10 meter DEM quetion

[cirkut5732]

Hey everyone
Im not really new to the OFP editing scene but I am extremely new to DEM files.
I have been making a map via wilbur and wrptool and even with blurring I cant get the ground quite as smooth as say Nogova, (ground is a little choppy)
So I figured Id try out a DEM file So here is my problem

I downloaded 2 10 meter DEM files for the area of seattle, WA one N. seattle one S. Seattle and here is what I do
Open MicroDem v. 8.0 and merege the 2 DEM files, then save as a DEM.


Problem 1 = After merging and saving I try to Load the merged dem into 3dem and get the error "Not a DEM file" So I did something wrong there

Problem 2 = I read somewhere about opening Microdem and clicking the IN\OUT button then go to resample, DEM, and then Real DEM, When I go to resample I do not have these options

Problem 3 = I loaded N.Seattle dem file (not merged) Straight into 3dem, it loads, I save as a terragen file, Load it into Wilbur and save as a .txt LON file, I load this into wrptool and the island is all mangled, and not shaped correctly. So my big question is this

How do I take 2 dem files, Merge them, and get them to make a 512x512 map in wrptool?

Thanks guys!

[Planck]

10 meter DEM's are not what you want unless you can resample them to 50 metres.

If you can get 30 metre DEM's it would be a little easier.

To make a standard size of island in OFP you need to have a DEM that covers 12.8 X 12.8 km.
Usually getting dems of the area surrounding your area of interest and merging them will give you a larger area than you need.

Once you have the larger DEM you can decide which part of it you want to use and then cut the exact size from the original DEM.

Problem 1:

Indeed your DEM is no longer a USGS DEM it is an MDEM......MicroDem DEM.
If you need it to be a USGS DEM then you need to find a converter, such as MDEM2DEM to do the job.

Problem 2:

The latest version of Microdem has the resample option in a different location.

File Menu....Save DEM....Reinterpolate.

Problem 3:

It probably didn't work because the dem you used was not big enough to civer even the standard 12.8 X 12.8 km.



You need to get 30 metre DEMs
Whatever area you are interested in, you will be better to collect also the 8 surrounding DEMs, making 9 DEMs in total, which you then merge together.
Now you can Resample your merged DEMs to 50m.

You then need to Subset your merged DEM, choosing an area centred on your area of interest.
The resulting DEM must then be 25.6 X 25.6 km in size.


Planck

[cirkut5732]

I was hoping you would reply PLank, Your tutorial has been a great help so far!

So About the 9 dem thing, Are you saying If I merge 9 10meter Dems I will have the correct size dem file?

So take 9 10 meter dems, merge and resample the merged file to 50meter dem
then use mdem4ter to make a terragen file

Sorry if this sounds confusing but I really want to do the puget sound area (my home) Thanks again plank! By the way do you work for BIS! lol!

[Planck]

No.......Get 30 metre DEMs instead.

Merge them and you will have a BIG DEM, not necessarily the size you want.

You need to Subset the exact area you want from your merged DEM (In your case an area of 25.6 X 25.6 km) .....you will then end up with the size of DEm you want.

Guessing that you want North and South Seattle central to your area, the 9 DEMs you require only come to about 760KB in total.

I know because I have them.   ;D

You should read Grens tutorial from here

EDIT:  Presumbly the area you want corresponds to the attached picture.......maybe.


Planck

[cirkut5732]

Thanks again Plank I will try when I get home from work! And probably post again

[cirkut5732]

Im having a bit of trouble finding 30 meter dem files. does USGS website have them? ccause all files  I download from there are in .dat format, instead of .dem


Will these work?
http://duff.geology.washington.edu/data/raster/thirtymeter/wabil30/

They say there 30 meter dems converted from 10 meter ones, they download as .bil files

[Planck]

Yes.....USGS is the place to go.

Do you have a user account there.....I think you need one.

Anyway .......... Look Here

Alternately I can send you the lon/lat text file.


Planck

[cirkut5732]

with the Lon lat file can I can go straight into wrptool correct? and if so as 512x512


EDIT--- I signed up to that geocomm, So i need to download 9 of the 30 meter dems correct, so far Ive downloaded seattle north and south

other than that it looks like Ill be able to do this, Thanks so much plank!

[Planck]

Yes.......it is all ready for WrpTool.

I understand though that you may want to do it all yourself........it's the best way to learn.   ;D

If you want the text file, give me your current email address and I'll send it along.


Planck

[cirkut5732]

ya im gonna give it a shot, If i start pulling my hair out Ill send you my e-mail, thanks again Plank!!

[Planck]

so far Ive downloaded seattle north and south

The dems you probably want are:

Code: [Select]

Bothell      47122g2
Duwamish Head   47122e4
Edmonds East   47122g3
Edmonds West   47122g4

Kirkland   47122f2
This one needs a bit of tweaking as it is faulty.

Mercer Island   47122e2
This one needs a bit of tweaking as it is faulty.

Seattle North   47122f3
Seattle South   47122e3
Shilshole Bay   47122f4


Planck

[cirkut5732]

Ok, Im really close now!

I can take a dem and make a 256 map and get it to load into wrptool but not a 512 one

here are the steps I am taking to try to make a 512 map (same steps as 256 almost)

1.merge and subset my dem. Ok my NW corner is x=528900 and y=5265800 and I know you add 12800 to the x and subtract it from the y for a 256 map so I added 25600 to the x and subtracted that for the y to make a 512 map right?.....

2.Resampled the subset version of the dem. took height measurments, min= -6 , max= 1561 ( i know shouldnt be this high), changed columns and rows to 512, x and y spacing to 50, and tried both decimeters and meters for the Z unit. Saved the resampled dem

3.Loaded the resampled dem into wilbur, lowered the terrain around the perimeter to create an island, saved as LON .txt file with these options, widht and height to 512, max X and Y to 511, and then put in my heights, -6 and 1561, save and exit

4. load it into wrptool, select new, create 512 world, and load wilbur file, it loads and is strectched out. Ive made two 256 maps tonight with no problems, but the dem im using requires me to use a 512 version to get the whole island in there

What am I doing wrong
Thanks
CirKuT

Also some of my 256 maps are coming out with really point and high elevations when loaded into wrptool?

[Planck]

OK,

Merging your 9 dems together......you seem to have got that ok.
You have the Subsetting sussed as well plus 25600 for x axis and minus 25600 for the y axis.

The 2 dems I mentioned as faulty.......they both need to have all z values lowered by 4 metres.

Resampling........You need to change Cols: and Rows: to 512 each.
XY Units and Spacing needs to be 'Meters' and X=50, Y=50
Z Units also should read 'Meters', but don't bother changing the minimum and maximum heights......I think it detects those itself anyway.

Once you have Resampled, go back to Resampling again so that you can read the modified minimum and maximum heights which will now be in meters.
Take a note of them somewhere.
I think I got 0 and 194.

Once you get this into Wilbur you are correct about saving as a lon/lat text file.

However, once you have chosen a name for the file and the file type (lon/lat text), a requester pops up as you know......You must press the 'Set to Pixel' button first.
Now you can make sure all the other values are correct.

For minimum and maximum heights I put in -5 and 194

Your maximum height of 1561 cannot be right and might be decimeters...not meters.


Planck

[cirkut5732]

K plank....Just woke up after a 16 hour session with this yesterdsay, Gonna try it again now that I am replenished, By the way I changed my dem a little bit, Im using vashon Island now, just a little left of our current dem (that is why i need 512 map, it wont fit into a 256 subset.)

[Planck]

Yes......I know.

I did another one myself using the co-ordinates you stated in a previous post:

NW Corner
x=528900
y=5265800

SE Corner
x=554500
y=5240200

Of course this needed extra dems.  


Planck