36 replies to this topic

[JoeFred]

Can someone please provide me a source of TIFs of shaded relief (only) at 1:25,000 scale covering the Great Smoky Mountains National Park? I wish to use them for backgrounds for maps using Adobe Illustrator to create my own topo contours and other layers. I have the USGS 7.5' 1:25,000 topo map TIFs already.

JF

[SteveR]

Hi JoeFred,

Peter Guth's Microdem can make shaded reliefs. First you'll need a seamless DEM of your project area, getting it in GridFloat at probably 1/3 arcsecond resolution. The way you'd do it is to open the DEM and then one of your topo maps maps and set it at 1:1 scale. Right click and select Display Parameter, Blank. Now do a right click and select 3D Map Options. For shading, select Terrain Shadows. For Stereo Mode, select None. The result will be a map at the same scale as your quadrangle which only shows the shaded relief. It can serve as a base map to which anything else can be added. Here are some links:

Microdem:
http://www.usna.edu/...em/microdem.htm

Seamless USGS:
http://seamless.usgs.gov/index.php

[JoeFred]

Thanks, Steve.

I'm anxious to try my hand at that.

JF

[JoeFred]

I've installed Microdem and downloaded a zipped file of the seamless DEM of the project area.

Question: is there a particular directory in which I need to unzip the DEM files?

JoeFred

[Nick H]

Question: is there a particular directory in which I need to unzip the DEM files?

No, you can put them anywhere where you can find them again. You might have a look at 3DEM for rendering DEMs too, see a recent thread:

http://www.cartotalk...?showtopic=5273

Regards, N.

[JoeFred]

...
First you'll need a seamless DEM of your project area, getting it in GridFloat at probably 1/3 arcsecond resolution. The way you'd do it is to open the DEM and then one of your topo maps and set it at 1:1 scale. Right click and select Display Parameter, Blank. Now do a right click and select 3D Map Options. For shading, select Terrain Shadows. For Stereo Mode, select None. The result will be a map at the same scale as your quadrangle which only shows the shaded relief. It can serve as a base map to which anything else can be added.
...

This newbie is just about there... I think. I've gotten the DEM in GridFloat and opened it in Micodem.

Re. opening one of my topo maps.

• Is this referring to a raster file? (What I have is a 250 ppi TIF of the area comprised of merged portions of the USGS 7.5' quads involved.)
• How is the topo map opened?

JF
PS. Nick, I'll give 3DEM a look. Thanks.

[SteveR]

Hi JoeFred,

You're almost there. If your 250 lpi TIF is a geoTIFF, when you open it you should be able to see some coordinates and the elevation at the bottom of the screen as your mouse pointer wanders over the map. There will also be a dual cursor that points at corresponding features on the digital model. A geoTIFF has the map coordinates writtin into the image. If your map isn't a geoTIFF, you should find a tfw file with the same image name and select it when opening the map.

Most scanned topo maps (called Digital Raster Graphics, or DRGs) are aligned to the UTM grid, and if your map is in the wrong UTM zone the DRG won't drape to the DEM. One way you can check this is to open a vector map (on the map's toolbar) and point at something on your map, then see if the dual cursor on the world map is in the right location. If it isn't, you can edit and correct the DATUM file that Microdem created. Microdem's default setting is zone 11 (California); sometimes Microdem automatically assumes that's the zone where your DRG belongs, without asking.

Steve Richardson
www.2i3D.com

[JoeFred]

Steve, mine is not a geoTIIF and I'm not aware of any tfw files. Such doesn't appear to be among the files downloaded with the DEM. What is the source of geoTIFF files? tfw files?

JoeFred

[SteveR]

Dear JoeFred,

The DEM should already be internally registered. The TFW file might accompany the quadrangle map TIF image you have. I don't know where your quadrangle map image came from. Most GIS sources make world files of the same name available at the same site at which you get your image. If that's not true in your case, you can create a world file yourself. Look up registration in Microdem's help file. You need to determine if the map is aligned to geographic or UTM grid, and use the quadrangle's corners to register.

Another approach might be to just open your DEM, then <right click> on the mouse and select Load, TerraServer Maps. This will allow you to bring in a registered map of the area, and various controls allow you to shift and modify its coverage. When you've got what you want, select the Open Map button, and the view will become a real map, which you can use for your shaded relief project. Make it 1:1 and save it if you want to keep it.

Steve R.

[JoeFred]

Steve,

I now have an actual geoTIFF for the project area (mount_le_conte via http://www.tngis.org/drg_quad_sp/ ).
Using Microdem, I opened my DEM. Then I opened my geoTIFF, verified it is aligned to the UTM grid and using the vector map/dual cursor test, determined it is in the right zone.

How exactly I do set it at 1:1 scale?

JoeFred

[Nick H]

Steve,

I now have an actual geoTIFF for the project area (mount_le_conte via http://www.tngis.org/drg_quad_sp/ ).
Using Microdem, I opened my DEM. Then I opened my geoTIFF, verified it is aligned to the UTM grid and using the vector map/dual cursor test, determined it is in the right zone.

How exactly I do set it at 1:1 scale?

Microdem does that. Okay, you have your DEM open in one window and your raster open in another one. Right click on the raster, select 'Map Shading Options', click the 'Terrain Shading' button, then click OK. All from memory, but I think this is about right.

Regards,
Nick.

[SteveR]

JoeFred,

In the case of the map I opened from the source you provided, 1:1 means the map will be displayed at the scale of 8 meters per pixel. To get the map to that scale, there's a tool in the map window that looks like a magnifying glass with a "1" in it.

In addition to what Nick said, you should select click the boxes that specify Terrain Shading and Greyscale. If you still only want shaded relief without the map details, you would right click and select Display Parameter, Blank. Then you can proceed with building your map on the shaded relief base.

Steve

[JoeFred]

Thanks, Nick & Steve. I'll sure use that info, but for now... alas, I've gotten ahead of myself yet again

Here's the thing. As expected, the TVA-produced DRG did not include geoTIFF informtation, and I've yet to locate a corresponding TWF. Oddly enough the DRG downloaded file set did include the file mount_le_conte.twf, but it is only 1 KB. Opening it in Notepad yields
8.00
0.00
0.00
-8.00
2637158.3
478767.56
Can't be it, right? So... it appears I need to create a world map myself, after which I anticipate using Chuck Taylor's TVA DRG Repair Tool to add GeoTIFF information to the DRG.

Before that though, please expand on how to create a TWF. As suggested by Steve I looked up "registration" in Microdem's help file, but I need a bit more help. For starters, is the TWF created using just Microdem?

JoeFred

[graveldraw]

There used to be a GeoTiff Examine program available on the web. It writes out the twf from the infomation embedded in the .tiff file. If you can't find it, someone can find a copy for you. I have it somewhere...

Dan

[SteveR]

Dear JoeFred,

Ok, I downloaded one of the quadrangles (Alpine.zip) and opened it in Microdem. It's already a geoTIFF, so you don't need the TFW file that's already there among the zipped files. However the maps appear to be in US Survey feet rather than meters (8 feet per pixel), and though Microdem is able to open this type of image, it's complicated, but not impossible (in Microdem's Help, see "State Plane Coordinate System for Imagery").

The software Dan is referring to is probably GeoTIFF Examiner; I opened the image in that but it doesn't have provisions for making transformations to State Plane Coordinates.

Unless your objectives have changed, all you want is a georegistered blank image on which to make a shaded relief. I'd recommend right clicking on your DEM and selecting Load, TerraServer Maps, and proceed as described in my message of Feb 21 2010, 08:20 AM.

Steve