Within GeoExpress 7 can custom projections be defined?

[mitchelljj]

Within GeoExpress 7 can custom projections be defined and then files be inputted with this custom projection which are used as source for a MrSid mosaic which is also reprojected to another projection at the same time?

Also if the above is true then what is done first the mosaicking or the reprojection?

[rparker]

Yes, you can define custom projections using the WKT format or by importing a .prj file from ESRI. When building a mosaic and reprojecting, the raw pixels are worked with and both are done at the same time. I would say that reprojection is done first internally.