SRTM data import

hi everyone,

i discovered heron recently and i use it to import shapes files and srtm data. the both need to be precisly superimposed. 

I manage to do this by setting the rhino zero to the WGS84 coords of the bottom left corner of my SRTM file, and just adding the shape with the heron component in charge of it.

But i was troubled by the boundaries of the SRTM : when i set a rectangle with exaclty 1°Lon and 1°Lat (which are in my lat : {78.58245, 111.132366} [km]) the component fail, saying "index out of range", and that even if that same component is telling me that my SRTM file has a topoextent of "Rectangle (w=78.647935, h=111.224977) [km]" 

i calculate the difference which are respectivly 65.485m and 92.611, and it appears to be exactly 3". I then figured out that it was the overlapping zone of the SRTM file.

so my questions are :

1 - How heron is dealing with this overlapping zone ? does it deletes them ?

2,3 - As i figured out that there is only 2 side of the 4 which are overlapped, in France it seems te be the North and Est sides i am right ? And is it the same everywhere else ?

4,5 - How can i be sure to load the entire tile ? And the same for the shape files ? 

thanks