1. Introduction

2. Data & Methods
2.1. Gaussian decomposition of the GRS
2.2. Bayesian distance calculator

3. Distance estimation
3.1. Modification of the BDC and setting of prior weights
3.2. Prior for the kinematic distance ambiguity
3.3. Prior for the fitted linewidth
3.4. Choice of distance solution

4. Galactic distribution of the gas emission
4.1. Catalogue description
4.2. Face-on view of the 13CO emission
4.3. Comparison of the distance results
4.4. Gas fraction in spiral arm and interarm regions
4.5. Velocity dispersion in spiral arm and interarm regions
4.6. Galactic to centric variation of the gas properties
4.7. Vertical distribution of the 13CO emission
4.8. Potential problems, artefacts, and biases
4.9. Comparison with previous results

5. Conclusions