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Trying to understand DJI GO4 (Maps / GPS / Caching)

MAVIC_2_YTS

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Good morning forum,

I have watched a ton of youtube videos, and read various forum posts from here and other places, yet still, there seems to be allot of confusion (on my part) and contradiction in information provided.

I just purchased a new iPhone 8 Plus to use solely for the drone, it does have a voice / text package on it but no data. What I am trying to understand, is how the maps work. Would I make my current "active" phone a hot spot and tether while I fly? Are the maps able to be downloaded via wifi ahead of time? Or does it just use the GPS in the phone for the maps and I don't have to worry about it?

I know (I believe I know) that the maps are required for Active Track and home position if you move, so what is the best way to achieve that?

Thanks in advance!
 

msinger

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Would I make my current "active" phone a hot spot and tether while I fly?
You can do that if you need the maps and want to download them in real time as you're flying.


Are the maps able to be downloaded via wifi ahead of time?
Yes. You can cache the maps in DJI GO like this:


Or does it just use the GPS in the phone for the maps and I don't have to worry about it?
The drone's internal GPS receiver is used to find its location. That receiver is of course not able to connect to the Internet and download map data. Downloading the map data is a function of DJI GO.
 

MAVIC_2_YTS

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Thanks @msinger it's a shame we can't actually download a region and have it loaded. I understand that use to be achievable when DJI was using "Here" for mapping versus "mapbox".

Another question, is the map actually cached in the DJI app? or is it recalling it from the iPhone cache? this is important because the way iPhone cache's the maps is different versus Android. iPhone stores the cache data to volatile memory which is lost during power off where as Android stores the cache to persistent memory.

If DJI takes the maps from the iPhone volatile cache and stores it in the app, then that would be a non issue.

Thanks.
 

msinger

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Another question, is the map actually cached in the DJI app? or is it recalling it from the iPhone cache?
I'm not sure where the map data is stored on Apple devices. I'm still able to see my cached map data after restarting my iPhone.
 
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MAVIC_2_YTS

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I'm not sure where the map data is stored on Apple devices. I'm still able to see my cached map data after restarting my iPhone.
I think it's one of those things I'll just have to go out and try and see how it works / what works best. Appreciate your insight though!
 

Dave Maine

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Different caches on different devices will have identical map data. The mechanics of how caching is done makes no difference.
 
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MAVIC_2_YTS

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Different caches on different devices will have identical map data. The mechanics of how caching is done makes no difference.
I wouldn't quite agree, Android (historically) cache'd data to non volatile memory. Then, once that cached data was called upon it would move it to volatile (faster) memory during use. If the app, or the device was closed / turned off, it would flush from the volatile memory, but it would remain in non volatile memory to be recalled.

On the other end of the spectrum, IOS devices (historically) used only volatile memory for caching and would not transition that cached data. To take it one step further, IOS proactively monitors the cache and free's up (removes) cached data that has not been used recently to make room for active app's that need to cache (this is where the potential data loss comes into play).

I haven't fully reviewed if this has changed on IOS, but that is how it worked (in the recent past, as for my understanding).
 

apeel

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Drone Valley has an excellent video on Map Caching for both iOS (Apple) and Android devices. In the case of Apple devices, the maps are cached in the non-persistent RAM of the phone itself. Because of this you do have to pay attention to how to create the cache and prevent it from self deleting. It is really well explained in this YouTube video, so I recommend you check it out, whether you are using Apple or Android (I use Apple).

Here is a YouTube Video:

https://youtu.be/CStwnhUdhVU
 
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MAVIC_2_YTS

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Drone Valley has an excellent video on Map Caching for both iOS (Apple) and Android devices. In the case of Apple devices, the maps are cached in the non-persistent RAM of the phone itself. Because of this you do have to pay attention to how to create the cache and prevent it from self deleting. It is really well explained in this YouTube video, so I recommend you check it out, whether you are using Apple or Android (I use Apple).

Here is a link to the YouTube Video:
How To Cache A Map in DJI Go4
Thank you sir! I'll give it a watch tonight, appreciate it!.
 

Meta4

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I think it's one of those things I'll just have to go out and try and see how it works / what works best.
Don't get too worried about maps, they really aren't important.
It's several years since I used them.
Tap the map box and you get the alternative option which is the radar display.
It's much more useful to show where your drone is, which way it is facing and how to bring it home.
 
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Dave Maine

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The mechanics of how the cache behaves are different. The format of the cached map does not. I stand by my original statement.
 
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DanMan32

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It was a while since Rick did that video. DJI may have changed things since then.

The view of the map is cosmetic. Possibly important cosmetic from the pilot's perspective but the lack of having map details will not affect the function of the flight.

Map detail and access to internet has no bearing on Active Track. It may have bearing on waypoint though, but only in the sense of you having a visual reference as you set up the points.
You may be thinking of Follow me mode which originated before DJI came up with the visually based Active Track. Follow Me used the mobile's GPS receiver assuming it has one.

Home point setting mostly only depends on the GPS receiver on the AC. However if you want to reset the home point to your location when the AC is located and flying in another, then you need GPS on your phone/tablet. The iPads with no cell capabilities don't have GPS. Note that doesn't apply to cell capable tablets that simply don't have cell service. The GPS receiver is still there.