Correction to: Medium-scale traveling ionospheric disturbances by three-dimensional ionospheric GPS tomography

Correction to: Earth Planets Space (2016) 68:32 https://doi.org/10.1186/s40623-016-0412-6

In the original publication of this article (Chen et al. 2016), the author found a typo error in Eq. (8) in the section of Appendix. The correct constraint matrix, W, should be given as:

$$ w = \left[ {\begin{array}{*{20}c} {\sum\limits_{j = 1}^{6} {C_{1,j} } } & { - C_{1,1} } & { - C_{1,2} } & { - C_{1,3} } & { - C_{1,4} } & { - C_{1,5} } & { - C_{1,6} } & {} & {} & {} & {} \\ {} & {\sum\limits_{j = 1}^{6} {C_{2,j} } } & { - C_{2,1} } & { - C_{2,1} } & { - C_{2,1} } & { - C_{2,1} } & { - C_{2,1} } & { - C_{2,1} } & {} & 0 & {} \\ {} & {} & {} & {} & {} & \ddots & {} & {} & {} & {} & {} \\ {} & 0 & {} & {\sum\limits_{j = 1}^{6} {C_{N - 1,j} } } & { - C_{N - 1,1} } & { - C_{N - 1,2} } & { - C_{N - 1,3} } & { - C_{N - 1,4} } & { - C_{N - 1,5} } & { - C_{N - 1,6} } & {} \\ {} & {} & {} & {} & {\sum\limits_{j = 1}^{6} {C_{N,j} } } & { - C_{N,1} } & { - C_{N,2} } & { - C_{N,3} } & { - C_{N,4} } & { - C_{N,5} } & { - C_{N,6} } \\ \end{array} } \right] $$

(8)