Download offline maps

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Download offline maps

Postby heinoomen » 2017-11-17 7:48

Hello
I am trying to download offline satellite imagery for site visit where I know I do not have cell coverage.
However I keep receiving the error message "Download error: The downloaded data is not an image". If i switch on ignore image errors and ignore network errors, the download proceeds but I already have >999 failed images. What is the reason for this?
Regards
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Re: Download offline maps

Postby Zax » 2017-11-17 8:17

heinoomen wrote:Hello
I am trying to download offline satellite imagery for site visit where I know I do not have cell coverage.
However I keep receiving the error message "Download error: The downloaded data is not an image". If i switch on ignore image errors and ignore network errors, the download proceeds but I already have >999 failed images. What is the reason for this?
Regards


The reason is mainly depending on the map source you are downloading images from.
For example,
1) if the map provider only provides map content from zoom levels 0 to 18, then all your requests for lv 19 and lv 20 would be failed.
2) Some map provider, like Google, may only provide lv 18 - 20 high-resolution images for downtown or major region, if you choose a larger region which includes both downtown and countryside, or wild regions, then some of these downloading would be failed. (because the server is lack of those data)
3) Map server's temporary busy traffic may also cause some failure.
4) Some commercial map provider, like Google, may restrict or ban your downloading if you download too much image within a period of time, because these data are commercial, and most of them do not allow public users to download. You can contact their sales team and remove that restriction with some wirtten permission.
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Re: Download offline maps

Postby Uday » 2017-11-17 15:19

heinoomen and Zax,

I am also having same trouble with downloading offline map.
What I tried that select one resolution e.g 17 and it works , however sometimes it shows image error.
We can go to ''Options" at bottom and scroll option "Ignore Image Errors" and "Ignore Network Errors" it continues download with many failed images.

But if we choose only single resolution e.g 15 with less image size then it works fine.
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Re: Download offline maps

Postby Zax » 2017-11-18 4:16

Uday wrote:What I tried that select one resolution e.g 17 and it works , however sometimes it shows image error.
We can go to ''Options" at bottom and scroll option "Ignore Image Errors" and "Ignore Network Errors" it continues download with many failed images.


If the map provider is lack of some parts of the lv 17 map content, it would be recorded as a error during the downloading process. Anyway, these errors just indicate you that the data is not full, but it does not affect the actual usage.

The "Ignore XX Errors" options actually means "Do not pause the downloading if found any of these errors", but it still logged each error it encounter and report them to you just as a information, but does not mean this map could not be used.

More, the reason why lv 15 is OK and lv 17 is missing, is because higher resolution satellite imagery is much costly for both price and storage size, most map companies, even Google, may choose to only provide lv 15 for the whole world, lv 17 for most parts with human activities, and lv 20 only for big cities and hot areas.
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