Reducing extent of map

Hi.

I’m making a specific map for the Pennine Way and have found contours and the osm data files i need. The problem is that the contour .img’s are for the whole of Great Britain + Ireland and when viewing the map in BaseCamp i get a lot more than i need.

Is there a way of telling mkgmap the bounds i want the finished gmapsupp.img to have? (The contours come as premade .img’s)

Thanks in advance for any help.

Did you try http://extract.bbbike.org/#

You can split the contour data if they are in pbf format with osmconvert:
http://develop.freizeitkarte-osm.de/
http://wiki.openstreetmap.org/wiki/Osmconvert#Clipping_based_on_Longitude_and_Latitude

This data you can then merge with osm data with osmconvert like this:
osmconvert.exe map.osm.pbf contours.o5m -o=map_with_contours.o5m