JCMT spectra of ortho-H₂D⁺ J_KK′:1₁₀−1₁₁ (top row, velocity axis from 1 to 6 km s⁻¹), and APEX spectra of para-D₂H⁺ J_KK′:1₁₀−1₀₁ (middle row, velocity axis from 1 to 6 km s⁻¹) across the cloud (the position of the cut is indicated in Fig. 2). Gaussian fits are overlaid in red and green, respectively. The same Gaussian fits with same colour code are reproduced in the bottom row, after normalization to the peak temperature for the +7″ spectrum, for a better comparison of the ratio variation and linewidth differences between the two isotopologues.