Orienteering maps as custom maps

[Reino Ruotsalainen]

I want to use orienteering maps as custom maps and have not used this app yet. The maps are georeferenced and originally in OCAD vector format. They can be exported for example in png, jpg or GeoTiff. Thus no georeferencing is more needed. 

Can I omit georeferencing?

Typically the maps are quite large (>10-20 Mbytes).

Does this cause big problems?

Must I divide the maps in smaller parts?

[Tobias Ekman]

On Sunday, 8 December 2024 at 09:30:02 UTC+1 Reino Ruotsalainen wrote:

I want to use orienteering maps as custom maps and have not used this app yet. The maps are georeferenced and originally in OCAD vector format. They can be exported for example in png, jpg or GeoTiff. Thus no georeferencing is more needed. 

Can I omit georeferencing?

Custom Maps uses KML, more specific one <GroundOverlay> packed inte a KMZ file. According to:

https://maprunners.weebly.com/ocad-maps-and-courses.html

OCAD can export to KMZ and using the "No Tiles" setting it should work with Custom Maps. The size of the map image is only restricted by the memory available to Custom Maps on your phone.

[Reino Ruotsalainen]

Tobias gave a very good advice and I managed to load about 10 custom maps to the map directory using the real map names as file names. However, when I start using the maps, they are all listed using the same name "tile_0_0.jpg". This is quite confusing. I have to look at the map content, if it is the right one. May it be something wrong in KMZ-export from OCAD? 

Also when I try to load KMZ-file to Google Maps, some critical error will happen. Google Earth Pro will import these KMZ-files in correct way.

[Marko Teittinen]

Reino,

If you are creating the maps within Custom Maps, you should type in a descriptive name in the "Map name" field. If you are importing maps as .kmz files then you should make sure that the KML file inside the KMZ file contains a unique name (or at least description) for the map.

But since it sounds like you have already imported the maps into Custom Maps, you can "long-press" (press and hold) the map name in the list, select "Modify map", and then enter a new name (and description) for the map. You can save your changes by tapping the "preview" button and then "save".

Regarding the error that occurs loading the exported KMZ files to Google Maps, it is possible that Google Maps does not like the KML "GroundOverlay" tag. Another possibility is that Google Maps does not correctly ignore the KML extensions I use in the Custom Maps generated KML files. The extensions used by Custom Maps follow the KML specification for extensions, and as such any good KML parser should be able to ignore them. This is shown by Google Earth handling the Custom Maps generated KMZ files fine. KML and KMZ (zip file containing a KML file and resources) are the original data formats for Google Earth.

I'd like to add here also that Custom Maps does not implement a full KML markup parser/renderer. It ignores almost all other tags except GroundOverlay since it is not going to render the other stuff.

Marko Teittinen

Author of Custom Maps

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[Reino Ruotsalainen]

Thanks a lot - now it works well!

Reino

[Reino Ruotsalainen]

But still one problem: I have 10 Custom maps. The app shows only 8 of them under the title "Lähimmät kartat". How I can select the 9th map, which is far in the north?

[Reino Ruotsalainen]

My understanding from this was wrong. Custom Maps had not loaded the last 2 maps. I am using gdal for transformation from GeoTiff to KMZ like this

gdal_translate -scale -of KMLSUPEROVERLAY input.tif output.kmz

Of some reason Custom Maps cannot load the output KMZ.

However, I can open it in Google Earth Pro (desktop).

If somebody can guess, why Custom Maps will fail in loading, I would be very thankful.

Best Regards,

Reino

[Reino Ruotsalainen]

Still more detailed description of my process:

I have done a lot of tests to load KMZ-files to Custom Maps, but it will not load them.

My files have been prepared like this:

1)        The raster has been loaded in GeoTiff-format as raster layer to QGIS (coordinate system EPSG:4326-WGS84).

2)        Raster conversion Ground Overlay to GeoTIFF Image in QGIS.

3)        Raster conversion to KMZ-superoverlay using GDAL like this:

gdal_translate -of KMLSUPEROVERLAY C:/Users/35840/Documents/Overlay.tif C:/Users/35840/Documents/Overlay.kmz

4)        The result KMZ-file can be viewed in Google Earth without any problems.

5)        But when I try to load it to Custom Maps, it is not loaded.

What may be wrong in my process?

The original raster is a georeferenced orthophoto (2,6 Mbytes). KMZ-file is only 123 kbytes.

[Tobias Ekman]

On Tue, 31 Dec 2024, 10:38 Reino Ruotsalainen, <reino.ruo...@kolumbus.fi> wrote:

2)        Raster conversion Ground Overlay to Ge)        Raster conversion to KMZ-superoverlay using GDAL like this:

gdal_translate -of KMLSUPEROVERLAY C:/Users/35840/Documents/Overlay.tif C:/Users/35840/Documents/Overlay.kmz

The original raster is a georeferenced orthophoto (2,6 Mbytes). KMZ-file is only 123 kbytes.

Then GDAL has not created a KMZ file that Custom Maps can use. Unzip the file and compare the KML with the KML from a functioning KMZ map. The KML should contain a direct reference to the image in the "images" folder.

/Tobias

[Marko Teittinen]

Reino,

I believe the KML super overlay option creates multiple overlay images at different view levels. Custom Maps does not support complicated hierarchies of map imagery, just a single ground overlay image per file (it can actually handle a few images, but managing them becomes a hassle). But on the other hand, it can support pretty large images in those overlays (as large as your Android device can handle loaded in memory at once).

So if your software has an option of creating a KMZ file with just a single ground overlay image from your source image, things should work fine.

Marko Teittinen

Author of Custom Maps

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