we have troubles in installing the GEOS library on heroku cedar stack.
We followed this guide: https://devcenter.spacialdb.com/Heroku.html and it didn't work.
We noticed that the path (/app/tmp/geos) stored in the provided geos binaries was wrong, so we built our own binaries with vulcan.
We changed parameters (BUNDLE_BUILD__RGEO) accordingly, but we weren't able to make it work.
We even hardcoded geos paths in our custom rgeo gem without any success
We also tried other buildscripts (https://github.com/roximity/heroku-buildpack-ruby-geos) but they are too old and it will be difficult to keep them up to date with heroku's one
We are using ruby 2.0.0-p195 and Rails 3.2.13
I just created heroku-buildpack-rgeo-prep to address this problem.
This buildpack overwrites .bundle/config to set BUNDLE_BUILD__RGEO to the current build path. Unfortunately, you can't set BUNDLE_BUILD_RGEO=/app because your project is actually built somewhere like /tmp/build_1890cktlpat5d.
Hopefully, this buildpack will make it much less painful to use RGeo on Heroku.