Why is US Census data showing "households" over water?

[StephScavelli]

I put together a map of New York showing the type of fuel used to heat a household. See here:

When I zoomed in on New  York City and Staten Island, I noticed all these "households" over water. See here:

The data I used is from the American Community Survey 2021 5-year data set.

I sourced my data from this link:
TIGER/Line with Selected Demographic and Economic Data (census.gov.)

Why are data points, which are supposed to represent households, being placed over water?

[DanPatterson]

The coordinate system for the data are in

GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6
378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.0174532925199432

What is your basemap?  

I would use a basemap from that source or something (not in Web Mercator) that you can control any projection issues between the basemap and the data.

[StephScavelli]

I think you're right to start looking at the coordinate system for the first point to troubleshoot. I am using ArcGIS Pro and selected a basemap from their default collection. 

[Eugene_Adkins]

I’m not familiar with the waterways of New York so the answer could be @DanPatterson‘s … or the answer could be houseboats 😂

[StephScavelli]

When in doubt, the simplest answer is the correct one - boat houses it is!

Jokes aside, I hope I can figure this out because the map looks very unprofessional with hundreds of data points situated over water. 

[JoshuaBixby]

Census data is commonly summarized by area, where are the points coming from?  If I download the ACS_2021_5YR_COUSUB_36_NEW_YORK geodatabase it doesn't have any points in it.

[StephScavelli]

Hi @JoshuaBixby  Right, the shapefile in the geodatabase doesn't have points. The data set comes with standalone tables that then can be joined to the shapefile. The symbology of the shapefile is then changed to Dot Density and I select which data to display. 

[JoshuaBixby]

The answer lies in the fact that you are relying on dot density symbology for some polygons that have perimeters that span water and land.  If you want to ensure all the dots are in land, you will have to intersect the census layer with some kind of water/land layer to get census area definitions that only include land.