No, with ContentMap you can not enter the coordinates in an article from Frontend, but you must login to Joomla Administration. We recommend using the new ACL of Joomla 2.5 that allows you to simply manage access levels, so as to give authors of the articles of your site restricted administration of Joomla where they can only submit articles, and maybe even limit in which categories they can write. In this way they will also complete the field for the coordinates of ContentMap.

On there is a useful guide: ACL Action Permission Examples