Hello All,
We just release a guide on this in Eos January 2019 newsletter. The 1st paragraph below is for the New Collector (Aurora) on iOS. (For those still using Classic, you can use the Offset menu to collect ortho heights following this older guide How to Configure ArcGIS, Collector for ArcGIS, and Eos Tools Pro for Laser Offset Mapping and Orthom....)
Eos has recently introduced support for Geoid Models (Geoid12B for the US and three Canadian geoid models in the first release). You can record orthometric heights directly in the field in Collector and Survey123 (for iOS and Android only for now). The January 2019 issue of Eos Newsletter explains the workflow on how to add the Z-Value in your map. The article is titled: How to Record Orthometric Heights in Collector v18.1.0 (Aurora) with Your Eos Arrow GNSS Receiver
For Android, still on Collector Classic, there is no Z-value support yet, but you can still record the orthometric height in the ESRI_GNSS_ALTITUDE field. As long as your setup is properly made as per this guide, and Eos Tools Pro elevation is configured for "Orthometric", orthometric heights will be recorded in the above field instead of the Ellipsoidal height.
We will be adding geoid models for other countries in a near future (Australia very soon). If requiring a specific country, please do not hesitate to send your inquiry at info@eos-gnss.com.
Hope this helps !
Jean-Yves