I have a globe mesh model like the one seen in google earth.
I wonder if there is a common way, like formula or api for unity, to convert the geolocation (altitude, longitude) to be located for the globe model.

Do you mean spherical coordinates, like for a simple sphere (http://en.wikipedia.org/wiki/Spherical_coordinate_system), or real-live coordinates? Real-live coordinates can get pretty involved depending on how detailed you need to get. Look into Mercator projection, UTM (http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system) etc.

The simplest form is

x = r * sin (lat) * cos (lon)
y = r * sin (lat) * sin (lon)
z = r * cos (lat)

where r is radius (altitude = r + height_above_r)
lon is longitude
lat is latitude

This may all be off by 90 degrees depending on your orientation