TransDEM Forum https://forum.transdem.de/ |
|
Geo Data - USA https://forum.transdem.de/viewtopic.php?f=8&t=20 |
Page 3 of 5 |
Author: | geophil [ 22 Dec 2012 15:28 ] |
Post subject: | Re: Geo Data - USA |
After the changes of Dec 18, 2012, GeoTIFF is no longer available for 1 and 1/3 arc sec NED DEM. From now on and until the next change, "Arc Grid" (aka ESRI Binary Grid) is the choice for TransDEM. Please note that your need TransDEM 2.3.1 to open DEM files in this format. To obtain NED DEMs follow these steps:
|
Author: | SharkNose [ 08 Jan 2013 14:01 ] |
Post subject: | Re: Geo Data - USA |
When doing this on the Langhorne, PA huge DEM, I received a purely orange display where the DEM should have been in TransDEM. I thought it was a bad DEM and hated to have to try and download the ~400 MB again, but I zoomed in twice and the terrain appeared. These huge files are bad and good in some ways. With just one download, I can now lays tracks over 1/2 of New Jersey! Andrew |
Author: | geophil [ 08 Jan 2013 14:27 ] |
Post subject: | Re: Geo Data - USA |
When TransDEM displays that big orange plain, do a right click and check min and max elevation. It could be a void point which is not detected correctly and may be shown as a very low (negative) elevation. It that's the case, try to zoom in to a smaller area, pan around and watch the display for hopefully showing more than a single colour. |
Author: | SharkNose [ 09 Jan 2013 00:59 ] |
Post subject: | Re: Geo Data - USA |
Here's a seriously deep trench! But where is it? Can't see it from the screen, but panning a little North shows the New Jersey coastline: Found the same area in Google Earth: Coincidentally, that part of the New Jersey coast was one of the hardest hit areas during Hurricane Sandy last October! Obviously there are no rail lines there, but will this situation prevent me from creating a valid route in Trainz of another part of that DEM? Thanks. Regards, Andrew |
Author: | geophil [ 09 Jan 2013 10:33 ] |
Post subject: | Re: Geo Data - USA |
geophil wrote: Obviously there are no rail lines there, but will this situation prevent me from creating a valid route in Trainz of another part of that DEM? No, the DEM should be okay apart from the fault(y) area. You can either crop the DEM and reduce to valid regions or try to isolate those minima and replace them with valid values. Now, -2147483648 decimal integer converts to 80000000 hex in a 32bit double word and such a pattern is usually a placeholder for a so-called "void" point, an undefined elevation. Most DEM formats have a definition for such void points. In the case of ESRI Binary Grid and usage by USGS there appears to be a mixture of floating point and integer representations in the file which may cause confusion. I will have a closer look at that. |
Author: | geophil [ 13 Jan 2013 19:32 ] |
Post subject: | Re: Geo Data - USA |
TransDEM update 2.3.1.2: I have added more filters to detect invalid values. The USGS seem to have their own way of coding these. Looks okay now. |
Author: | SharkNose [ 13 Jan 2013 22:50 ] |
Post subject: | Re: Geo Data - USA |
Yep, I re-imported the raw DEM from the examples above into the newest version of TransDEM and the whole DEM showed with proper colors and elevations. Thanks for the update! Andrew |
Author: | mrgisa [ 15 Jan 2013 03:16 ] |
Post subject: | Re: Geo Data - USA |
Just a heads-up for those who are outside of the States and who are having troubles accessing the site: you'll need to enable English-US in your language settings. Details here: http://viewer.nationalmap.gov/help/index.php?faqID=162 Otherwise, it won't load up for you. Hope this prevents some hair pulling... |
Author: | Green Eggs n Pelham [ 16 Jul 2013 22:55 ] |
Post subject: | Re: Geo Data - USA |
This may sound like an overly simplistic question, but after zooming in on the area you want, do you simply select how many of the 1x1 boxes you want your route to cover? Either I read the tutorial wrong, or I read it too fast and missed a step somewhere between zooming in and selecting what you want. Thanks again! -A |
Author: | Jerker [ 17 Jul 2013 02:00 ] |
Post subject: | Re: Geo Data - USA |
G'day Green Eggs in Pelham, ...if I recall correctly, "-A", that is all you have to do, Once you select an area, it remains 'chosen' (highlighted, so you know you have already selected it) and when you move on to the next step, all of the areas you have selected appear in the list for the download process. Personally, I prefer to use the bounding box method but even then, the website's output seems to be, oddly enough, to provide the full 1° x 1° tiles that 'cover' the selected 'box' (rather than just the specified area)... Jerker {:)} |
Page 3 of 5 | All times are UTC + 1 hour |
Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |