Message Areas - "TsTools and the DEM question"

Train-Sim.Com Message Areas

"TsTools and the DEM question"

Email this topic to a friend
Printer-friendly version of this topic
Bookmark this topic (Registered users only)
Previous Topic | Next Topic Conferences MSTS Route Design (Protected) Original message
dcm (44 posts)
Dec-12-01, 09:06 AM (EST) "TsTools and the DEM question" Hi all,I'm posting this to clarify the current position of TsTools with regard to DEM file import. The following will be added to the next version of the userguide. Notwithstanding the below, we will definitely be introducing the SDTS import in time for the final release of version 1 in January.The default DEM type which can be imported into TsTools is a lat/lon raster grid with binary elevation values in meters stored as either 16 bit or 32 bit integer values.The data should be arranged in row major format with no header information, simply a raster image of data values.This type of data matches the GLOBE format which is available free for the whole world from the following location: http://ngdc.noaa.gov/cgi-bin/seg/ff/nph-newform.pl/seg/topo/customdatacdFrom this page you should select the area that you wish to cover, and then select the format of the data. The important fields in the data selection are:Data Type: set this to int16
File Format: pc binaryOnce your data has been downloaded, you will have three files. The *.bin file is the actual data file, the other file which you will need to refer to is the 8.hdr file which contains the header information.This data can be used in the terraform process in TsTools, or it can be loaded as a background bitmap by selecting Background Bitmap->From DEM. In order to select the correct DEM format, select the first option from the DEM selector dialog and the Topo Details Dialog will be displayed.In the filename field, select the *.bin file that you have downloaded.
In the four lat/lon fields enter the values as found in the header file (left and right, upper and lower x and y values). In the resolution field enter the grid_size value from the header file (usually 0.0083333333). In the selection box, select int16. In the null value field enter the value listed as elev_m_missing_flag in the header file. This is usually -500.Click OK and the data will be imported.
The major disadvantage of using the GLOBE data to terraform from is its low resolution. 0.00833333 degrees is 30 arcseconds (nearly 1 km at 50 degrees latitude). Although TsTools resamples the data to 8m resolution, this process can never add detail that it has no knowledge of, it can only ever smooth out the land between the known altitude points.For this reason, given that in Europe there is no higher resolution data freely available, we have used and got very good results from the following approach to terraforming in TsTools:- The Globe Data is imported as a background bitmap to give an instant overview of the topography across the map. - With reference to maps of the area, contours are drawn in TsTools using the imported DEM background as a guide to the lie of the land (this can make things much faster than trying to copy contours from maps alone)- Once the contours are complete, set up the chosen sample parameters and run Generate Sample Data - the imported DEM background will be replaced by the image generated from the contours you have drawn.- You can then refine this map by adding extra interim contours to highlight specific features, or to pull valleys or hills into sharper definition. - You can repeat this process of adding contours, generating sample data until you are happy with the background image generated - then you can terraform directly from the generated contour data.
Of course, this process would not be necessary if there was better access to high resolution DEM files. We are working currently to add a conversion routine which will read the SDTS DEM datasets which are available at high resolution for the US. But we would also like to hear of any other DEM formats (along with references for the download/purchase of data and file format) that anyone would like us to include.One quick final word about the XYZ import in the current beta - it is probably not a good idea to try it out yet. As stated in the release notes this was added at the last moment and not tested. The current routine takes a very long time to read the data and gives no indication as to whether it is working or has hung. You can try it, but you have been warned. Alert Edit | Reply | Reply With Quote | Top
Table of Contents

Subject Author Message Date ID RE: TsTools and the DEM question LawrenceKellie Dec-12-01 1 RE: TsTools and the DEM question dcm Dec-12-01 2 RE: TsTools and the DEM question LawrenceKellie Dec-12-01 3

Lobby | Topics | Previous Topic | Next Topic
Messages in this topic
LawrenceKellie (946 posts)
Dec-12-01, 03:32 PM (EST) 1. "RE: TsTools and the DEM question" I want to go on public record in affirming Dave and his team. I have been quite happy at the speed with which they respond to questions. I really have appreciated it.Lawrence Remove | Alert Edit | Reply | Reply With Quote | Top
dcm (44 posts)
Dec-12-01, 07:40 PM (EST) 2. "RE: TsTools and the DEM question" Thanks for your support Lawrence. And thanks also for the well constructed and documented descriptions of problems and questions encountered - that does help us to get things resolved more quickly. This last point goes out to others who have raised questions as well, thanks for not making me have to ask for extra information in order to solve problems.I know that a few people have encountered an error message intermittantly appearing if you switch projections or try to load a very large (geographically) route. This was due to (a) TsTools not resetting the zoom level to allow for the fact that a different projection may cause the Map to be physically too large and (b) TsTools initially loading a map with a default zoom regardless of the size of the map. We have already fixed these and I'll wait a couple of days to see if there are any more bits to fix, then I'll upload a patch.Thanks,Dave C. Remove | Alert Edit | Reply | Reply With Quote | Top
LawrenceKellie (946 posts)
Dec-12-01, 10:20 PM (EST) 3. "RE: TsTools and the DEM question" Correction on the URL you list for the National Geophysical Data Center:http://www.ngdc.noaa.gov/cgi-bin/seg/ff/nph-newform.pl/seg/topo/customdatacdIt appears to be just missing the "www" at the beginning.Lawrence Remove | Alert Edit | Reply | Reply With Quote | Top

Lock | Archive | Remove

Lobby | Topics | Previous Topic | Next Topic