Updated read and write UBC_DCobs functions so that they are python3 compatible. Changed the ”3D”  “General” case so that it flips the sign on the z-component of Tx and Rx locs for the DCoctree code. Flipping sign was overwriting locs in original survey object so added some .copy() statements to safeguard this.
Updated read and write UBC_DCobs functions so that they are python3 compatible. Changed the ”3D”  “General” case so that it flips the sign on the z-component of Tx and Rx locs for the DCoctree code. Flipping sign was overwriting locs in original survey object so added some .copy() statements to safeguard this.

simpeg/simpeg