Active View % measurable impressions with Custom Native Ad Formats on mobile

[Antonio C]

Hello, 

I'm trying to register the following metrics in the reporting for our Custom Native Ad Format ads on iOS and Android:

Active View % measurable impressions

Active View % viewable impressions

These metrics are reported correctly for our banner ads, but not for our Custom Native Ad Formats. 

I understand that the GAM SDK handles impression tracking for the banner ads, while for Custom Native Ads, we must implement our own impression tracking. We've done this successfully and impressions are being counted for these ads. However, the Active View metrics remain at 0. 

The only mention of viewability for Custom Native Ad formats I've found in the GAM docs is in the section on Open Measurement: https://developers.google.com/ad-manager/mobile-ads-sdk/ios/custom-native-omid

Is Open Measurement the only way to record Active View metrics, or is there another method? Have others successfully recorded these metrics for their Custom Native Format ads on mobile? If so, how?

Thanks in advance!