygon shapefile in it and querying to calculate the ares of the polygons.

Once this is known you can multiply the density to calculate the population being served at that node.

Hi Yashodhan, Thank you for the reply and the method you provided. I actually thought of this method but the problem is that many areas created by thiessen polygon for the nodes fall inside two different density areas (boundary nodes) and this makes it difficult to easily find the population related to each node. Since the software makes all these calculations, I was wondering if it might be stored somewhere for easy access?

Hi Majid,

SewerCAD only uses the information internally and the visible result is the overall base flow to be applied to a particular pattern and node. 

However, you'll notice that, after the LoadBuilder run completes, it gives you the option of assigning population density types with a pattern. So, if the load for a particular manhole comes from two different population density types that overlapped its respective service area layer (Thiessen polygon), you could assign a pattern with the same name to each one. Then, you would be able to see in the manhole properties (or Sanitary Load Control Center) the overall base flow applied to each pattern (density type). For example if a particular manhole's service area layer overlaps two different density polygons, you'll see two separate load entries for that manhole, with the pattern corresponding with the respective density type.

Since you know the area, population density and load density for each density type, you could back-calculate the population from that, and add them together (for cases where multiple density types are assigned to a given manhole). However, determining the area (that overlaps between the density polygon and the Thiessen polygon) would require GIS tools.

I have added this information to the following article: How do each of the LoadBuilder methods work?

Aside from this, if we were to enhance SewerCAD to be able to display this information automatically, can you help us understand how it would help you, and do you have a suggestion on where and how this population should be displayed? 

Hi Jesse,

Thank you for the thorough answer to my question. you made it clear that I need to make the calculations myself and sewercad does not directly provide the answer. To answer your question, It is the first time I am asked to provide the population assigned to each manhole with other data. I believe it is an easy measure to check if the loads assigned to each manhole is correct without the need to check the calculations. If I were to add this option, I would add it in the last step of the loadbuilder tool where the loads related to manhole is shown. 

Regards,

Majid 

Thanks for the feedback, I have reported it to our development team as feature request # 610598