DM-10105: Avoid loss of precision in Wcs persistence. #212
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parejkoj
approved these changes
Apr 5, 2017
| with lsst.utils.tests.getTempFilePath(".fits") as fileName: | ||
| wcs1.writeFits(fileName) | ||
| wcs2 = lsst.afw.image.Wcs.readFits(fileName) | ||
| self.assertEqual(wcs1, wcs2) |
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👍 Exact equality here is probably good.
| @@ -1082,7 +1082,8 @@ void Wcs::write(OutputArchiveHandle & handle) const { | |||
| WcsPersistenceHelper const & keys = WcsPersistenceHelper::get(); | |||
| afw::table::BaseCatalog catalog = handle.makeCatalog(keys.schema); | |||
| PTR(afw::table::BaseRecord) record = catalog.addNew(); | |||
| record->set(keys.crval, getSkyOrigin()->getPosition(afw::geom::degrees)); | |||
| record->set(keys.crval.getX(), _wcsInfo[0].crval[0]); | |||
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It's sad that we can't use our Sky methods, but I guess it makes sense to do it this way in the internals.
The old implementation round-tripped CRVAL through radians because it used Angle, which resulted in a loss of precision and inexactly persisted WCSs.
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The old implementation round-tripped CRVAL through radians because it used Angle, which resulted in a loss of precision and inexactly persisted WCSs.