Solution:Here I am going to explain how you can achieve this:
a) You need to create two fields LAT & LON on the Zoho form where you want this information to be stored.
b) You then need to create one PHP page which you can host on external server. As Zoho doesn't provide any space to host any custom page. So you have to host this page on the external domain.
c) Now you need to use Geolocation object of HTML 5, to get the user's current location, on this PHP page.
d) In my current example I am passing the newly generated record ID on this page php via query string while calling this PHP page from Zoho form. I have divided my zoho form into two steps. In the first step I am filling all the user's details and after clicking on submit button on this step 1, I am calling this external PHP page.
e) After getting the user's latitude & longitude information, I have called Zoho's form update API and updating the record with Lat & Lon for the ID which I have received on this php page via query string. In this way you can get Latitude & Longitude of user in Zoho.
Please note that SSL should be installed on the domain where you are going to host this PHP page as without SSL you will never get Lat & Lon information.
You can check screenshots of above solution. This solution is tested on web, android & iphone. It is is working everywhere without any issue.