Hi All

I am trying to find some DEM files to import for use as terrain, new to this so a few questions

1. Where do I find them?
2. How do you resize them to the correct size and keep the terrain correct?
3. I see you can also use a 'picture' to generate terrains to, where do you get them from?. That is the black and white pictures.

Thanks for any help as always

Attached Link: http://www.vterrain.org/Elevation/dem.html

Check out this site, I think there are some links to free ones but very few. I've yet to find a good source of free ones. If you need to purchase any, they're not cheap!!!

Attached Link: raster roam

**You might want to try this site. It can give all sorts of data based on long. and lat. I posted this in terragen as it output .ter but there are a wide range of out put formats to experiment with. I can only vouch for the .ter files as that's what I use but I feel certain there is something there that you can use/adapt.. ...**

thanks all, looking now

I remember there being some DEM files on the extra cd with VistaPro... if those are the same kind of file.

You can do it the following described way:

Go to the website:
seamless.usgs.gov/

There you can call up a US and a few whole world maps (mostly North America terrain in detail), a program opens up in your browser (it takes a moment to load the data), where you can find places through different search options for example  and use 'goto' at the bottom of the window from a list of found areas (There is a button 'Tutorial' for help).

img524.imageshack.us/img524/2271/usgs1kz4.jpg

You can use your mouse to draw a box around an area (be careful to check, you don't use a to big an area, but you can check later in the next windows appearing the size of the file and re-adjust your selected area again) or you can enter coordinates, or template selection.

img411.imageshack.us/img411/8859/usgs2uf3.jpg

Then the 'Request Summary Page' appears telling you, what area you've grabbed, the size in MB and the download button for this area. But that's not what you want, yet.
You click on 'Modify Data Request' .

img405.imageshack.us/img405/2995/usgs3sn6.jpg

There you scroll all the way down to the bottom of the list and select 'GeoTIFF', where it says 'ArchGRID'. Then push 'Save Changes & Return to Summary' button.

img524.imageshack.us/img524/5049/usgs4gb1.jpg

It will return to the summary window - then push 'Download' - another window appears telling you the data will be prepared and at the end of the process you can download the zipped data.
img524.imageshack.us/img524/6420/usgs5mj4.jpg

What you get is a 'NED-.....'  zip-file. Open it and extract the large *.tif image.

Now go to:
www.visualizationsoftware.com/3dem.html
and download this '3DEM' converter program and install it. You can use this program from now on to convert the GeoTIFF images into DEM-files or other files to be used in Terragen for example - just read the info on this website. The program itself is pretty simple to use.

img524.imageshack.us/img524/9592/3demls5.jpg

Starting the program a selection window appears, where 3DEM wants to know, what data you will be working with - click on 'GeoTIFF' and then load your GeoTIFF file.
The terrain will be displayed, in 2D or 3D (the square box area on the map will be calculated in 3D - you can move it around on the terrain-map) if you want.

Check the info regarding the height of the highest/lowest point and the size of the square area, because you might have to adjust the size in Vue by entering the right values in the X Y Z size input fields for this terrain, otherwise it probably will look stretched or squished
Now just save the terrain in DEM format (or what else you need), because this DEM-file can be loaded directly into Vue using the 'Files - Import Objects' option.

The rest is adjusting - sharpening or whatever you want to do with it ...

Kilanor,

Fantastic, many many thanks for all that detailed informatiom. Off to give it a go

Many thanks

Just to make sure, your DEM file will look right in Vue ...

The info, that 3DEM gives -  look at the image i've included
img524.imageshack.us/img524/9592/3demls5.jpg

You can see the highest point in your terrain by calling up this color scale bar (to the left in the above image) - here in this area it's 4.19 km ( roughly 4190m, the exact values you get choosing 'Modify Scale' - where another window appears showing the colors regarding to the certain heights and the exact altitude range values). You need to adjust this in Vue lowest to hightest point in comparison with your ZERO water line (ground line for example), to get the terrain looking right in the Z-value.

What else you need to know is the X and Y length of your DEM terrain.
By displaying the 'DEM Specifications' window (in the menu with 'Show DEM Specs').
Here you'll get the Longitude and Latitude range.

The above image shows -110.961 to -110.385 longitude.
Subtract 110.385 from 110.961 and you get 0.576
Multiply 0.576 x 110 km (110km is roughly 1 degree of the circumference of the earth) and you'll get 63.36 km as length in X-value.
Same calculation for the Y-value.

These are the values you'll need to input in Vue terrain size. This might be way to large scaled to work with in Vue - so down scale it by dividing it with10 or 20 for example - so you'll get like 6.3 km or 630m terrain size - to large of an area in Vue will give you trouble with eco or whatever, since it has to cover an extreme large area with plants ...

Well, it works just great. Just one question, not sure how you work out the size and height from the Lat and Long co ordinates in the bottom right corner?

Sorry didnt see you post above

Kilnor

That answered my questions. Many Thanks

Also I think you have to change the terrain mapping to 'World Standard' to keep the dimensions correct as you resize

Here is an example - Mount Moran next to Jackson Lake - Grand Teton in Wyoming ...
The quick calculated scene above and a real photo from the internet (through Google Earth photo links) in comparison between virtual and real landscape:

img253.imageshack.us/img253/9484/mountmoranjacksonlakevutp1.jpg

I might have to adjust the height just a little better - but it does work very good in my opinion.

Yep, I had a DEM of 26KM *23KM in Vue and it would not populate with an eco system, to big for my machine, (1GB mem)

Kilnor, wow, great work.