Author Topic: Downloading a map where area is defined by pre-drawn contours  (Read 216 times)

Offline Bosanek

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Hello!

Sometimes I use the function to download a map for offline use. I usually use that for remote islands for example, which typically have irregular shapes.

In order to minimize download size (tile count, bandwidth use, storage memory use), I strive to define the map area to be as close to the shape of the island as possible (i.e. to exclude as much surrounding water surface area as possible).

I also have the need to download the same area in two or three map types (in separate SQL files of course), because a single map type can rarely provide me with all the information which I need there.


The problem is that it is rather tedious work to define the download area in such a precise irregular shape by dragging around so many points on a tablet's touch screen.
What's worse, I have to define the SAME area again from scratch when downloading the next map type for the same island!


Now, I have two questions:

1.
Is it possible to do a map download, where the download area would be predefined from an existing source (which could for example exist as a KML "path"/track)? The KML path would be a closed-circle path (of irregular shape), and the download area would be everything inside that circle.

2.
Is it somehow possible to download another map with the download area defined by the area from a particular (different) offline map SQL file? That way I could download another map of the same place without having to re-draw the area manually again.


I hope that I made these issues clear.

Kind regards!
 

Offline menion

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #1 on: April 13, 2017, 14:10:30 »
Good day Bosanek,

option no. 2 is not possible, but the first definitely is.

Please check our manual: http://docs.locusmap.eu/doku.php?id=manual:user_guide:maps_download#download_launch , there is an option to download area defined "by track", which is what you need.
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Offline Bosanek

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #2 on: April 13, 2017, 15:27:17 »
Thank you for a prompt reply.

I had already investigated the option of downloading a map "by track" ("Select a track" function, available only in Locus Pro).

However, if I understand that function correctly, the download area will be the surround of the track lines. In my case, if the track is roughly the coastline of an island (an irregular circle), the downloaded are in this case would be a "donut", encompassing island's coastline and a lot of sea around it. It would not include the inland area of the island.


Please correct me if I am wrong on this one! It would be ideal if this function would work, but to treat the track as closed outline of the area to be downloaded.


Is there any other way to download several maps with exactly the same area shape definition (not having to draw the area manually each time)?
 

Offline menion

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #3 on: April 13, 2017, 16:04:44 »
Hello,
excuse me, I'm stupid. You are correct. Unfortunately this option does not yet exists.

As I was able to found, only idea related to this topic is this: http://help.locusmap.eu/topic/remember-previous-settings-when-downloading-maps , so it looks for me there is not much people interested in such kind of downloading. Sorry.
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Offline Bosanek

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #4 on: April 13, 2017, 16:26:39 »
So I am currently out of solutions with my problems?

Could this be turned into a "feature request"?
At least the option to "download by track", where the track would represent the outline of the download area. It does not sound complicated to do, since most of the code for the functionality appears to already be in the program.

I would not mind to have it as a "pro" feature.

Even if this feature request would be incorporated, how much time would I need to wait (weeks, months, eons ...)?

Kind regards!
 

Offline michaelbechtold

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #5 on: April 13, 2017, 19:33:52 »
Vector maps with different themes - that would fly if the maps you are using do not use other sources than OSM.

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Offline michaelbechtold

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #6 on: April 13, 2017, 19:40:45 »
Map 'download by points' can help, too. You need to set a number of points inside the island, define the radius and at least have a consistent outline for the various map types you need. You can also start with the outlining KML, use some scripting or Excel to fill the inner part. I.e. automate the 'by point' method.

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Offline Bosanek

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #7 on: April 17, 2017, 11:13:16 »
Thank you for the idea.

The idea of semi-automating the "by points" download method does have some potential (given the current limited options).
It still involves a lot of manual work, including dedicated coding.

It's better than nothing, but still much worse than any of the proposed feature requests.

 

Offline michaelbechtold

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #8 on: April 17, 2017, 20:48:47 »
Some coding is under (y)our control, Menion's priorities are not ...
 

Offline john_percy

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #9 on: April 17, 2017, 22:07:34 »
As a matter of interest, do areas of uniform sea add significantly to the map file size? I would have thought that any reasonably efficient compression would mean they made little difference to the overall file size.

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Offline michaelbechtold

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Re: Downloading a map where area is defined by pre-drawn contours
« Reply #10 on: April 19, 2017, 17:58:27 »
1-2k per tile, I saw in some sqlite DBs.