Version 1 (modified by mggr, 15 years ago) (diff)


Q: Why are my geocorrected files upside down? / Do I need to manually rotate images to make north "up"?



Flight lines in level 1 data are as the sensor sees them (ie. appearing in the order seen by the sensor). If the aircraft is flying south, the first lines in the data will be the most northerly with later lines further south. If the plane is flying east, the first lines will be the most westerly, with later lines heading east. Navigation data is included with the level 1 imagery and can be used when producing level 3 georeferenced images. You don't need to do any manual rotation to compensate for flight direction yourself when making level 3 images - that's all handled by azgcorr.

Level 3 images are corrected for flight direction and will appear with north up in any viewer that reads the georeferencing information correctly (e.g. ENVI).

You'll see the flight lines run south to north in the level 1 data, but when they're processed to level 3 (georectified, via azgcorr), they'll be correctly oriented with north at the top (depending on your viewer, ENVI should be fine). When it works anyway!

If you're still seeing the images upside down when you're looking at level 3 images, let us know what viewer you're using and what file format - this implies you're not getting the georeferencing information correctly.

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