Software for field work: collecting survey data (multi-platform, on-line and off-line) As part of an RCT, I am looking for Software to record digitally the answers some survey questionnaires. The questionnaire is somewhat long,  ~100 questions  divided into 10 blocks.
We will collect  3 rounds (baseline, follow-up 1 and 2) of 600 surveys. Surveyors have access to a windows laptop and perhaps an Android or iPhone. 

Desired features:


Must function online and offline (as in some places there won´t be internet access).
Must have a functionality to skip questions. Ex: if q1=no, then skip to question 7
Preferably multi-platform (Android, OS and Windows)
Fast to set-up infrastructure and create the questionnaire
Free or reasonably cheap service
Ability to record GPS coordinates (in case of phone survey)
Ability to add Pictures (in case of phone survey)


What do most working on RCTs use?
Do JPAL, IPA and similar outfits have any recommendations on this front?
I've worked in 2015 on a survey collecting ~300 answers from 130 different countries. We had similar requirements to what you described, with multilanguage functionality on top. it was not a RCT (Randomized Controlled Trial), we were surveying on conditions of work. 

We ended up using SurveyMonkey which costed 900€ and had only the online functionality, which is a mobile optimized web page survey (compatible with any system), very fast to set up and with the ability to skip questions and add pictures. We could not capture GPS data (never heard of surveys doing that), but we could get the IP address of respondents, which can be a proxy for their location. Pictures were also possible to add, but we used it only to brand the survey.
We used Word-files via email for "offline answers", which we then manually inserted back on the website. We didn't have much field work, but I know it would have worked great to fill the survey in a phone or tablet easily, as long as there was internet access.

The main thing that made us take SurveyMonkey vs using self-hosted open-source software like LimeSurvey was: 


The ability to set up quickly (your survey is up as soon as you insert the questions, no IT configuration time needed),
Speed of connection for respondents: our server in Europe would mean long loading times for the respondents in other continents, and SurveyMonkey has powerful servers everywhere
Text mining features for open-answers and pre-made dashboards to share quick and high-level results 


If you want to look at other providers, most of the surveys I've seen recently used Qualtrics, Typeform, SurveyMonkey or GoogleDocs.