SRTM Data
On the Internet, there is a wide choice of SRTM data. Some are very rough and with a lot of holes. To find the best file for a given area some experiment must be done.
The criteria of WildAlps are:
No holes,
No smoothed area which comes from an issue with the radar recording system.
Altitudes must be adequate for mountains and the beds of valleys.
These criteria can be selected with 3DEM.
Crests must be as knife edge and bed of rivers as linear as possible.
This can only be checked with some experiment.
There is a general smoothing of all the landscape during the conversion from WGS84 to UTM. The top of the mountains will be lowered and the beds of valleys will be raised.
A good criterion is a general smoothing less than 3%.
But, with a square mesh of 90 m, narrow peaks will be missing or aborted, even with very good SRTM data, as Provence 2 or YAlps. So some hand tweaking must be done in the .trn files, to get a realistic landscape. For example in Wild Alps "Aiguille du Midi" had been reshaped, note that in reality there are 3 peaks in less than a square of 90 m, and "Dent du Géant" had been created. But, this 2 characteristics peaks can't be missed in the panorama of the Mont-Blanc's range.
Other minor tweaking had been made everywhere it seems necessary.
Terragen
Basic texturing of tiles are made with Terragen. Since YAlps the world file of Terragen had been upgraded to master the green colors. But it's long way to mix green of fields, forests, mountains pastures and transition with snow.
Open Street Map Data
Open street Map data are free, and the quality of these data are fair, except with rivers, where you can find a wide range of quality from poor to excellent. The data are imported tiles by tiles.
Filtering of data is not so difficult but necessary.
The mixing of these data with Terragen tiles is easy, if the scaling and the positioning with the first tile is correctly done. The synchronizing of data with other tiles is very easy.
The texturing of these data, principally for buildings, roofs of different colors, white facade, transparent shadow, treated in "Trompe l'oeil" enhance the 3D wiew. The embedding of OSM data in Terragen tiles don't change the FPS in Condor.
Scaling
All the data, streets, roads, buildings, rivers, and all 3D objects are correctly scaled. The use of high pixel resolution (8192 x 8192) allow a correct scaling which is quite impossible with lower resolution. Compare with Google Earth in 3D.
Airports
All airports of the scenery had been modeled like there real appearance (Taxiways, hangars etc..). Sion and Aosta are unfinished. Probably, high or big buildings, surrounding the airport must be added in airports files. Megeve Altiport, is done in the way of bumpy airports with a short flat area at the high ends. Some tweaking was also necessary to smooth the embedded runway. Hangar textures are simplified and should be enhanced.
Thermal map
The thermal map, developed with Terragen, is more predictive than stochastic. Hand corrected with hot spots and with a magnified contrast, the thermal map give a good result and seem more natural.
Coupled with good SRTM Data, the lift response in ridge flight is better, and the wind speed can be reduced.
What next with WildAlps
WildAlps is an expandable scenery in all directions. The 16 Terragen tiles of WildAlps 1 are already reused in a wider scenery. It is only a question of rows and columns and some calculations.
The prototype of a 100 Terragen tiles scenery (from Milan to Challes les Eaux) is working properly.
Only the OSM data must be added to Terragen tiles and airports must be also modeled.
It is a long job, but a lot of work can be automated.
Rendez-vous at the summit of "Aiguille du midi" for a step into the void.
Have fun!
