Ready to start Solomon Islands theatre

This week I am ready to start moving things into CFS3. My main goal is to get things working using as much of the original CFS3 installation as possible. Later on I can experiment with higher resolution data. However the CFS3 scenery system is difficult enough as it is without trying to improve things from the outset.

The region I am working on is centered at S7.5 , E152.5 and is planned to cover a similar area to CFS3 Europe.

I have been obtaining the appropriate data and checking it out and assembling in my primary GIS application Global Mapper. The CFS3 terrain SDK is certainly making sense now. However I still have to check out all the SDK tools. There's much work in all this & I don't want to overdo things. I also had a nasty flu virus last week which delayed matters. Hopefully I am on the mend now. Radiotherapy begins this week so I'll have less time for creative endeavours.

The data is split into 3 main types -

• topological DEM data - to produce terrain mesh.
  
• vector data - for coastlines, waterbodies, roads & rivers.
• land coverage data - for the landclass system.

The landclass side of things is still WIP at the moment. I want to take a look at the existing CFS3 landclass system & textures before moving ahead with mine. I also have to find a way to convert from USGS data to CFS3 data & line it up on the map. I will add a few new landclass types to CFS3s existing types, but not too many as that will entail a lot of additional work. I will be refering to period maps too, as land use & coverage in the Solomons area differs today from that of the 1940's http://www.lib.utexas.edu/maps/historical/pacific_islands_1943_1945.html Much of the landclass info will be hand edited in a paint program.

As to DEM data, I had originally intended to use the most recent available 3 arc second data. As this is 10 times higher resolution than the data used for CFS3, I am not sure that the CFS3 engine could cope with it over a region as large as the CFS3 European theatre. One has a number of choices : -

• use that data and then use the numbers as in CFS3 & SDK examples. This will leave any resampling downwards to the CFS3 tools. The results of such would not be known. A lot of work just to experiment.
• use SRTM30 data. This is 1km data similar to the resolution used in CFS3. However this data is more recent and accurate than the data used in CFS3.
• use the 3 arc second data & down sample the DEM data in Global Mapper. This is what I have decided on as I will be using the most recent data available.

I intend to further experiment with hi resolution data later and would love to do this also with textures, however for now, using the above approach I will be able to create a theatre the same size as the CFS3 Europe map, using the same figures in the xml files and SDK tool examples.

Vector data was a big chore last week, especially coastline data. Rivers & roads are fairly easy. For this exercise I am using vmap0 data, available from NGA via their rasterroam site. It is easy to extract this data using Global Mapper (the Swiss Knife of GIS applications.). Water body vector data is easy too. I am using SWBD data derived from SRTM data. It is good resolution, though perhaps stepped along the coast lines. I'll have to see how it looks or whether it is noticeable in the theatre.

Even though we have this data we still need vectors for the coastline, this is where the ordeal began (along with the flu), involving many hours of trial and error. I found the vmap0 & NOAA coastline data to be too lo-res & didn't line up with some of the smaller islands. The SWBD data is in area format. The coastline data has to be in lines. Global mapper's convert area to lines function caused some of the smaller islands to disappear, probably due to flaws in the data and we are still left with the problem of deleting the lines comprising the tile borders, which also deletes parts of the coastline in Global Mapper. I needed to find some other way of editing the vector data and extracting and converting to line shape data. The solution - export the vector data to dxf format & import & edit in 3DS Max (this may work too in gmax, though I haven't tried). This was somewhat unwieldy, time consuming and involved much trial & error. Eventually I got there, imported the edited DXF into Global Mapper and then re-exported as a line vector shapefile, now ready for the CFS3 sdk tools. The SDK shoreline tool is reputedly finicky & again much experimentation will be required to find the correct resolution.

A few links

DEM data is obtainable from a number of sources :-

• http://seamless.usgs.gov/ This is not the most recent data, however one can select a region for download from a seamless map intereface.
• http://srtm.csi.cgiar.org/ This is the most recent 3 arc second SRTM data available. The site also provides a link to a Google Earth interface where one can zoom in to download links. http://www.ambiotek.com/topoview (requires GE on your computer). This is the data that I used.
  
• ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM30 - global DEM data at 1km resolution.
• ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM3 - SRTM 3arc second if you know the tiles you want to download.

Other data sources :-

• http://geoengine.nga.mil/ NGA's raster roam site - both dem & vector data including vmap0 vector data
• http://www.ngdc.noaa.gov/mgg/shorelines/shorelines.html - National Geophysical Data Center (NGDC) - coastline data.
• ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SWBD/ - SWBD water body data derived from SRTM data.
• http://landcover.usgs.gov/glcc/index.php - Global Landcover data.
• http://www-gvm.jrc.it/glc2000/ - CGLC2000 - EU global land cover data.
• http://glcf.umiacs.umd.edu/data/landcover/ - GLCF - AVHRR Global Landcover Classification.

Hopefully I'll have a rudimentry theatre up and running in the next 10 days or so.

Rob