USGS & "Earth Explorer" for TG2

[cyphyr]

Hi Jo
Yes, of course you're right. I just re-ran my test with the same file. It worked fine however the tif had to be run through Global Mapper to generate the tfw file as this wasn't included in the download from the USGS site.
As I mentioned earlier:

"I had to take it through Global mapper because the Terragen says on loading "Please convert to SGI for non standard Bit depths". Maybe I'm loosing some meta data in the conversion although GM still loads both old and new files at the same size."

The geo-referencing data must be within the geotiff file somewhere, in the header I assume, but it's odd that my exported geotiff is nearly twice the size of the original but lacks this geo-referencing data which has to be supplied via a separate file. (It's twice the size as the file has been converted from 16bit to 32 bit in GM).

It would certainly be helpful if TG could read "non standard Bit depths" without having to convert the file via another program especially since GM is relatively expensive and the SGI plugin for Photoshop is not readily available (well I haven't been able to find it or when I have, get it to work).

Richard

[TheBadger]

Hmmmmm

When I downloaded from http://viewer.nationalmap.gov/viewer/ my resulting .tiff opened in Photoshop at 32bit. The file I got from the other source was opened at 16bit.
But I must convert to 8bit.
1) What if any value was there to the file being 32bit in the first place (from a TG2 perspective)?
2) Does 32bit help to preserve detail against loss when adjusting levels and exposure in PS, again from a TG2 perspective?
3) Does it matter if I convert "mode" before or after making adjustments? Normally I would say yes! But with this stuff, I have no idea.
4) Should I treat the data in photoshop just like a photo?.. I have to say, It does not feel like I should.
5) Please someone clarify. I should always have a .tfw file in my data download, or I must always/sometimes make one?


On a related subject. There was a video posted in image sharing a few months (or so) ago. Where the video was made entirely from satellite data. I remember that it included a view of a construction site that would have been a long nightmare to do manually/procedurally. Does anyone recall this video? It was posted by someone who does not post often, it may have been his first post?
In the light of this thread, I really want to see that video again. But I cant find it. Hope someone reading this can remember it?!!

[rcallicotte]

That's crazy.  Both IE and Firefox state that the viewer.nationalmap.gov server does not exist.  Did you guys install something in order to see this site?

[cyphyr]

Hmm I cant get the viewer page to load properly either. It just says loading just below a quick tip box.

Badger, why do you want to convert to 8 bit? You'll end up with only 256 levels of grey and get very obvious "stepping" in your terrain. Although you will end up with an easily editable image you'll loose the fine resolution. As I mentioned above be very careful using Photoshop to edit GeoTiffs, they are NOT to be treated as a photo/image, the height data is only "represented" by greyscale values.

Richard

[TheBadger]

"Please convert to SGI for non standard Bit depths"

Did I misunderstand this?

[bigben]

Hmmmmm

When I downloaded from http://viewer.nationalmap.gov/viewer/ my resulting .tiff opened in Photoshop at 32bit. The file I got from the other source was opened at 16bit.
But I must convert to 8bit.

I wouldn't do anything with it in Photoshop if you're using it as a terrain file. It's just elevation data wrapped up in an image format.

On a related note, I still prefer to export as TER mainly because I change the projection from geographic to UTM

[TheBadger]

I wouldn't do anything with it in Photoshop if you're using it as a terrain file. It's just elevation data wrapped up in an image format.

HI Ben, thanks.
But you confused me on this again. If I cant use photoshop, or shouldn't. How do I manage the file? Or does this ".tfw" file control the data, so that I don't need to do anything to the file unless I want to distort it?

After being informed of this file extension .tfw I looked and sure enough it came down with the .tiff. So I just need the two files and the rest I can trash? Or do I need to keep all of the files that come in the downloads in a library?

[bigben]

The tfw file is just a text file. Open it in a text editor and you'll see that it defines the boundaries of the data. A proper geotiff file should still import OK into TG without a tfw, it's just that TG won't know how big/where to make the terrain.... and extrapolating from that, if you know the correct values to put in, you could create the tfw yourself.

[billg60]

It has been a while since this thread was active but it started out right on topic with my question. I am using the relatively new http://viewer.nationalmap.gov/viewer/ as my source of DEM. The problem is that the GeoTIFF file does not end up containing a .tif file. I have tried the only two sub-formats I have seen provided: ArcGrid or float and neither results in .tif file in the zip. Any help would be appreciated.

[Oshyan]

There's a note on the USGS site that reads as follows:

Note: As part of the National Geospatial Program's geospatial data delivery plan for delivering data from a public internet cloud provider by the end of 2013, The National Map is preparing prepackaged, staged products for faster and more efficient downloads. Beginning December 18, 2012, NED 1- and 1/3-arc-second data will be available through prepackaged, downloadable, 1- degree tiles in ArcGrid and GridFloat formats only. Users can still define custom areas of interest. However, all tiles intersecting the area of interest will be included in the delivery.

In addition, beginning with the April 2013 release of the NED, it is anticipated that all elevation products (1-, 1/3- and 1/9-arc-second DEMs) will be available as prepackaged, downloadable files in .img format, a robust format easily read by nearly all GIS software. Due to 1/9 arc-second data's very large size, it will only be available as prepackaged data in '.img' format through online download starting with the April NED release. And while USGS continues to offer ArcGrid and GridFloat formats through our bulk order process, all other format options for on-line download of 1/9 arc-second DEMS will no longer be available after the move to staged products is completed.

We are considering offering a second prepackaged format for 1/9 arc-second data if budgets allow. We will be posting more information about the change to prepackaged products soon. If you have questions or concerns about these changes, please contact us at tnm_help@usgs.gov.

So unfortunately it looks like much of the data is no longer available in GeoTIFF. Terragen will support more DEM formats in the future. In the meantime you'd have to convert, but there are some free tools available that can do this (e.g. Landserf).

- Oshyan

[lat 64]

Rats!

Well Oshyan, please don't drop support for tiff import. I like to create my own in Photoshop for carving rivers into DEM tiffs. Sortof like Terragen classic. I have to work in a very narrow band of shades when I "carve" the land by using a brush tool.

1 pixel = 1 meter This I did not know, very useful info. Thanks.

I'm having some dialog with a friend at the University of Alaska about lidar data and he says he can probably help me with getting high resolution DEMs as tifs that I can play around with. Things are changing at his shop too. I'll try to make sense of it and share any good news.

Russ

[Oshyan]

We won't be dropping support for any formats, just adding more.

- Oshyan

[billg60]

The USGS has updated the site now to include a link to scripts that will facilitate conversion to the legacy formats including GeoTiff.
>>>
In addition, beginning with the April 2013 release of the NED, it is anticipated that all elevation products (1-, 1/3- and 1/9-arc-second DEMs) will be available as prepackaged, downloadable files in '.img' format, a robust format easily read by nearly all GIS software. Due to 1/9 arc-second data's very large size, it will only be available as prepackaged data in '.img' format through online download starting with the April NED release. And while USGS continues to offer ArcGrid and GridFloat formats through our bulk order process, all other format options for on-line download of 1/9 arc-second DEMS will no longer be available after the move to staged products is completed. To assist users in this transition to our new product format offerings, we are also providing downloadable file conversion scripts to assist users that need the data in other formats.
>>>
The link is http://imsdemo.cr.usgs.gov/Website/Ned_Conversion_Scripts.zip and uses the GDAL tools from http://www.gdal.org/ which are open source.