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 Post subject: Indonesian DEM
PostPosted: 03 Aug 2023 11:34 
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Joined: 05 Jan 2011 16:45
Posts: 1463
Aprinto wrote:
After TIF merged is about 2GBs size.
That explains it.

Aprinto wrote:
Here link about Indonesian DEM :
https://tanahair.indonesia.go.id/demnas

Here link of sample what I donwloaded and translated to WGS84 EPSG:4326
https://drive.google.com/drive/folders/ ... sp=sharing
Thanks very much, that looks promising. I will start analysing there in a couple of days.


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 Post subject: Re: Newbie problems
PostPosted: 03 Aug 2023 12:14 
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Joined: 02 Aug 2023 03:29
Posts: 6
Oh sorry again... I forgot again ....

The step I did was :
- Download original TIF
- Raster calculation to adjust to +3.75m to set that sea level is 0.
- Translate to WGS84 EPSG : 4326

Then finally
- Convert TIF to DEM in TransDEM ...


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 Post subject: Re: Indonesian DEM
PostPosted: 07 Aug 2023 17:35 
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Joined: 05 Jan 2011 16:45
Posts: 1463
I think I've got it working. DEMNAS is provided in GeoTIFF format, but comes with the absolute minimum of meta data. TransDEM until now expects more information here. I will change that and make the GeoTIFF reader more tolerant. If the model meta data is missing I will assume a geographic model with latitude and longitude, spacing in degrees and elevations in metres. This appears to be correct for the DEMNAS data. Here is an example:

Image

@Aprinto: Any idea why sea level is not 0?


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 Post subject: Re: Indonesian DEM
PostPosted: 08 Aug 2023 04:00 
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Joined: 02 Aug 2023 03:29
Posts: 6
geophil wrote:
@Aprinto: Any idea why sea level is not 0?


I am not topo expert, just for fun to try more accurate topo for Trainz.
I compare between TransDEM and the reality is. I am not wish to 100% accurate.

There is a real station altitude near the ferry port called STATION MERAK. It's have +3.00m height above sea level, official sign board.
https://upload.wikimedia.org/wikipedia/ ... _Merak.jpg

But in DEMNAS_1110-22, DEMNAS_1110-31 or DEMNAS_1109-54 (one of them), the sea level is -3.75m and the station is 0m.
So I assume all DEMNAS need to adjust +3.75m

But now, I give up. I will use original data I downloaded.

geophil wrote:
I think I've got it working. DEMNAS is provided in GeoTIFF format, but comes with the absolute minimum of meta data. TransDEM until now expects more information here.


So this is why TRANSDEM could not open DEMNAS which based on EGM2008 (EPSG:8355 ???) as they said. TransDEM only give "error opening file". Some site informed me that DEMNAS will upgrade to EGM2020 ...

QGIS 3.32.1 Lima can open this EGM2008 file. So I should convert first to WGS84 before open in TransDEM (without adjust the height).
I hope TransDEM able to open DEMNAS directly without QGIS convertion again.

But thanks Geophil...
I very appreciate your work.


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 Post subject: Re: Indonesian DEM
PostPosted: 08 Aug 2023 13:42 
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Joined: 05 Jan 2011 16:45
Posts: 1463
Aprinto wrote:
So this is why TRANSDEM could not open DEMNAS which based on EGM2008 (EPSG:8355 ???) as they said. TransDEM only give "error opening file".
The reason why TIFF for raster data is quite popular is its flexibility. Part of this flexibility is the meta data. You express many aspects with TIFF meta tags. GeoTIFF is an extension to TIFF, simply by defining a bunch of additional meta tags that make sense for geo data, most of them to allow and facilitate georeferencing.

There are a couple of GeoTIFF meta tags that you would normally expect and which don't have defaults. TransDEM aborted, because the most fundamental of them, GTModelType, is missing in the DEMNAS .tif. The model type is either "projected", "geographic" or "geocentric". (Luckily, I never came across "geocentric".) And all the other tags, that further refine the model, are also missing. The only GeoTIFF tags present are the "tie points" which define the coordinate origin of the data and the "spacing" which defines the size of a pixel in applicable geo coordinates.

So, I invented my own defaults to deal with DEMNAS. I hope this won't have any unwanted side effects.

Interestingly, the Earth Gravitational Model (EGM) is not even represented in the standard set of GeoTIFF tags, presumably as it does not affect the model and the data. Nonetheless, I guess it plays an important role in geo data for Indonesia, as this is a very active tectonic region.

Aprinto wrote:
But in DEMNAS_1110-22, DEMNAS_1110-31 or DEMNAS_1109-54 (one of them), the sea level is -3.75m
Mine is the same. There must be a reason for this.

The simplest way to raise or lower the entire DEM in TransDEM is to place a single control point anywhere onto the DEM, set its mode to relative and set the adjustment value, then apply. We can't do centimetres, though.


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 Post subject: Re: Indonesian DEM
PostPosted: 03 Sep 2023 13:09 
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Joined: 02 Aug 2023 03:29
Posts: 6
Hi Geophill,

I posted here because not possible to reply your annoucement about new update to TransDEM 2.6.6.1

After I update, TransDEM now able to open Indonesian DEMNAS. It was success to open original file I downloaded.

BUT, when I want to EXPORT DEM and texture to TRAINZ, there's error looks like "Error exporting raster map" as TransDEM 2.6.6 do it well ...
I don't know why ... So at this moment, I go back to downgrade to previous version 2.6.6...

Cheers,
Aprinto


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 Post subject: Re: Indonesian DEM
PostPosted: 03 Sep 2023 13:35 
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Joined: 05 Jan 2011 16:45
Posts: 1463
I did not touch any of the Trainz export functions for 2.6.6.1 and no one else has reported an export problem so far. I need more information of what geo data you have loaded for this export.


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 Post subject: Re: Indonesian DEM
PostPosted: 03 Sep 2023 14:35 
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Joined: 02 Aug 2023 03:29
Posts: 6
geophil wrote:
I did not touch any of the Trainz export functions for 2.6.6.1 and no one else has reported an export problem so far. I need more information of what geo data you have loaded for this export.


I apologize for wasting your time....

After downgrade to 2.6.6 and then update to 2.6.6.1 again (but now UNCHECK update MS RUNTIME) :

- ORIGINAL geotiff DEMNAS, success to convert to dem, BUT STILL NOT POSSIBLE to add next dem files ("DEM operation aborted")
- Converted geotiff DEMNAS (QGIS GDAL), success to convert to dem now success to export to TRAINZ ...

I don't understand with this anomali ...

I had success to export ENTIRE JAVA ISLAND route from western to eastern (to Bali).
The distance between west and east is about 1000 km.
Filesize total is about 8gigs, need 12 hours to export process ....

Image


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 Post subject: Re: Indonesian DEM
PostPosted: 03 Sep 2023 15:04 
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Joined: 05 Jan 2011 16:45
Posts: 1463
Aprinto wrote:
ORIGINAL geotiff DEMNAS, success to convert to dem, BUT STILL NOT POSSIBLE to add next dem files ("DEM operation aborted")
Out of memory? What grid width did you use?

Image:
Quote:
https://drive.google.com/file/d/1Bef8LwYk55T8YbqdIE3432yX3LAcVTzb/view?usp=drive_link
That's quite impressive!


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