3

I've produced a set of topographic derivatives using both SAGA and ArcGIS. They are all in the same CRS.

When I load them into R, however, the proj4 strings are different: 

>arcRaster
class      : RasterLayer 
dimensions : 16002, 21200, 339242400  (nrow, ncol, ncell)
resolution : 10, 10  (x, y)
extent     : 480200, 692200, 4896280, 5056300  (xmin, xmax, ymin, ymax)
crs        : +proj=utm +zone=11 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0 

> sagaRaster
class      : RasterLayer 
dimensions : 16002, 21200, 339242400  (nrow, ncol, ncell)
resolution : 10, 10  (x, y)
extent     : 480200, 692200, 4896280, 5056300  (xmin, xmax, ymin, ymax)
crs        : +proj=utm +zone=11 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

Note the raster produced in saga is missing +datum=NAD83. They align properly and they stack without problems. Why is the datum information missing?

Improve this question
6
  • try to reproject data.
    – Muhammad Imran Siddique
    Mar 11, 2020 at 23:50
  • It doesn't need to be reprojected - I know they are in the same projection, it's just that there is an inconsistentcy in the proj4 string
    – Nick
    Mar 12, 2020 at 14:37
  • For example if I open both layers in ArcMap it recognizes the projections to be the same "NAD_1983_UTM_Zone_11N". It is only when loaded into R that the projections appear different. Furthermore, if i simply do crs(sagaRaster) <- crs(arcRaster) or vis versa they still align perfectly and stack. I would expect that if they were in fact different projections, simply redefining the CRS like this would cause some offset.
    – Nick
    Mar 12, 2020 at 15:35
  • check the matadata comparison gdalinfo filename
    – Muhammad Imran Siddique
    Mar 13, 2020 at 7:49
  • The datum information is there when i look with gdal info (also appear as identical coordinate system in arcmap)
    – Nick
    Mar 13, 2020 at 22:23

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Browse other questions tagged or ask your own question.