Question about Min and Max values of height map

I am using a real world island that is a little larger than Altis at 315 km2.

I am using grid size 2048X2048 with a cell size of 5m. I believe Altis uses a 4096X4096 grid with a 7.5 cell size.

Altis's Min & Max values for heightmap are {-231,350}, while my values are {-5,1634}.

My question is, are those values based on a 1m cell size? Should I divide the values by 5 since my cell size is 5 giving a more realistic height result? Because at 1634m

my mountains are way too high to be realistic. The whole terrain is very hilly. Is 2048 too small causing the terrain to sort of "scrunch up" in size and push everything skyward?

Would I be better off stretching out to a 4096 and increasing my cell size to reduce the mountains?

I hope I am asking this correctly and not confusing you.

I can't quite wrap my head around your question, maybe I need more coffee.

You say your island is slightly larger than Altis but:

2048x2048x5 gives you 10km2 while Altis is 20km2 I think?

I'd think the min - max values are just based on the highest and lowest point in your heightfield.

Is there any way I could persuade you to post a screenshot of the mountains? :3

They sound interesting.

All that rambling actually brings me to a question:

What size was the original heightfield data? If you've resized it from 4096x4096x5 to 2048x2048 without changing the horizontal 5 meters to 10 meters, you would end up with very high mountains.

I can't quite wrap my head around your question, maybe I need more coffee.

Let me try to explain this better :)

You say your island is slightly larger than Altis but:

2048x2048x5 gives you 10km2 while Altis is 20km2 I think?

The overall size of my world is 325km2, Altis is 275km2.

Think of it like this, Altis' 275km2 world sits inside a box that is 4096x4096 with 7.5 cell size for a total of 30km2

I want to keep my world a little smaller, so I am trying to fit 325km2 inside a box that is 2048x2048 with a 5 cell size for a total of 10km2. What I am wondering is, since

my world is larger and I am trying to fit it in a smaller box am I forcing the contents of my world upward causing higher peaks?

Is there any way I could persuade you to post a screenshot of the mountains? :3

They sound interesting.

Yea, I will post one shortly

What size was the original heightfield data? If you've resized it from 4096x4096x5 to 2048x2048 without changing the horizontal 5 meters to 10 meters, you would end up with very high mountains.

It was 2048x2048 5 when I imported it in L3DT

The more I think about this the sillier the question seems. Am I missing the boat on how the islands are sized grid wise and cell wise?

If I want to use real world data, how can I get the island correctly porpotioned in size and scale?

LOL, this is one confusing thread. I hope I'm gonna clear it up with this question:

Are you shrinking down your island?

If so, yes, you do need to adjust the vertical range. Your mountain is probably looking like a stalagmite?

Perhaps I can clear this up if I explain the steps I take to get to the TB phase.

1) I choose my real world data and download a zip file containing all the tiles of my island.

2) I drag the zip file into Global Mapper. I change projection of my island to UTM. I choose the digitizer tool and draw a square around the entire island. I

then export a DEM file changing the x and y axis sample spacing to 5 and 5 {I am assuming this is the cell size I need?} and choosing the crop feature of the export bounds.

{{{{Is this the step I am messing up on? Should I even change the sample space? It starts out at x=24 and y=30}}}}

3) I take the DEM file and open it up in Microdem. Right click, choose display parameter, elevation, then tick gray scale. Right click again and save as bmp. Also choose map info to jot down elevation values.

4) Open bmp in Photoshop resize to 2048x2048. Convert to grayscale save as 8bit bmp.

5) Import bmp into L3dt giving cell size 5 and changing terrain min and max to correct values. Generate heightmap, mask, sat. Export as ASC and bmp's.

6) Paint mask and sat in photoshop, resize and export as bmp.

7) We are at the Terrain Builder phase now.

I have absolutely zero experience with both Global Mapper and Microdem I'm afraid but I know some of the other people here do use those so they can probably provide useful input. An image of the result in Buldozer would be useful too. I'm off to bed though :)

I have absolutely zero experience with both Global Mapper and Microdem I'm afraid but I know some of the other people here do use those so they can probably provide useful input. An image of the result in Buldozer would be useful too. I'm off to bed though :)

http://s23.postimg.org/duu30v48b/image.png (169 kB)

Perhaps I can clear this up if I explain the steps I take to get to the TB phase.

1) I choose my real world data and download a zip file containing all the tiles of my island.

2) I drag the zip file into Global Mapper. I change projection of my island to UTM. I choose the digitizer tool and draw a square around the entire island. I

then export a DEM file changing the x and y axis sample spacing to 5 and 5 {I am assuming this is the cell size I need?} and choosing the crop feature of the export bounds.

{{{{Is this the step I am messing up on? Should I even change the sample space? It starts out at x=24 and y=30}}}}

Set your UTM before you drag the stuff in. Don't change the spacing here. Globalmapper does a bad job of resampling. Resample in L3DT instead.

3) I take the DEM file and open it up in Microdem. Right click, choose display parameter, elevation, then tick gray scale. Right click again and save as bmp. Also choose map info to jot down elevation values.

4) Open bmp in Photoshop resize to 2048x2048. Convert to grayscale save as 8bit bmp.

Why are you putting into Microdem and Photoshop? You should be able to go from Global Mapper straight to L3DT using any number of formats. I normally use ASC.

Set your UTM before you drag the stuff in. Don't change the spacing here. Globalmapper does a bad job of resampling. Resample in L3DT instead.

Ok, will try that.

Why are you putting into Microdem and Photoshop? You should be able to go from Global Mapper straight to L3DT using any number of formats. I normally use ASC.

I followed some tutorial.

Thanks Jakerod.

For what it's worth - those mountains don't look too strange to my eye. If it's a real location, maybe eyeball your elevation against the same view in Google Earth?

http://s23.postimg.org/duu30v48b/image.png (169 kB)

I agree with Major_Desync, I don't see anything odd about it. I quite like the look of that terrain actually.

I took the height map and took a photo at each of the following values always from the same position to accentuate the differences in terrain height.

2048 with cell sizes 5,10,25

4096 with cell sizes 5,10,25

8192 with cell sizes 5,10,25

The min and max height values used are real world -5 1626

As you can see, 2048/5 is way too mountainous as is 2048/10. While 2048/25 is perfect except the map would be over 51km2.

4096/5 is also too hilly, while 4096/10 is good but over 41km2, and 4096/25 flattens out too much and is over 102km2.

Now 8192/5 is a little hilly and 8192/10 is perfect but again too large at 81km2. 8192/25 is a vast flat land at 204km2.

Any thought on which one you would go with? I guess I could fudge with the max height value and reduce the moutain that way, but I was trying for authenticity.

I want to keep my world a little smaller, so I am trying to fit 325km2 inside a box that is 2048x2048 with a 5 cell size for a total of 10km2. What I am wondering is, since

my world is larger and I am trying to fit it in a smaller box am I forcing the contents of my world upward causing higher peaks?

Yes - you're basically "scaling" the X and Y distances, but not the Z (height)...

Am I missing the boat on how the islands are sized grid wise and cell wise?

Sortof... a bit... yes...

If I want to use real world data, how can I get the island correctly porpotioned in size and scale?

You have to make it the size it is... If a place is too big, either you pick another place, or you Scale (down)...

Scaling has it's issues and rarely works well... I tried it once - with my very first island... :( (of course)...

I decided I'd make a 200km x 200km chunk of Scotland - in a 20km x 20km size...

It was a bad idea....

eg: - a runway which on the realworld map was 1km long became an unusable 100m long - the only alternative was to have a "toytown" runway no plane could use, or make it a "proper size" - unfortunately, making it 1km long meant it entirely covered the little "town" next to the runway.

Towns which were 2km wide became villages 200m wide, houses would have to be the size of dog kennels - worse still - hugely impressive mountains with peaks over 1000m became 100m small hills (I scaled heights too - to keep things "in proportion").

That's an extreme example, but the concept is the same - scaling is dodgy at best and rarely works well...

Think of it like this, Altis' 275km2 world sits inside a box that is 4096x4096 with 7.5 cell size for a total of 30km2

Because that's the size the "Real Altis" is, and thats the size of "box" it will fit into...

Lets try an example....

• You've spotted a nice little realworld island.... it's almost exactly 12km wide at its longest/widest point...
  
• To make this in a realworld size, we need to figure out what grid & cell sizes to use
  
• We're stuck with preset grid sizes - 1024x1024, 2048x2048, 4096x4096 - but we can vary cell size
  

(though its best to try and stick to relatively "sensible" and easily divisible cell sizes, so - 7.5meters per cell = ok... maybe, whereas 7.14265meters per cell = Definite Bad Idea)

so... the target is 12km wide - maybe allow for a little "sea" all around... lets guess at about 14-15km as a suitable "terrain width/height"....

2048 cells @ 10 meters per cell = 20480 meters width = too big

1024 cells @ 10 meters per cell = 10240 meters (10km) = too small

2048 cells @ 7 meters per cell = 14336 meters (14.3km) = Good!

2048 cells @7.5 meters per cell = 15360 meters (15.3km) = Also Good!

Since the actual realworld island is only 12km wide, I'd probably settle for the 2048x2048@7m size (14336 meters).

So now - all you need is a heightmap of that realworld island - a heightmap which is 14336 meters wide.

Lets see how you've been getting your realworld heightmaps....

1) I choose my real world data and download a zip file containing all the tiles of my island.

Sounds good - you grab the best and cleanest data you can find, the highest res you can get...

2) I drag the zip file into Global Mapper. I change projection of my island to UTM. I choose the digitizer tool and draw a square around the entire island.

Jakerod has already mentioned setting your Projection FIRST - before you load the data - that basically tells GM "This project is in UTM Zone <whatever>, WGS84", so any data you subsequently load will automatically be reprojected to the "project coordinate system" - which is the correct UTM, etc (and all measurements will now be happening in Meters, which will come in handy just shortly...

I choose the digitizer tool and draw a square around the entire island.

Almost there....

Once you have the Digitiser tool active - Right Click on the area and choose the "Create Area/Polygon Features > Create Rectangular/Square Area (Specify Coordinates)" option.

In the dialog box which appears, choose the "Corner w/size - Global Projection" option

(since the Global Projection is already set to UTM, all measurements are in meters so - look at the required parameters for this Box Drawing Option)...

There's "slots" for "North" and "West" - obviously these are for the X,Y coordinates of the corner of the box. And theres slots for "Width" and "Height" too...

The North & West boxes will have values already - they'll be the coordinates of the point where you right-clicked - ignore them for now...

The Width and Height slots will have values too - BUT - we know what Width and Height we want - we worked it out earlier, remember?

So - for our example, you'd type "14336" for each of these values - then hit OK.

Now you have a "Cropbox" which is exactly 14336 x 14336 Realworld Meters in size

(It'll be out of position, but you can right click on it with the digitiser tool and choose "MOVE" and drag it until it neatly frames your target island on the overall heightmap data you loaded)...

Now you can export just that 14336 meter "chunk".

then export a DEM file changing the x and y axis sample spacing to 5 and 5 {I am assuming this is the cell size I need?} and choosing the crop feature of the export bounds.

This is the procedure, except - DON'T change the X and Y sample settings!!! - Leave them at whatever crazy values they happen to be. Just export the heightmap as an Arc ASCII .asc grid file, using the box as a "cropbox" to define the output bounds.

Of course - your actual heightmap data wasn't conveniently using a 7 meter cell size - maybe it was actually 70 meters, so instead of a 2048 heightmap file, you might end up with a 204 - THAT DOESN'T MATTER!

It's 14336 meters wide - that's all that matters.

Now you need to get rid of the built-in projection, since we have to force all data to that pesky TerrainBuilder "preferred location", so...

If there was a *.prj" file generated alongside your main heightmap file - delete it!

Then - import the heightmap into L3DT - then immediately - without doing ANYTHING ELSE - choose to export it again, as an .asc file - again...

As you do so - notice that theres an "options" button at the export stage in L3DT - click that...

Change the "UseProjGeoref (bool) value to "false"

Export the heightmap file...

Now you're ready to import into TerrainBuilder...

Once the file is loaded into TB - right click it on the Raster images list, and choose "Terrain Coordinates & Properties"

Set the Easting & Northing to TB's "preferred location) of 200000E, 0N

and...

Set the Width and Height to...... you guessed it - 14336 meters - 'cause that's what it is!

Now - in your mapframe Location tab - make sure the Mapframe is using the same Bottom Left coordinates of 200000E, 0N

Then - in the Sampler Tab - Top Left Terrain section...

You guessed it again...

You set 2048x2048 grid size, and 7 meters cell size - TB will report that this is going to result in a terrain which is 14336 meters wide...

(At this point, take a moment to realise that a 4096x4096 grid with 3.5 meter cells, or a 1024x1024 grid with 14 meter cells would result in the exact same size of terrain - all three are potential viable settings, though I think we've chosen the best all-round values already)

Go to the Processing Tab and hit "Rebuild Terrain", then hit "OK" to leave the Mapframe Properties and...

You're done

You have a realworld heightmap - of the exact physical realworld correct size, in the grid and cell size you want - forced into the location that TB demands...

(Notice how, after the initial planning/concept stage, we didn't even consider grid or cell size until we got to the end and the TB stage - in between we were working entirely with meters)

All of this stuff - explained in a bit more detail, and possibly even with an illustration or two, will - eventually - be one of the little "mini tutorials" that I'm currently working on, but in the meantime - this brief rundown should get you started...

Good Luck!

B

Because that's the size the "Real Altis" is, and thats the size of "box" it will fit into...

Lets try an example....

You've spotted a nice little realworld island.... it's almost exactly 12km wide at its longest/widest point...

To make this in a realworld size, we need to figure out what grid & cell sizes to use

We're stuck with preset grid sizes - 1024x1024, 2048x2048, 4096x4096 - but we can vary cell size

(though its best to try and stick to relatively "sensible" and easily divisible cell sizes, so - 7.5meters per cell = ok... maybe, whereas 7.14265meters per cell = Definite Bad Idea)

so... the target is 12km wide - maybe allow for a little "sea" all around... lets guess at about 14-15km as a suitable "terrain width/height"....

2048 cells @ 10 meters per cell = 20480 meters width = too big

1024 cells @ 10 meters per cell = 10240 meters (10km) = too small

2048 cells @ 7 meters per cell = 14336 meters (14.3km) = Good!

2048 cells @7.5 meters per cell = 15360 meters (15.3km) = Also Good!

Since the actual realworld island is only 12km wide, I'd probably settle for the 2048x2048@7m size (14336 meters).

So now - all you need is a heightmap of that realworld island - a heightmap which is 14336 meters wide.

Well after reading your novel :P, I believe I finally understand how this works.

My Island is 45km with a little sea around it, so I would have to make my cells sizes at:

1024 cells @ 44 meters per cell = 45056 meters (45km)

2048 cells @ 22 meters per cell = 45056 meters (45km)

4096 cells @ 11 meters per cell = 45056 meters (45km)

8192 cells @ 5.5 meters per cell = 45056 meters (45km)

This Island, I'm afraid, is a little too big for a first build project. So back to the Atlas.

All kidding aside, thank you ALL for the invaluable help you provide to those of us who try to learn this stuff. It really means alot that you guys

take the time to provide answers to all of these questions we have.

I also look forward to your completed novel.....wink wink......mini tutorials. lol

Ignore this

I have run into a problem at this step. When I start GM and set projection to UTM, the bottom right corner tells me that my coordinate is out of range.

You start GM...

Go to "Configure"

Set a UTM projection

Click OK to go back to main view

... and

the bottom right corner tells me that my coordinate is out of range.

Are you absolutely sure that's what happens??

If there's no data loaded I can't see how a coordinate could be out of range....

B

Hey Bushlurker, What I was doing was setting the UTM to -60 instead of 34,

now have it sorted. thanks!