Please login or register.

Login with username, password and session length

News:

Registration is only required if you want to post, and is not needed to read any posts. To avoid excess 'spam' accounts, all accounts where no posts have been made will be deleted after two weeks. Please register again if you wish to post.

Author Topic: World Model Creation  (Read 8984 times)

October 27, 2011, 10:24:04 AM
  • Member
  • **
  • Posts: 2
    • View Profile
Hi, I have just found Bridge Command and I am eager to create a world model.

I understand the requirements from the docs, but I need to know what software to use to create the world files.
I am presuming that SRTM data will be used. Can someone enlighten me about the actual proceedure of the creation of the variose BMP files needed.

Thanks,

Marvin.

October 28, 2011, 09:34:18 PM
Reply #1
  • Administrator
  • Member
  • *****
  • Posts: 89
    • View Profile
Hi Marvin,

Yes, one of the main sources of data for elevation maps is SRTM data, which can be downloaded from http://earthexplorer.usgs.gov/. In addition, for the USA, the NGDC Coastal Relief Model (http://ngdc.noaa.gov/mgg/coastal/startcrm.htm) is a very good data set which combines land elevation with sub-sea bathymetry for the US continental shelf.

Since I have last worked with these data sets, the data formats available have changed, so I need to investigate further what tools are available to convert the data into BMP format, suitable to load into Bridge Command. I will look into this over the weekend and post an update here.

In the UK, the Ordnance Survey have recently released a reasonably high resolution digital elevation map (Land-Form PANORAMA on https://www.ordnancesurvey.co.uk/opendatadownload/products.html) under their OpenData licence. However, this is referenced to the UK National Grid, so I am currently looking at how to re-process this into a latitude/longitude format using WGS84, the standard datum used by modern charts and gps.

Once you have your heightmap in an image format, you can also generate a texture image to display on the terrain when it is loaded in the program, which should be the same image size as the heightmap. For this I currently use L3DT (http://www.bundysoft.com/L3DT/).

The radar image file is now only used as a map in the scenario editor and map controller, as the radar image is simulated directly from the terrain. Therefore I normally use the same image as the land texture.

I will report back on tools to convert the available datasets into a bitmap image,

James Packer

October 29, 2011, 10:30:59 PM
Reply #2
  • Administrator
  • Member
  • *****
  • Posts: 89
    • View Profile
To follow up:

The best data source for importing STRM data for terrain models appears to be CGIAR, who maintain an SRTM dataset with voids filled in (http://srtm.csi.cgiar.org).

I have also put together a tool to convert this data from ArcInfo ASCII format into an image format suitable to generate a heightmap for Bridge Command. This creates a 'pgm' file, which can be read in a good image editor, such as the free GIMP (http://www.gimp.org/downloads/), and saved as a .bmp or jpeg file.

To use this data to generate a height map image:
>Go to: http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp and select the area you want.
>Select 'ArcInfo ASCII' as the file format
>Search and download the data you want

>Download the conversion tool from http://www.bridgecommand.co.uk/file/import.exe
>Save import.exe somewhere
>Drag and drop the .asc file you have downloaded with your data onto the import.exe program file
>Set the sea depth when requested (SRTM has no sub-sea data)
>The program will process the file, which will take a number of minutes, and may appear to freeze while writing the output file
>When done, the output file will be saved in the same location as the input, with .pgm appended to the filename. Note the TerrainMaxHeight and SeaMaxDepth values to use.
>Open the .pgm file in your image editor, and follow the documentation to save this in the correct size as a .bmp or .jpg file.

Please note the terms of use of the CGIAR data at http://srtm.csi.cgiar.org/SELECTION/SRT_disclaimer.htm.

Please let me know if this is helpful, or if you come across any issues,

James Packer

October 30, 2011, 10:30:52 AM
Reply #3
  • Member
  • **
  • Posts: 2
    • View Profile
Meny thanks, James.
That is a great help!!

I will let you know how I get on.


Marvin.

May 28, 2014, 11:32:38 PM
Reply #4
  • Member
  • **
  • Posts: 10
    • View Profile


"Once you have your heightmap in an image format, you can also generate a texture image to display on the terrain when it is loaded in the program, which should be the same image size as the heightmap. For this I currently use L3DT (http://www.bundysoft.com/L3DT/). "

Hello Might you explain how the program L3TD is used to generate the field, I fail to understand how to use it from the map image. i have a image in BMP or JPG downloaded and i have the importe.exe image.

Thanks

June 18, 2014, 02:51:12 PM
Reply #5
  • Administrator
  • Member
  • *****
  • Posts: 89
    • View Profile

April 19, 2015, 06:13:25 PM
Reply #6
  • Member
  • **
  • Posts: 3
    • View Profile
Ok, am doing Kingston Ontario Harbour, almost got it done but the world is too big. I am having trouble with the Lat Long extent. What exactly is this supposed to be? I am about 40 minutes either side of my bottem left corner. Cheers
Mark

November 06, 2017, 11:21:56 PM
Reply #7
  • Member
  • **
  • Posts: 27
  • Officer of the Watch Deck
    • View Profile
where can the tool for converting .asc to .pgm be downloaded from ?

November 14, 2017, 08:15:36 AM
Reply #8
  • Administrator
  • Member
  • *****
  • Posts: 89
    • View Profile
Hi, I use the script in post https://www.bridgecommand.co.uk/forum/index.php/topic,1729.msg2033.html#msg2033, and run this with GNU Octave, an open source numerical processing program, available from https://www.gnu.org/software/octave/#install