Hi,
Through INSPIRE more and more free available Digital Elevation Models are available in Europe (http://www.opendem.info/opendemsearcher.html).
Unfortunately all countrys use their own reference system (also vertical!) and it is a hard job to dowlnload the data which is mostly split in small parts. 
So the creation of an unified DEM would make sense (help wanted!).
The idea is:
- Convert every dataset to the European reference system 4258
- Mosaic the datasets and produce the usual 1°*1° tilesets
- If a tileset is not completely covered by the country(s) dataset(s) the “voids” are filled with the EU-DEM (http://www.eea.europa.eu/data-and-maps/data/eu-dem, which is a Surface Model
- When mosaicing the data, allways the highest resolution is taken into account
- Point clouds would be sampled to regular grids
- Create the proper attributation of the distributor(s) for every tile
The product:
- 1°**1° tiles with the with the highest accuray in EPSG 4258
Do you also need 1°*1° tiles in 4326? Which resolution (30m,the highest, other)?
Is there any free software which take gps epoch into accout?
4326 and 4258 were the same in 1989, but since then Eurasia is shifting to NE ~ 2,4 cm/a.
For GPS data this does not matter, but for a 1m DTM this could matter.
Every dataset has to be proper cited by the user!
This means when you would use a shaded map based on the dataset for whole europe in your webclient, you have to show at this point in time the information about 35 distributors. I think this could be easily done with the usally (i) attributation button in OpenLayers for example. What is your opinion.
Best