What is the map projection of the THEMIS images?

The THEMIS Standard Data products (EDR, RDR, ABR, & BTR) are not projected into any coordinate system. The pixels in these products maintain the time, row, and column ordering (per band) of the raw observation; this arrangement is commonly referred to as "camera coordinates". Be aware that the bands of the QUBE products are not spatially registered within a single image.

The THEMIS Special Projected Products (GEO, ALB, PBT, RGB, and DCS) are map projected, with the coordinate system details documented in the headers and/or available labels. See the available documentation for all projection parameters, but the following guidelines will get you started:

  • EQR = EQUIRECTANGULAR, where -60 < center-latitude < +60 (this is a variation of the Simple Cylindrical projection)
  • POL = POLAR STEREOGRAPHIC, where max-latitude > +60 OR min-latitude < -60
  • SNU = SINUSOIDAL, where -60 < center-latitude < +60
  • IR-PBT, VIS-ALB & IR-DCS, VIS-RGB maintain the projection of the source GEO product

Note: there are significant improvements to the THEMIS camera models in ISIS-3; if you have the choice, use ISIS-3 projected products over ISIS-2 projected products.