If you can open the data you need in ENVI, then you can do the following to perform a *rough* georeferencing. - Go to File->Edit ENVI Header and select the dataset you just opened - Click on Edit Attributes and select Geographic Corners, then click the DMSDD button. - Enter the pixel and map coordinates for the four corners. For example, the upper left corner for your image would be ImageX:1.0, ImageY:1.0, Lat:50.0, Lon:-180.0 - When done, click OK twice. Then go to File->Save File As->ENVI Standard and save the georeferenced result. If you don't you'll have to enter the four corners again the next time you open the HDF. This process creates a pseudo Geographic Lat/Lon projection with a WGS-84 datum, so the accuracy isn't fantastic--but it's the best you can do with only four tie points. You could increase the accuracy by carrying out an Image to Map registration process.