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 Post subject: Tutorial by a Newbie :)
PostPosted: 26 Aug 2020 18:01 
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Joined: 21 Aug 2020 04:13
Posts: 33
So if the title didn't get your attention, keep in mind I have only been back in Trainz (specifically TRS19) for about 4 to 5 months. Transdem I believe it's been 1 to 2 weeks. For the most part I'm learning as I go and finding a system that works for me.

Start small! That doesn't mean you route has to be limited to a small area necessarily, just work on small areas at a time. You can still get a large route functional within a reasonable amount of time to operate and add the details later.

I already had about 20 mainline miles down in the Basemapz approach but a gift of a DEM file eventually lead me to wanting more and my purchase for Transdem has been worth every penny.

You can get plenty of detail in the UTM overlay files. I thought Google Earth was the only option, but Bing does a good job. Fort Erie which I'm starting at vs Port Robinson in my 1st route can handle both Level 19 and 20 UTM from Bing. However since 20 is not available everywhere I settled with 19. I was able to obtain in Canada 15M data from the government for free. the nearby United States USGS has 5 and 10M data depending on the area. It even includes, some but not all of my area.

Here I am in the 15M data and I'm right at the border with the U.S. Now this adds some complication which I plan on fixing tonight. But thankfully the border is in the Niagara River which is at an absolute height that is easy to fix with the fill technique.

I was able to load the entire raster images (all 400 that I downloaded the night prior as it will save the georef to 1 file). Here I demonstrate also why I like to start slow. The bigger amount of data, the more risk you are to errors in processing.

Here is the video

https://www.youtube.com/watch?v=vqUH-Jbqtk0

I continue to do more on YouTube every night.

Thanks

Sean


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PostPosted: 29 Aug 2020 10:48 
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Joined: 05 Jan 2011 16:45
Posts: 1463
Sean,

you are showing a few DEMs in TransDEM which are predominantly rendered in an orange colour. Orange may indicate "invalid" here. Depending on the DEM data source and file format, TransDEM should automatically recognize the invalid points and ignore them. But not so in your examples. Can you tell me where these particular DEMs originate from?

On raster maps, acquired via the Map Tile client along a path: These will always come with an additional list file .lgb which will indeed reference the entire bunch, as you already figured out. And yes, it's in the manual.

Keep in mind that TransDEM keeps all loaded geo data in memory, so for lots of raster maps/images or large hi-res DEM, you may exceed the physical memory installed on your system and even virtual memory. Exceeding physical memory will make TransDEM (and all other applications) very slow, exceeding virtual memory should trigger an error and abort. But not all cases can be caught so it may crash the application without an error message, unfortunately.


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PostPosted: 31 Aug 2020 12:53 
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Joined: 21 Aug 2020 04:13
Posts: 33
Actually I've been able to figure out what that is. The Canadian data for some reason starts showing data at the border of -32767 but it slopes towards it. I believe that is the software creating the slope as per design. I've been able to use the triangular control points, delete, then fill to an absolute value to fix. Fortunately for me it's a bit easier because the US Canada border is on water here.

I have been able to also Add in USGS images that run along the border and even into Canada further north. I'm taking my time now with how many images I put in play. Of course having a huge DEM is probably not as wise as doing them in segments. I may split some areas up again.

I believe I've seen a message when adding images about limitation or something so it only will do so many UTC tiles anyways. I just crop what I need and add them in slowly. The manual has been a great help as I'm starting to understand what everything means. Memory (of the brain) is not my strong suit, but working through the issues and repetition will enforce the new skills.

Thanks

Sean


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PostPosted: 01 Sep 2020 09:18 
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Joined: 05 Jan 2011 16:45
Posts: 1463
Seane2c wrote:
Actually I've been able to figure out what that is. The Canadian data for some reason starts showing data at the border of -32767 but it slopes towards it.
The ESRI ASCII DEM file format has a header where one field indicates the invalid or void value. As DEMs are always arranged in 2-dimensional arrays, every index must be present and will have a value. TransDEM will filter out the invalid ones. -32767, -32768 or +32767 are typical placeholders here.

For this particular DEM source file, did TransDEM show this all-orange picture when opened the first time? If yes, this would mean that something went wrong with the invalid value detection.


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PostPosted: 01 Sep 2020 12:30 
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Joined: 21 Aug 2020 04:13
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It was 2 tone green and orange. Regardless I was able to repair it. I believe there was an area with ? as well on the U.S. side of the Canada data.

Thanks

Sean


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PostPosted: 01 Sep 2020 17:40 
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Joined: 05 Jan 2011 16:45
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Seane2c wrote:
It was 2 tone green and orange. Regardless I was able to repair it. I believe there was an area with ? as well on the U.S. side of the Canada data.
But it was a Canadian DEM? In .asc format?


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PostPosted: 08 Sep 2020 18:01 
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Joined: 21 Aug 2020 04:13
Posts: 33
I believe it was unless I found something better. I'll try and check my downloads when I get home to see if that is what I started with.

Whatever it was the border with the United States was coming up as null data. Not sure if it was trying to smooth. I believe it showed up as -32767 which I'm familiar as a programmer the 32768 number sounds like 8 (bytes) to the power of 5? or 16 bit in hex.

Thanks

Sean


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PostPosted: 08 Sep 2020 18:57 
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Joined: 05 Jan 2011 16:45
Posts: 1463
TransDEM is expected to remove all Elevations encoded with the "invalid" value when reading the file. This way the invalid values don't get mixed up with proper elevations. In you case something went wrong. And the explanation normally is that somehow the invalid values slipped through, either because the DEM meta data did not define them correctly or TransDEM did not recognize it as invalid. And I want to find out the cause of the problem. The "great orange void" simply should not happen.


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PostPosted: 11 Sep 2020 17:50 
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Joined: 21 Aug 2020 04:13
Posts: 33
Yeah it surprised me as well.

I don't have the files with me because again I'm at work. But if you look through the mapping service I live in an area on the Canada US border. It's Niagara home to Niagara Falls and lies between 2 of the 5 great lakes of North America Lake Erie and Lake Ontario. The border follows the Niagara River.

I would try downloading a sample which is free through the links provided to me here (I think). My memory is not always the greatest.

Let me know if that helps.

Thanks

Sean


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PostPosted: 11 Sep 2020 18:59 
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Joined: 05 Jan 2011 16:45
Posts: 1463
Seane2c wrote:
It's Niagara home to Niagara Falls and lies between 2 of the 5 great lakes of North America Lake Erie and Lake Ontario. The border follows the Niagara River.
No "luck" so far. Downloaded the Canadian part as ESRI ASCII grid. Proper invalid values for US and proper level for the two lakes. Did you merge it with US data?


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