[BillC]

cjakeman, on 27 January 2017 - 12:22 PM, said:

...... It just assumes tiles which are 2048m square. The tiles could be generated by any convenient projection. And, yes, UTM would be a more useful projection, especially for importing elevation and path data.

What you are alluding to is the Plate Carree projection. As James has mention the problem is not with specifying a particular Lat. Long. specification in degree coordinates, but in projecting them on a flat screen (plane surface). Most GIS date on the world scale is WGS84, which is based on GPS satellite data. However for combining GIS data from a verity of sources a common, standard reference is needed (datum). Such data may may be for instance USGS topo in NAD format, combined with DEM, which is in UTM format. Such to combine these sources a common reference is needed. A useful reference on comparing projections is this ArgGis manual. Open source programs QGIS/GDAL/GRASS are bascally clones of ArcGIS.

Trainz actually uses Plate Carree as it's base maps, just not the same dimensions as MSTS. The exact value escapes me at the moment but I believe it's around 970m x 970m. TransDem coverts different map sources to UTM, then tiles them to the base map.

[cjakeman]

BillC, on 27 January 2017 - 04:19 PM, said:

However for combining GIS data from a variety of sources a common, standard reference is needed (datum). Such data may may be for instance USGS topo in NAD format, combined with DEM, which is in UTM format.

Indeed it is, and thanks for providing more detail.

My point was that very little change to the code is needed to give Open Rails a different projection. What we do need, though, to build new routes is a replacement for RGE and DEMEX so that we can easily create a set of tiles iin a convenient projection with real elevation data and feed these to a Route Editor.

[Lindsayts]

Goku, on 27 January 2017 - 12:31 PM, said:

UTM is bad choice. Maybe better than IGH but still bad. Only reasonable choice is Mercator projection used in all online maps and WMS image servers.

There's NO perfect projection, UTM's only real limitation is the area it can cover in a single instance, this is unlimited in a north south direction but is limited to around plus or minus 4 or 5 degrees of longiude in the east west direction and its VERY unlikely anyone will build a route that big. A single instance of UTM would just cover the main island of england Scotland and Wales.

Mercator projection is not an equal area projection, ie differing areas of the world are at different scales, also in this projection the world scales uniformly in a north south direction but in the east west direction the scale varies with latitude making it completely unsuitable for a train sim.

LIndsay

[Lindsayts]

cjakeman, on 28 January 2017 - 11:31 AM, said:

Indeed it is, and thanks for providing more detail.

My point was that very little change to the code is needed to give Open Rails a different projection. What we do need, though, to build new routes is a replacement for RGE and DEMEX so that we can easily create a set of tiles iin a convenient projection with real elevation data and feed these to a Route Editor.

Have a look at Netpbm set of tools for a POSSIBLE basis for a replacement of DEMEX. Netpbm being a set of GPL ed unix tools (for which the source is readily availible) for image manipulation and there is almost nothing one cannot do with these tools to a rectangular block of data. I am NOT saying to run linux but picking the tools required from the set build the program in WIndows.

The particular program of the set I am thinking of is "pamscale", THis will scale a png image via any specfied amount either only horizontal or vertical or both and supersample (via a selectable filter function) to create intermediate points if required. I have used this program to create terrain for may own use, you do have to play with the filter functions a bit, some working better than others, but the produced terrain was quite usable.

Lindsay

[Jovet]

cjakeman, on 28 January 2017 - 11:31 AM, said:

What we do need, though, to build new routes is a replacement for RGE and DEMEX so that we can easily create a set of tiles iin a convenient projection with real elevation data and feed these to a Route Editor.

I have no stake in this conversation (debate), but I would like to point out that I hope such functionality is integral to such a route editor itself. Having separate software to do these different tasks is clumsy and inelegant. Just as I would like to see a route editing mode from within the simulation (similar to RS/TS20XX), adding/removing tiles and terrain and managing topography data should be accomplished from within the single editor.

[Goku]

cjakeman, on 28 January 2017 - 11:31 AM, said:

replacement for RGE and DEMEX so that we can easily create a set of tiles iin a convenient projection with real elevation data and feed these to a Route Editor.

If someone only wants to create simple tiles with real elevation data, TSRE is good replacement for RGE+DEMEX.

[Goku]

Lindsayts, on 28 January 2017 - 12:53 PM, said:

Mercator projection is not an equal area projection, ie differing areas of the world are at different scales, also in this projection the world scales uniformly in a north south direction but in the east west direction the scale varies with latitude making it completely unsuitable for a train sim.

But you can define center point for a route and differences in Mercator won't be big over average route size. I think bad angles is most annoying thing and only Mercator allows for good angles.

[Hamza97]

Trainz board is 720*720m...

[Lindsayts]

Goku, on 28 January 2017 - 01:55 PM, said:

But you can define center point for a route and differences in Mercator won't be big over average route size. I think bad angles is most annoying thing and only Mercator allows for good angles.

Both Mercator and Transverse Mercator share the same mathematical base so are very alike, both projections are conformal, that is they preeserve local shapes correctly . Both are limited in the area they cover and one can only move so far from the reference co-ordinate before distortion becomes a factor. In both cases the area is much greater than any route will be.

[cjakeman]

Goku, on 28 January 2017 - 01:52 PM, said:

If someone only wants to create simple tiles with real elevation data, TSRE is good replacement for RGE+DEMEX.

I didn't know that TSRE was able to do this. Must give it a try.