I should have had written 1600 * 1600 Meter textures. These are the usual 1024*1024 pixel textures. There are other 800 * 800 Meter textures, i think they are 256 * 256 pixel, but they are not longer used and objectset does not support them.
The thing with the map_tBig.tga is confusing and possibly wasn't the best idea. This is just a renamed map_t.tga, but you can, but must not, enlarge it. But the enlarement factor is needed in the ini file (No enlargement = 1). The idea was: As you mentioned the resolution of the original map_t.tga is 200 meter. That means, that the population painted in the map_t is cutted in 200 * 200 Meter pieces and when using a well populated template this means knife cutted population edges:
++++++++ ++
++ ++ ++++ +
+++ + ++ +++
+ +++ +++ ++
+ +++ ++++ +
(+ = object)
If you enlarge the map_t (copied and renamed as map_tBig.tga), the resolution is higher. So you can paint in the map_t (map_tBig) the areas to populate with an resulution of 100, 50 or even 25 meter, as one texture pixel in the map_t (map_tBig) then has just that higher resolution depending on the enlargement factor. The population edges with an enlargement factor of 2 may than look like this:
+ ++ +
+++ ++++++
++ ++ ++++
+++ ++
+ + + +
But the problem is, the textures themselves still show up with a resolution of 200 * 200 meter in the game, and this means, they will not be complitly filled with objects or objects will be placed in areas without the underlaying texture.
An other point is the overblending area of one texture to the next one of, if i remember well, 100 meters. Within 50 meters one texture will dominate, then the other, but you will still see the other texture. So when using a city texture with dense streets or other landmarks neighbouring to an agriculturel texture, you will still see the roads or landmarks when the abricultural texture starts, but these parts will not be populated. You can avoid this using an enlargement factor of 4 with the map_t, but this is quite difficulty -). I used this with my NW-Europe map, but this may be a kind of over engeneering.
With my Kasserine map i used an enlargement factor of 8 to spray these little clusters of just a few objects around the cities using the city template with a resolution 25 Meter/factor 8 (No city unterlaying city texture is used here in the final map_t) and to avoid this cutting knife effect with the city boarders themselves. But as the city texture showing up in the map is still 200 * 200 Meter, i tried to give it a "litte gardens and fields all arround"-look. Well, over all, this enlargement thing may give the best results if no texture is used in the final map_t for small buildings conglomerations :-) . But objectset also works with a just renamed map_t.