Question on DEM..

[davidpaulsmith]

Hi. I was wanting to know if there was ANY way to figure out what sections one needs to download from the GIS Data Depot WITHOUT having to download the whole county, just to do the rail line.
I did a search but didn't get any results.

Hope that makes sense

David

 

[Dermmy]

The second last post in this thread might help...

Andy

 

[RPearson]

Not sure I follow you David. On the GIS data depot free TIGER data is offered on a county wide basis only. Seperate version are available by the year data was developed. A single zip file holds all the TIGER data files for the county for that year. Within the zip are a primary file (with .r1 extension iirc) and several secondary files. The primary file holds the data for the start of each line segment for all categories. The .r2 file holds the continuation of the line data. The file formats can be found here: http://www.census.gov/geo/www/tiger/tiger2k/tiger2k.pdf

The vector data for various road types and stream is very useful if you're duplicating a specific route and it's all contained in a single zip file. Files .r1 and .r2 (record types 1 and 2) hold all the line data - rr, roads, streams, etc.

Bob Pearson

Edited to correct an aging memory.

 

[Tokkyu40]

It's easy (after Dermmy showed me)

Go to Dermmy's post near the bottom of the page he linked to, follow his link to the National map viewer, set it up as he explains and note the names of the regions that your rails run through.
Go to the data depot and download the DEMs for those regions, plus TIGER data for the counties involved.
Then go wild.
It's actually kind of fun to open Trainz and see the rolling landscape all around you. Just remember, it does very poorly at reproducing cuts and berms, so you'll have to watch for that when you build the track.

Claude

 

[geophil]

To reiterate, for the more ambitious US route builder:

The Trainz baseboard raster is 10 meters. Obviously, the most suitable DEM for this is one with a resolution of 10 meters or 1/3 arc sec. The USGS happens to provide such DEMs with increasing coverage of the contiguous United States. Thes DEMs are also free. Download them from USGS Seamless Server.
http://seamless.usgs.gov/website/seamless/

For 10 m DEMs TIGER data is no real match. TIGER specs say, accuracy is based on a scale of 1:160000. Have a look at 1:24000 USGS topomaps instead. Available online from MS Terra Server and at least one other source. MS Terra Server also offers a WMS interface for automated download with a WMS client.
http://www.terraserverusa.com
WMS:
http://terraservice.net/ogccapabilities.ashx
http://terraservice.net/ogcmap.ashx

geophil