How it's possible ? I mean change textures.
Make a screenshots from google maps in your favourite browser zoomed almost fully in.
One step less than maximum.
(the last zoom step is mostly just enlargin the pixels, so that a waist of space).
Create a new file of 24000x24000 or so pixels in photoshop.
Than use the command paste in photoshop, the screenshot will be there on a seperate layer.
Delete the bits you dont need/want.
Go to the next part of the google maps in your browser, but have some overlap with the previous part.
Do a screen copy again, and past again in photoshop.
Than place/move the 2 layers exactly in photoshop.
Making the layer you work with a bit transparent will help to get them aligned on the pixel exactly, when aligned make it 100% again.
Remove the parts you dont want from the screenshot layer, like the navigation bar and other browser specific things.
Than you can merge those layers.
Repeat till you covered the part you need.
Than flatten all those laste parts.
(Save a extra copy of this file, just for later use, or when thing go wrong..
As stiching them together can take a few hours depending on the track.
Would be a shame to loose your work by messing up.
Open the lowres texture you want to replace, selects all and copy.
Paste it on a seperate layer in photoshop.
Make the top layer 50% transparant.
Than scale that layer with the lowres texture exactly over the highres underneath.
Crop the whole image on the size of the lowres texture.
Switch the top layer off.
Than save that image over the lowres image, replacing it basically.
Or when you already have imported those tiles in Bob's, than just replace the texture from within Bobs texure editor.
If you have multiple parts repeat this step from the base big google maps texture.
One big ground texure of 4096x4096 is no problem for a modern system.
For the seperate tiles, i would use not more 2048x2048.
Giving you a great resolution to work with.
Later you can clean up that texture, remove all objects and shadows that you dont want to see.
And you be left with a great looking groundtexture.
Depends on the track if you could use one mega texures or multiple tiles.
I just use the google earth data especialy for the parts around the track.
Creating a new ground based on the parts I imported from Earth.
So i can use much less polygons, but i still know the basic surrounding is correct.
Here some example where is used this big texture blended with a basis ground & grass texure. This is the Sachsenring.
The track itself is based on proffesional GPS data from a GT3 team.
I have only used the buildings from a excisting rF version.
As it's not finished i ask permission later..
But i might do them again too, not sure yet.