Georeffed data layers - how?

[radhock]

I've trawled thru a lot of the forums on how to do add-ons, and find no intuitive problem in processing Arc data despite my lack of French (looks like it would sort out WW Acid neatly), but I still lack an idiot's guide for how to process a bunch of geofrefrenced tiff data (or georeferenced jpeg tiles) from a giant file down to a stack of tiles that load like the NLT etc data. Am I missing something? I've looked at dnither's guide and Chris Maxwell's explanation of his processing system for NLT Landsat, but it doesn't seem to give the idiot's system for generating tiles. The file-naming system, yes. The overall process, yes. But not a step by step guide for getting public georeferenced data to display in the same fashion as NLT or Community Landsat, with SRTM data overlayed/working with it as in the normal Landsat views.

At stake: processed SRTM image data of Australia (WA for a start) as at http://jaeger.earthsci.unimelb.edu.au/Imag...m/landform.html, geology of Western Australia, geophysical data for much of WA, and topography like USGS topo for WA, as delivered by GSWA via web but not WW as yet. It's a private hobbyhorse almost, to get great data happening.

What is needed is a guide for those who don't hit the chat room, with necessary downloads provided, to make it easy for those who may have given up coding 15 years ago. Is this possible? I haven't found it yet in the forums.

[crcorp]

Well, you're definitely not the only one. What I do know is how to make tiles from a large file to those who are fitted for use in World Wind. My problem is that I have a dataset (one giant BMP file of 1.8 GB) which obviously must be transformed in one way or the other to get it into the same projection type as World Wind uses. When I'm right this process is called georeferencing.
So if your file(s) are already georeferenced, the trick is quite simple (if you know the exact latitude and longitude coordinates of your image). You can use the functions here below to get the necessary information about how to convert between tilenumbers and latitude/longitude coordinates:

(code is VB6)

Private Function GetXFromLongitude(level As Integer, longitude As Double) As Integer
  Dim tileSize As Double
  
  tileSize = LevelZeroTileSizeDegrees / (2 ^ level)
  GetXFromLongitude = Round((Abs(180 + longitude) Mod 360) / tileSize, 2)
End Function

Private Function GetYFromLatitude(level As Integer, latitude As Double) As Integer
  Dim tileSize As Double

  tileSize = LevelZeroTileSizeDegrees / (2 ^ level)
  GetYFromLatitude = Round((Abs(90 + latitude) Mod 180) / tileSize)
End Function

The code is quite self-explaining I think. What rests is to make a division of the large image into tiles of 512x512 pixels each, store them in the right directories. Perhaps for your case, this helps...

[radhock]

Thanks for the advice, but I think the key issue remains. For someone who has georeferenced data (this assumes the georeferencing is correct and accurate) that is available free of copyright etc, a step-by-step guide as to how get it ready to serve it in Worldwind (WMS servers etc - not my issue) is desirable. Basically:
<have data - giant geotiff file>
<split to tiles>
<split further to smaller tiles?>
<convert to WW filr name system>
<serve the tiles>

I'm still missing a stage or two, despite the code fragments. Somone feeling generous?

[Neimo]

I'm not a programmer, aside a from a semester in C++. I can run stuff from a command line, but I don't know how to compile and run the various scripts. I'm sure quite a few people who would like to add layers are in the same or less-knowledgable situation. This being a windows-only program, users shouldn't have to compile for their flavor of linux. When there's a set of self-contained tools with step-by-step instructions, I'm sure there will be an increase in content available.

[crcorp]

Yup... I'm trying to put a dataset I downloaded (a big 1,8 GB BMP file) into World Wind for my homecountry (The Netherlands). I am a programmer, but it seems that some people from NASA don't want to help you (much) when they have doubts about the 'legality' of the material you're using. Under Dutch laws everything I do is perfectly legal, so nobody needs to worry.

Nevertheless from the 8 characters (yes it is much ) I got as 'help' (these were "gdalwarp") I've been able to retrieve some interesting information. Perhaps this could be helpfull to you too:

First of all, an interesting toolkit for transforming and georeferencing some stuff is this Windows executable: FW Tools (windows version). When installed, you find in the program's subdirectory 'bin' some interesting tools, as well as this famous "gdalwarp".

Not every GeoTiff (or other image format like JPG, BMP, GIF, etc) has the right projection to use it in World Wind. This gdalwarp tool can assist you in transforming the image into a new one for a different projection. A little interesting tutorial on this issue can be read here: MSH Tools.
Executing the procedure written on this site, I found out that parameters for the georeferencing in case you use a JPG file is stored in a separate JGW file. How this JGW file is built up and how to adapt it manually, see here.
If you want to use UTM, this might be helpfull as well.

Then for your key-issues radhock, perhaps this might help:
Splitting a giant GeoTiff file into tiles is quite a simple task, if you have a nice programming environment... until now I haven't been able to find any free tools on the internet that perform this tiling automatically for you, so that's why I wrote a very simple program for doing so. The idea is to convert the GeoTiff file to a BMP file and load it into an image-component in Borland Delphi. Into a second image component you load piecewise the tiles of 512x512 pixels and save that tile each time. How to perform the World-Wind numbers on them you can find in my previous post.

Summarizing, I fear that what you want to do is something that (at this stage) still requires quite some programming experience. Even for me it's a hard job. But I'll keep in mind the idea that when I succeed in my mission to create a program that does all these jobs automatically...
Of course I'll make that program available when I succeed in doing so...

[radhock]

Thanks. This may take a while to digest, but as long I'm getting one and a half steps forward for each step back, I'll be happy. The data isn't an issue - it is public domain (currently served on the web anyway, but by a different method without SRTM overlay), and part is with NASA at present, but they're busy enough as it is. Neither is projection - I'm surrounded by GIS gurus in an Arc and ER Mapper environment - but I'm just the dumb geologist with an interest in progressing our data rather than relying on someone else to do it. Let you know how it goes....

[crcorp]

OK and good luck
If I can be of any help, please don't hesitate to post here or to send me an e-mail (for the address, you can look on my website in my profile).

Hi, crcorp, can we have news about your program ?

[JamesCanada]

Global Mapper will make tiles from GeoTiffs or other files very easy. The fun part is renaming the tiles to match WW. Global Mapper counts from the top left, WW counts from the lower left.

[5of0]

Originally posted by JamesCanada@Jan 8 2006, 04:57 PM
Global Mapper will make tiles from GeoTiffs or other files very easy. The fun part is renaming the tiles to match WW. Global Mapper counts from the top left, WW counts from the lower left.

Quoted post

It wouldn't be too difficult to write a script to do that, though. No promises on this end, however.