Location high accuracy mode with wi-fi turned off My understanding: location mode «High Accuracy» is more efficient than «Device only» because it unburdens some of the GPS task by using Wi-Fi networks information.

Consider these settings:


«Scan always available» is set to «off»
«Keep Wi-Fi on durin sleep» is set to «always»


If «location» is enabled in «High Accuracy» mode, but the Wi-Fi is disabled, does this mean that location works as if in «Device Only» mode?

So in order for the «High Accuracy mode» to actually work you have to have either «Scan always available» «on» or the Wi-Fi on. Is that correct?
No, high accuracy mode without WiFi is not the same as device only because 


The mobile network provider location source is also used in high accuracy mode but not device only. 
Assisted GPS may be used to reduce the time to get a location fix when you use a network connection, either WiFi or the mobile data connection. "Download GPS assisted data only over WiFi networks" determines whether the mobile data connection is used for assisted GPS. Information about the GPS satellites expected to be in view is passed over the data connection, and this is much faster than the GPS receiver searching for satellites. 


No, for high accuracy mode "to actually work" does not require WiFi. GPS provides better location accuracy (~5m) than WiFi location (~25m) regardless of whether WiFi is enabled. That is why it is called high accuracy. WiFi location is much faster than GPS, but not as accurate. For many applications, it may be sufficient to know what city you are in but not what street.