Displaying user polygons on location_cck gmap locpick widget

Hi,

I have a content-type 'observations' that includes gmap location picker from location_cck.
Users can set observation's coordinates with this widget.
Users also owns other content-type that are represented as polygons.
I would like to fill the location_cck gmap with their polygons and thanks to autozoom property having the map centered on their activity area.

I have seen the gmap macro textarea in admin/content/node-type/observation/fields/field_location but cannot figure how it works. I also have no idea if php can be enbeded into it ?

Can someone help in :
- clarifying what this setting is made for, how it works ?
- helping me in building my content-type as expected ?

Thanks,
Ed