jdries
commented
10 months ago Found a simple test that exposes the issue. It's all about gridextents that are in fact aligned, but due to very small numerical differences, things go wrong. Still have to figure out where and how to integrate this as part of geotrellis unit tests.
val targetBounds = GridBounds(55L,103,55+73,103+111)
val ge = GridExtent[Long](Extent(1.8973214288275528, 49.352678585684544, 6.299107143119465, 51.7276785856839), CellSize(0.008928571428584,0.008928571428568996))
val targetExtent = ge.extentFor(targetBounds)
//second, aligned extent based on a LayoutDefinition
val ge2 = GridExtent[Long](Extent(2.3883928573996727, 49.66517858568254, 3.5312500002584244, 50.80803572854129), CellSize(0.008928571428583998,0.008928571428583998))
//gridextents have to be aligned for test to be valid
//basically copy of geotrellis.layer.LayoutTileSource#requireGridAligned
requireGridAligned(ge,ge2)
val resultingBounds = ge2.gridBoundsFor(targetExtent)
assertEquals(targetBounds.height,resultingBounds.height)
assertEquals(targetBounds.width,resultingBounds.width)
pomadchin
Overview
When working in epsg:4326 coordinates, I recently observed separate bugs caused by the same problem. Basically transformations between geographical coordinates and grid coordinates where wrong due to floating point imprecision. In both cases, grid coordinates were calculated as doubles and resulted in e.g. 4.9999999 but were done floored (toLong) resulting in 4.
This resulted in an actual pixel shift in one case, and in another case a missing row of pixels at the bottom of a saved geotiff.
Checklist
Notes
Optional. Ancillary topics, caveats, alternative strategies that didn't work out, anything else.
Closes #XXX