[R-sig-Geo] NASA's Black Marble monthly data: Reprojection isn't accurate

[Michael Sumner]

The extent of this one is

70, 80, 10, 20

Later versions of GDAL determine this automatically (I'm not sure when)

 rast("VNP46A3.A2018091.h25v07.001.2021125122857.h5")
class       : SpatRaster
dimensions  : 2400, 2400, 26  (nrow, ncol, nlyr)
resolution  : 0.004166667, 0.004166667  (x, y)
extent      : 70, 80, 10, 20  (xmin, xmax, ymin, ymax)
coord. ref. : lon/lat Unknown datum based upon the GRS 1980 Authalic Sphere
ellipsoid
sources     :
VNP46A3.A2018091.h25v07.001.2021125122857.h5://AllAngle_Composite_Snow_Covered

VNP46A3.A2018091.h25v07.001.2021125122857.h5://AllAngle_Composite_Snow_Covered_Num

VNP46A3.A2018091.h25v07.001.2021125122857.h5://AllAngle_Composite_Snow_Covered_Quality
              ... and 23 more source(s)
varnames    : AllAngle_Composite_Snow_Covered
              AllAngle_Composite_Snow_Covered_Num
              AllAngle_Composite_Snow_Covered_Quality
              ...

Be very careful with canned steps to "fix" georeferencing, make sure it
needs fixing and check that it's right. Ultimately the best way to "fix" it
is to go to the source of the code that interfaces the data, which here is
GDAL and report there - but clearly that's been updated from whatever
version was in use on stackoverflow.

Cheers, Mike
.





On Sun, Sep 10, 2023 at 1:17 AM Nikolaos Tziokas <nikos.tziokas using gmail.com>
wrote:

> I downloaded NASA's Black Marble monthly nighttime light NTL data, VNP46A3
> <
> https://ladsweb.modaps.eosdis.nasa.gov/missions-and-measurements/products/VNP46A3/
> >.
> In a previous question
> <
> https://gis.stackexchange.com/questions/466571/extent-not-found-on-nasas-black-marble-monthly-images-how-to-set-it/466574?noredirect=1#comment761916_466574
> >
> of mine the reprojection worked perfectly but now it seems that it doesn't.
> For example, I wanted to download NTL data for the city of Mumbai, India.
> After reprojecting the NTL (product 5 (All_Angles_Snow_Free) from the .h5)
> the result is attached here
> <https://drive.google.com/drive/folders/1V115zpdU2-5fXssI6iWv_F6aNu4E5qA7
> >.
>
> At the bottom if the image is a shp of Mumbai (downloaded from GADM) and
> the red circle in the top indicates where Mumbai is in the NTL image.
> Clearly something's not right.
>
> I downloaded the image from here
> <
> https://ladsweb.modaps.eosdis.nasa.gov/missions-and-measurements/products/VNP46A3/
> >
> (LAADS-DAAC, Level-1 and Atmosphere Archive & Distribution System
> Distributed Active Archive Center). The code I used to extract the NTL
> radiance image is:
>
> library(terra)
>
> wd <- "path/"
>
> r <- rast(paste0(wd, "VNP46A3.A2018091.h25v07.001.2021125122857.h5"))
> crs(r) <- "epsg:4326"
>
> 2400*(15/(60*60))
>
> h = 25
> v = 7
>
> ext(r) = c(-180+h*10,-180+(h+1)*10, (v-2)*10,(v-1)*10)
>
> ntl <- r[[5]]
>
> writeRaster(ntl, paste0(wd, "ntl.tif"), overwrite = TRUE)
>
> Why the code worked perfectly in the previous question and now it doesn't?
> From here
> <https://drive.google.com/drive/folders/1V115zpdU2-5fXssI6iWv_F6aNu4E5qA7>
> you can download the .h5 image if you don't want to use NASA's website. I
> am using R 4.3.1 and RStudio 2023.06.2+561.
>
> --
> Tziokas Nikolaos
> Cartographer
>
> Tel:(+44)07561120302
> LinkedIn <http://linkedin.com/in/nikolaos-tziokas-896081130>
>
>         [[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo using r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>


-- 
Michael Sumner
Software and Database Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner using gmail.com

	[[alternative HTML version deleted]]