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Help with customising maps - Google Maps API, MyMaps etc

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Last Modified: 2019-07-17
I'm posting on behalf of a member organisation with 1,000 members, mainly in the United Kingdom but also internationally. I have exported the home post code of all members to CSV, and used it to create a Google MyMaps map, with a dot for each member's post code. I want to embed this map on our public website, because when people see how many members there are, it might encourage more to join.

However there are privacy concerns, and I have sought advice from ICO (the GDPR regulator in the UK) that it might fall below our members' expectations, because there are some post codes in rural areas where there are only a few houses, therefore this could potentially count as "personally identifiable information".

Therefore I've been looking at various options. First is a heat map, rather than dots. However, from this it will be difficult to say just how many members there are.

Second option is to remove the last two letters of the post code, i.e. "L31 5" rather than "L31 5AA", which would show the dots in a more general position. However since our members tend to be focused in specific regions of the country, this would greatly reduce the number of dots on the map, therefore defeating the object somewhat.

Another option I've heard is limiting the zoom level of the map, to stop being able to see buildings for example. This is the best option I've heard so far, but I'm not sure if it's possible with Google MyMaps. I've seen that this is possible with the Google Maps API, which I've been trying out, but I don't think it's possible to import a CSV into this in the same was as you can with Google MyMaps.

Or is there another option altogether?

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David FavorFractional CTO
Distinguished Expert 2019

Reading through GDPR, guidelines seem to only apply to personal information.

If you represent members with dots by zip/postal code, with no other data (name, street address, etc...) used for your dot, then seems like this passes GDPR requirements.

When in doubt, ask an attorney specializing in GDPR adherence.
meirionwylltSenior Desktop Engineer


Hi David,

I'm researching these solution as a result of concerns raised by ICO, the GDPR regulator for the UK. so I'm satisfied that this needs a solution.
HelpDesk / Programmer
as David Favor mentioned, maybe you can use postal/zip code for markers without any personal information (member name, address, etc.) or you can use only the address

to accomplish, my idea is:
First Option (combine markers into clusters + max zoom):
- cluster the markers on the map, for example using this library:
GitHub: js-marker-clusterer
Clustering Markers- after that, set the max zoom level
maxZoom: zoom
        markerClusterer = new MarkerClusterer(map, markers, {
          maxZoom: zoom,
          gridSize: size,
          styles: styles[style],
          imagePath: '../images/m'

Open in new window

here are some examples :
1. Simple Example
2. Advanced Example (maxzoom)
3. Speed Test
Second Option (heat map + eventually max zoom):
- as you mentioned, generate a heat map from markers, for example using this library:
GitHub Heat Map
Heatmap- optionally set a max zoom

an example from heat map :
HeatMap Example

Hope it helps and I understand correctly your question !
meirionwylltSenior Desktop Engineer


Thanks, I will give this a go