This read-only value, in meters, reports a GPS uncertainty parameter associated with the vertical component of the device's last location fix, as returned by the GPS receiver. An admin uses this to gauge how much to trust the altitude reading (c3gLbsHeight) reported for the same fix, since vertical GPS measurements are typically less precise than horizontal ones. For example, if this uncertainty value is large, the admin should treat the reported height as only a rough estimate rather than a precise elevation figure.