Getting the coordinates of a "line"

General talk
1

Hi list!

I’m not really sure, I’m right here, but maybe can someone give me a tip…

So, I have a map as PNG (see https://www.dwd.de/DE/fachnutzer/luftfahrt/teaser/gafor_test/luftsportberichte_mit_bild.html). In this file (for example German map) there are many regions. For all pilots, I’m speaking about GAFOR region.

I’d like to draw these regions in an App I’m writing and that uses OSM-data. Of course, I need the “coordinates of the lines” for all these regions, but I don’t have any idea, how to get them…

I’m pretty sure, there exist many programs to georeference an image and select lines to get the coordinates, but this is a new world for me, so I don’t know how to solve my problem.

Can someone help me?

Thanks
Luca Bertoncello

2

Maybe try https://geojson.io/ where you can draw Lines and polygons on an OSM based zommable map.

As a result you get angeojson file that contains the coordinates.

Success?

3

Thank you for your suggestion.
Of course, I can use this site to create a polyline, but my problem is to do that “on the lines of the PNG”…
Unfortunately, I cannot add an image to the map to “draw on the image”.

Any other idea?

Thanks
Luca

4

You can have any image file as an background image in JOSM with plugin PicLayer.

5

Can you explain me how to do that?
I’m really new in this process and don’t have any idea which program I can use and how…

Thank
Luca

6

The plug in is used with JOSM editor.
The osm wiki has a page about PicLayer:

https://wiki.openstreetmap.org/wiki/JOSM/Plugins/PicLayer

I have used the plugin a couple of times, and I’m not expert on it.
It takes some time before you get used to the commands of how to align the custom image.

7

If you don’t have used the stand alone JOSM editor before, there is a learning curve.
The first step is learning how to use the editor to do “normal” changes.
Then when you understand how to enter roads, buildings to OSM, you can try the PicLayer.

I don’t know if the more popular web editor (ID) has any functions to do what you want.

8

OK, so if I understand correctly, I have to download the josm.jar and install the plugin. No problem.
But I always don’t have any idea how to use it.

As I sayd, I just need to create some polylines to define the regions. Maybe can someone give me a little howto?

Thanks a lot
Luca

9

Yes, the first step is to install JOSM.

If you have windows there is an windows installer:
https://josm.openstreetmap.de/download/windows/josm-setup.exe
(on page https://josm.openstreetmap.de/wiki/Download))

But as you don’t have used JOSM before, there are no quick fixes to your problem.
I recommend to go the (long) way of first learning how to use JOSM, before trying the plugin.

Also browse the osm wiki which have lot of useful information.

Take your time!

10

OK, I’ll try it…
Currently I downloaded the JAR file (I’m using Linux) and I can start it.
Unfortunately, if I try to download the “region” for Germany, I get the error, that this is too big. Any idea how to “increase the max data”?

Thanks
Luca

11

Drawing lines and areas are done with “Draw node” tool (short key A). You click and draw node (points for the line). Then you have to set tags on the line. Depending what the line represent. There are lot of options here. All this is basic knowledge you have to know, when you are using JOSM.

12

When you download you draw a bounding box. If the box is to big, you have to decrease the size of the box.

A bigger area can then be download to the same layer by doing several smaller download of different parts of the big area.

13

Have you tried using a georeferencing tool to extract the coordinates of the regions in your PNG map? This can help you draw the regions in your app. If you’re new to this, perhaps you can explore some popular programs for georeferencing images and selecting lines to get the coordinates.