If you are including the OLC library in your project directly, you will be 
able to calculate a plus code from the user's device location, and also 
translate any plus code back into latitude/longitude coordinates. All on 
device, without any need for 
connectivity: https://github.com/google/open-location-code/tree/master/java

Calculating the distance could then be performed on the lat/lng coordinates 
using something like the Haversine formula 
(https://en.wikipedia.org/wiki/Haversine_formula) - or, alternatively, 
following something like this wrapper class I created a while ago if very 
rough approximations are good enough for an offline, step-by-step 
navigation: 
https://github.com/bocops/open-geotiling/blob/master/java/org/bocops/opengeotiling/OpenGeoTile.java

In any case, displaying the current and destination plus codes while the 
user approaches might help them find the exact location more easily.

On Tuesday, December 3, 2019 at 6:20:27 AM UTC+1, Abizer Jafferjee wrote:
>
> Actually, connectivity is a big issue because mobile data is still 
> relatively expensive in Tanzania.
>
> Currently the QR code has a deep-link back to the digital address within 
> the app.
>
> One option I thought of was to create a USSD application which can be 
> triggered from the app and would retrieve text directions to the location.
>
> I like your idea about giving some helpful information. How would I 
> calculate the distance between two plus codes? And how would I know the 
> plus code of the location the user is standing at?
>
> Thanks Andres
>
> On Monday, December 2, 2019 at 3:52:54 PM UTC-5, Andreas B wrote:
>>
>> That makes sense, thanks for the explanation. I agree with the conclusion 
>> that plus codes aren't that useful in any scenario where both users are 
>> online, and can just access a database with all the necessary information. 
>> I wonder if it would make sense for your app to use plus codes as a 
>> fallback for scenarios where one or both users sharing an address are 
>> currently *not *online?
>>
>> For example, I assume the QR codes displayed by your app contain an ID 
>> value referencing the address data. If the QR code *also* contained a 
>> plus code directly, that could be used to at least display *something* 
>> even if the user is not currently online.
>>
>> Would a statement like "1.5km to the north-west - more information if 
>> you're back online" be useful, or is connectivity not an issue that needs 
>> to be solved in your app's case?
>>
>

-- 
Public site: http://www.openlocationcode.com/
Github project: https://github.com/google/open-location-code
Demo site: http://plus.codes/
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