I wish to put here a renewal of the tutorial on how to make a Trainz Layout using GlobalMapper. It was made by my fellow trainzer rick1958 based on the instructions collected from me and various other sources.
Steps to make a Trainz Map using Global Mapper
-Download topo maps (in geotiff format) for the area from National Map Viewer or archive.org
-Open the map in GlobalMapper
-Crop the maps (from Tools-Control Center-Options-Cropping-Automatically Crop Collar) to have no borders
-Rectify the projection (to UTM) and the datum (to WGS84) (the zone is automatically displayed according to the place's longitude) (from Tools-Configure-Projection)
-Save the project.
-Export selected portion of the map needed (from File-Export Raster) as geotiff.
-Open the resulted map in Global Mapper
-Load the NedDem 10m resolution 32 bit for that same area, directly from the existent options in the application.
-Export the DEM as geotiff (between previously selected bounds)
-Unload all files from GlobalMapper
-Open just the DEM
-Export it as .xyz file by selecting File-Export Elevation Grid format-XYZ Grid-Option-Space (from Coordinate Offset/Scale-Scale Factors for X Y Z values different values can be introduced for smaller scaled maps: 0.1 for 1p10, 0.25 for 1/4, 0.5 for 1/2 and so on; Offset values can be introduce for various longitudinal, latitudinal or altitudinal corrections)
-Open the .xyz in hog
-Export it as a .tga file
-Open the resulted .tga file in irfanview to see the dimensions in pixels
-Open the geotiff map in irfanview to reduce it at the same dimensions
-Crop both the .tga files (dem and map) in IrfanView (from Edit-Create custom selection) to fit according with trainz boards (a board is 72px). So you must have the length and the width divisible with 72.
-Add 4 px to the length and width for map margins
-For the map textures, create a separate .tga map file
-Open in Photoshop (from Image-Mode-Indexed Color-Palette-Custom-Trainz.act) or Paint.net (from Adjustments-Hue/Saturation or from a lot of other functions available) to simplify the colours
-Open the file again in Irfanview to increase colors depth (from Image-Increase color depth)
-Load the resulted .tga files in hog
-Export the .gnd file
-Create a New Map in Trainz, then open it in the Content manager and replace the gnd file with the newer one.
-Create a one board map in Trainz and merge it the New Map to have a backward compatibility.