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Caching maps for off-line use

larryc43230

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About three weeks ago, I purchased my first drone, a Mavic Air. I tried using my Samsung Galaxy S8 phone with the remote control, but I soon realized that these no-longer-young eyes need a larger screen. I purchased a Samsung Galaxy Tab S2 tablet, 8" display, WiFi only, dedicated for use only with the drone's remote control. I use DJI GO 4 as my flying app, and would rather stick with that app at least until I gain more experience with operating a drone.

This combination works well, but so far I've used it only near my home, inside the "WiFi bubble" around my home. I'll soon want to fly the drone somewhere that has scenery that's a lot more interesting to see than my yard.

After reading some forum posts here, I've become concerned about maps, the ones displayed in the DJI GO 4 app when I fly the drone. What happens when I leave my home area and the tablet isn't connected to a WiFi network? Will I still be able to see a map representation of where I'm flying and if so, how? I really don't want to have to tether my cell phone to the tablet and/or remote (to use the cellular network to get maps); the stuff I already do with my cell phone drains the phone's battery quickly enough the way it is now.

I've read about downloading maps to make them available for off-line use, when I'm in some remote area. Can anyone point me to a step-by-step guide for downloading and storing maps that the app can use?

Thanks for any and all suggestions!

Larry
 

Dronason

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Plenty on youtube, by example:



In general, you have to plan your flight and pre-download maps for the area of the flight when you have internet connection.
Alternative is to use your phone as a wifi access point the day of flight so its internet access is shared (tethering). Then the map will be displayed and you can disable tethering on your phone, map will stay for the time of flight.
 

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Are the maps REALLY that useful anyway?
I use the radar view 99% of the time as i find it far more useful to see where i am in relation to the drop to keep the RC pointed along with where the drone is looking relative to me. That actual exact geographical location under the mavic doesnt matter to me.
 

Dronason

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Are the maps REALLY that useful anyway?
I use the radar view 99% of the time as i find it far more useful to see where i am in relation to the drop to keep the RC pointed along with where the drone is looking relative to me. That actual exact geographical location under the mavic doesnt matter to me.
It depend on the distance and over what you fly. It is by example easier to check on the map if you are flying over some roads so you don't fly on top of it but just cross them shortly when needed. Same with village or houses. That's situations dependent. For my use of a drone, it is very important.
 

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I just flick the camera down to check things like that. Then again i rarely go more than 600m away as well.
 

larryc43230

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Thanks for the tips, everyone. I've learned how to download maps using the DJI GO 4 app, and I just downloaded all the maps I'm likely to need for the time being. Since the drone can fly just fine with or without maps, and I know how to download maps before traveling to a new area, I'm a happy camper.

Thanks again!

Larry
 

Prismatic

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Thanks for the tips, everyone. I've learned how to download maps using the DJI GO 4 app, and I just downloaded all the maps I'm likely to need for the time being. Since the drone can fly just fine with or without maps, and I know how to download maps before traveling to a new area, I'm a happy camper.
Only one location will be cached, so if you downloaded multiple locations, you're about to be less happy.

Where I fly most, in the Great American Outback (CO/UT/AZ), cellular service is extremely spotty, tiny pools of connectivity in a vast unconnected landscape. Having the satellite view of my flight-zone would be so useful.

But map caching, at present, is practically useless to me. :mad: I should be able to cache multiple locations, and DJI Go4 should call up the appropriate cached data based on the current GPS coordinates. Give me that feature and I'll be a very happy camper!
 

conchman

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Only one location will be cached, so if you downloaded multiple locations, you're about to be less happy.

Where I fly most, in the Great American Outback (CO/UT/AZ), cellular service is extremely spotty, tiny pools of connectivity in a vast unconnected landscape. Having the satellite view of my flight-zone would be so useful.

But map caching, at present, is practically useless to me. :mad: I should be able to cache multiple locations, and DJI Go4 should call up the appropriate cached data based on the current GPS coordinates. Give me that feature and I'll be a very happy camper!
It allows me to download about 7 off-line maps, why do you say it only allows one map? Is "caching" maps the same as "off-line" maps? Does anybody use google maps as their 'map' for DJI Go 4 and does it automatically use the right 'off-line' map in this scenario? I watched the youtube tutorial how to load google maps into Go4 but I couldn't get it to work.
 

larryc43230

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It allows me to download about 7 off-line maps, why do you say it only allows one map? Is "caching" maps the same as "off-line" maps?
Yes, I'm confused about this, too (I'm the one who started this thread). I probably shouldn't have used the word "cache" in the post, since that might be causing the confusion.

After reading some responses, I launched the DJI GO 4 app on my Android tablet, then from the "hamburger" in the upper-right corner selected "Offline Map", then followed the prompts and downloaded eight different map segments for future use. These maps range from my home territory in Central Ohio (I used that as a test) to several areas in northern Virginia, where I'll be spending several days this fall. Sitting at my desk here in Columbus, I can view all eight of these maps, and I presume the app will be able to use them anywhere I go, on or off the grid. And as far as I can tell, I can add as many map segments as I like, limited only by storage space on the tablet (the maps are apparently stored on the tablet, since I can view them in the app with the remote control and drone off at the moment).

Prismatic, can you describe to us how you're caching a map segment? You don't seem to be using the app's Offline Maps feature.

Larry
 

conchman

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Yes, I'm confused about this, too (I'm the one who started this thread). I probably shouldn't have used the word "cache" in the post, since that might be causing the confusion.

After reading some responses, I launched the DJI GO 4 app on my Android tablet, then from the "hamburger" in the upper-right corner selected "Offline Map", then followed the prompts and downloaded eight different map segments for future use. These maps range from my home territory in Central Ohio (I used that as a test) to several areas in northern Virginia, where I'll be spending several days this fall. Sitting at my desk here in Columbus, I can view all eight of these maps, and I presume the app will be able to use them anywhere I go, on or off the grid. And as far as I can tell, I can add as many map segments as I like, limited only by storage space on the tablet (the maps are apparently stored on the tablet, since I can view them in the app with the remote control and drone off at the moment).

Prismatic, can you describe to us how you're caching a map segment? You don't seem to be using the app's Offline Maps feature.

Larry
It actually only allows me to download 7 or 8 (not near my phone right now) off-line maps, it tells me to delete one before I can download more. Not sure why this setting is like this, since the map is only like 80mb and I have dozens of GB's of space on my phone. I am sort of new but I fly off-line a lot, and I could really use some help with off-line maps as sometimes they dont work for me (this may have been due to DJI changing the map provider a few months ago).
 

Prismatic

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Yes, I'm confused about this, too (I'm the one who started this thread). I probably shouldn't have used the word "cache" in the post, since that might be causing the confusion.

After reading some responses, I launched the DJI GO 4 app on my Android tablet, then from the "hamburger" in the upper-right corner selected "Offline Map", then followed the prompts and downloaded eight different map segments for future use. These maps range from my home territory in Central Ohio (I used that as a test) to several areas in northern Virginia, where I'll be spending several days this fall. Sitting at my desk here in Columbus, I can view all eight of these maps, and I presume the app will be able to use them anywhere I go, on or off the grid. And as far as I can tell, I can add as many map segments as I like, limited only by storage space on the tablet (the maps are apparently stored on the tablet, since I can view them in the app with the remote control and drone off at the moment).

Prismatic, can you describe to us how you're caching a map segment? You don't seem to be using the app's Offline Maps feature.

Larry
I'm using an iPad Mini 4, and there is no "Offline Map" choice from the 'hamburger' menu. If that feature is present on Android, I may need to dump the iPad in favor of an Android tablet!

Do the Android off-line maps in DJI Go4 include the satellite imagery? If so, I am definitely dumping the iPad in favor of an Android tablet!
 
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larryc43230

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It actually only allows me to download 7 or 8 (not near my phone right now) off-line maps, it tells me to delete one before I can download more. Not sure why this setting is like this, since the map is only like 80mb and I have dozens of GB's of space on my phone. I am sort of new but I fly off-line a lot, and I could really use some help with off-line maps as sometimes they dont work for me (this may have been due to DJI changing the map provider a few months ago).
As a test, I just tried downloading a 9th map segment. The app started downloading data, but when it got to 39% it stopped and displayed "You must delete some offline region and resume download", followed by a cryptic button that simply said "Yes" underneath.

Because the app started to download data and then stopped at 39%, it would seem the limit is somehow memory- or storage-space limited rather than limited to a fixed number of maps. If this is memory-limited, it could also mean that the app might allow more or fewer map segments depending on how much total information is included with the map segments you download. It would be nice if there were documentation on this.

Larry
 

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I'm using an iPad Mini 4, and there is no "Offline Map" choice from the 'hamburger' menu. If that feature is present on Android, I may need to dump the iPad in favor of an Android tablet!

Do the Android off-line maps in DJI Go4 include the satellite imagery? If so, I am definitely dumping the iPad in favor of an Android tablet!
No its not satellite or hybrid, just road I believe. I have had mixed results with off-line maps, but as I said in another post, it may have been due the one update where off line maps were not available while they were switching map providers a few months ago. I will be flying off-line while in Europe over the next few weeks, I will tell you how it goes.
 
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larryc43230

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I've been able to download several offline maps (see my previous post), but I still don't seem to be able to use them reliably.

Earlier today, I took the drone to a location (a local park) that sits near the middle of one of the map segments I had downloaded. There was no WiFi available at that location. I fired up the remote controller, the drone, and the DJI GO 4 app and launched the drone. The drone had a solid GPS signal, with at least 12 satellites, at all times. The app displayed the usual view from the drone's camera, with nothing but a black box in the lower-right corner. The black box displayed the word "MapBox" in its lower-right corner, but was otherwise just black. I maximized the black box in the corner with a finger press, but all I saw was a screen-filling black box with the word "MapBox" in the corner. The camera view was now in the lower-right corner, as expected. Just for fun, I switched from Standard view to Hybrid view to Satellite view to see what would happen; nothing changed, just a big black emptiness staring at me.

I'm 100% certain that one of my offline maps includes the area I was in, in fact, the park is near the center of that map segment.

Why didn't the offline map display when I tried to view it in the field, away from WiFi? Is there some other setting I've missed that I need to change? Is there something else I need to do (like somehow select one specific map from the list) to make this work?

Any suggestions would be most appreciated.

Larry

P.S. After I got back home, I tried a different test: I simply turned off WiFi access on the tablet (a Samsung Galaxy Tab S2 with no cellular). When I took the drone outside and fired everything up, I WAS able to see the offline map for my home location. (I had also downloaded that map segment.) Why am I able to see the offline map for my home location but not another offline map for just a few miles away?
 
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Prismatic

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I feel your pain. At times, the map (and satellite!) caching has worked seamlessly for me. It’s beautiful: far from cell service, not to mention WiFi, I fly with a detailed satellite imagery that provides vital in-flight position knowledge.

Then I want to fly down into a tight canyon, and ... NOOooo! The map view is empty! Why?!? I cached this place!

Please. All I want is a reliable, semitransparent way to cache detailed location data—most critically, satellite imagery—from an online source, and have that data available offline, seamlessly displayed in the interface at flight time.

Ideally, I should be able to cache as many locations as I wish, without software limitations or data expiration. And also, of course, be able to easily delete cached data that’s no longer needed.
 

larryc43230

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I'm not sure what went wrong with my previous attempt to use offline maps, but today's attempt was much more successful.

While at home and logged into my home WiFi network, I deleted all the offline maps I'd previously downloaded. My thinking was that perhaps one or more of those maps had somehow been corrupted or incompletely downloaded. All the maps looked OK when viewed in the DJI GO 4 app, but they could still have somehow been corrupt. I had also reached some space limit when I downloaded maps the first time: When I tried to download an additional map, I got an error message telling me I would have to delete an existing map segment to free up space. This time, I downloaded only two map segments, one for the area near my home and the other centered on the area I had chosen for my next test flight.

I drove to an area several miles from home (Hoover Reservoir in Westerville, Ohio). I was far away from any WiFi source. I flew the drone for almost an hour, and this time the offline map I had downloaded displayed as advertised throughout all the flights. It was a real pleasure to see the map display, and I felt a whole lot safer venturing farther out with the drone.

Conclusions: Either the maps I had previously downloaded had somehow been corrupt and wouldn't display, or my downloading so many map segments that I bumped up against some upper limit caused the app to hiccup and not display any maps.

Larry
 

LeafPeeper

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I'm struggling with this mess too. Download the map segment while at home, go to the site with no wifi/cell, nothing but a black box for a map. I had previously been able to get it to work by ensuring I turned off wifi/cell before running Go and trying to fly, but doesn't seem to help now. Anybody else know of any tricks to get this to work reliably?

LP
 

larryc43230

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The solution(s) I found might or might not help you, but it couldn't hurt to try these two approaches:
  • If you've maxed out the map storage and seen an error message that says you have to delete an existing map segment to free up space, delete a couple of the maps you've downloaded. I'm convinced the app gets flaky when the space reserved for map storage is maxed out (or nearly maxed out).
  • Delete and re-download the map that wouldn't display, then try again. You might have somehow wound up with corrupted data that won't display.
Larry
 

LeafPeeper

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Thanks Larry. Unfortunately I've tried both of those things and I still have the same issue. I even deleted all my downloaded maps and just downloaded my map for home. If I turn off wifi/cell and start from scratch, I either get a black box, or I get a simple map with no Mavic arrow. This is really a PITA. I want to fly in several locations without cell service.

Thanks,
LP
 
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