PhD in GIS after Bachelor Degree in Computer Science I have a bachelors degree in Computer Science &amp; Engineering and have specific experience in geographic information systems (GIS). I am planning to enroll in a GIS PhD program and have searched for United States universities with GIS PhD programs. However, none of these PhD programs are offered from a Computer Science department: all programs are in either a Geography department or Civil Engineering department or Earth Science department. Should I apply to these other departments even though I come from a Computer Science background? 

Can a student complete his PhD program in a university department other then the department of his undergraduate work?
When you go to a mainly geographic department, you will have to study courses for projections, spatial databases, geo-servers and mapping frameworks, which you already probably know through your job. Geographic departments have people without a programming background and therefore these people have to be trained almost from scratch, so they can do this type of research. On the other hand, many of these departments have some relatively young professors with a CS background who are really looking forward to work with CS people like you (instead of geographers) to mainly progress their research. In that sense, I am sure you can be accepted at such a program but prepare to have to take courses on things you are already familiar with. 

On the other hand there are many "pure" CS professors, working on "pure" CS departments, who also do GIS related research. If you look at more CS focused GIS conferences, like ACM SIGSPATIAL GIS you will find many papers by mainly CS people on GIS related subjects. So, you can search for possible advisors there, by looking at the papers that get published in such venues in the last 2-3 years. If you find some papers that deal with subjects that you are interested in, you can find out in what universities the authors work, perhaps contact them (advice on how to approach potential advisors is scattered everywhere on this site) and take it from there. It does not always matter the "title" of the PHD (if it says GIS or not) but IHMO it is more important to work with people that do interesting things, close to your interests. So, do not exclude the possibility to do GIS research on a pure CS department.