What are the key elements that we might expect to see within mosques (Blair and Bloom 2000; Hillenbrand 1994, 31-128; 1999), which might be recognisable within the aerial photographic/satellite imagery?
There is normally a centrally located large Cathedral or Friday mosque, which was often co-located with suqs (Wheatley 2001, 237). One might expect a large courtyard space within such a complex.
There could be more than one Friday mosque within a city. At Merv, for example, there were three (loc. cit.).
There are likely to be a number of neighbourhood mosques, probably of very variable size, right down to little more than private places of worship (Wheatley 2001, 238). The lower orders of these are going to be indistinguishable from urban housing: the upper ends of the scale are likely to have substantial courtyards and prayer halls. The middle range, might have sufficiently substantial courtyards and prayer halls to distinguish them from domestic housing, but will not be clearly distinguishable from madrasas or caravanserais.
Most Friday Mosques, from the 'Abbasid period were based on a rectangular layout, with a large central courtyard, surrounded on three sides by arcades and on the fourth by a rectangular hypostyle prayer hall, opposite the entrance (Blair and Bloom 2000, 109). So are large courtyards and prayer halls a distinctive feature that we could isolate in plan? They might also be distinguishable on the basis of an asymmetrical plan, with a larger building range on one side (the prayer hall), compared to the other three sides which would have comparatively less substantial ranges of buildings.
Prayer halls are often on the opposite side of the courtyard to the main entrance, and so the identification of a larger structure on the opposite side of a substantial courtyard to a street might be seen as an indicator.
Large mosques might also be set within larger compounds: for example, see the Mosque of Abu Dulaf (Northedge 2005, fig. 97) or the Mosque of al-Mutawakkil (Northedge 2005, fig. 50), both at Samarra. Are these double enclosures a distinctive feature that might be identified in plan?