Here are some ways to use GIS tools to display overlapping polygons to help planning departments understand 911 and 5G resourcing needs?We have two products that represent the a couple of approaches we've used to show data in our mapping systems. The first approach is figuring out how to display Public Safety Answering Point (PSAP) polygons with overlapping Authorities Having Jurisdiction (AHJ) polygons. PSAPs are the service areas for the US 911 system. Whoever calls 911 in the US is sent to a PSAP answering center and provided 911 services from there. AHJ polygons show the service areas for separate police, fire and ambulance services. Not every PSAP has separate AHJ areas. The PSAP data is contiguous and covers all of the US but some PSAPs have separate AHJ boundaries for responding Police, Fire and Ambulance service areas. Here's an example of PSAP boundaries in the New York area the boundaries are yellow):
Then we "stacked" the AHJ polygon layers on top of the PSAP polygons. We used a separate data layer for police, fire and ambulance service areas. Here are the fire service polygons in red on top of the PSAP polygons:
So now the analysts can see where there is AHJ police coverage and if the polygon boundaries properly overlap with the PSAP polygons. Then we added Police boundaries in blue:
Finally we put the ambulance or EMS (Emergency Management Services) on top of the other polygons:
We've also made the polygon boundary lines thicker so that they're easier to see on the imagery. This seemed like an intuitive way to display the polygons but if you're zoom level is high enough you won't see different polygons. You also can't see what polygons are underneath the layers that display on top of the PSAP polygons. The only way to really be sure what AHJ polygons are covering an area is to do an info query into the map and see how many different polygons are found.
The second approach we used was for broadband wireless data coverage polygons. For any given location in the US there can be over 30 separate broadband wireless coverage polygons. Since there are so many it didn't make sense to have a fill that might slow down display. The polygons don't completely cover the US so it might make sense to have a very light fill. Here is what that the polygons look like with green borders:
Many users of this data will want to view the data in this manner for a visual check of what the polygons look like. Other users will want to know about the emergency response area they are interested in. The conversion of analog 911 systems to digital systems requires State and city GIS planning and those users will need to view PSAP and AHJ polygons. Or city planners will need to view broadband service exists for buildings or homes so that they know where to permit broadband antenna licenses first.
What are some other ways to show this type of data? Are there use cases similar between telecommunications and other industries where the same approach will work well?
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Lamont Norman
Product Manager GeoEnrichment & Telco
Pitney Bowes
Boulder, Colorado
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