Spatial profiles of normalized emission line intensities observed in the Horsehead nebula, compared to predictions from Meudon PDR model with P_th = 4 × 10⁶ K cm⁻³ and G₀ = 100, wrapped in a locally spherical cloud with curvature radius R_C = 0.05 pc. The profiles are convolved to the native angular resolution of the tracer maps. On this figure, the radiation field comes from the right. We observed a significant shift between the observed H₂O profile and the model, the latter being much deeper in the cloud.