1

I am trying to use a .tif file from USDA's CropScape, which has the proj4 string

"+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0"

Creating the original raster object succeeds and is plottable, but comes along with the error message

"Warning message: In .newCRS(value) : +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0 is not a valid PROJ.4 CRS string"

Likewise, trying to manually assign the CRS by typing

crs(cropscape) <- "proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0"

does not work and returns a similar error message, that it is not a valid PROJ.4 CRS string.

I'm no CRS or PROJ4 genius but I do not see what is wrong with this string. What is the problem here?

For reproducability: this is the code being used to generate the cropscape raster object:

cropscape <- GET(url="https://nassgeodata.gmu.edu",
                 path="axis2/services/CDLService/GetCDLFile?year=2014&fips=06") %>%
  content('text') %>%
  str_remove(".*<returnURL>") %>%
  str_remove("</returnURL>.*") %>%
  raster()
7
  • Where does GET and the %>% operator come from? – Spacedman Aug 23 '20 at 21:45
  • Sorry, GET is from package httr and is being used to interface with the cropscape API. %>% is a piping operator from dplyr. – user168982 Aug 23 '20 at 21:59
  • and str_remove? If you are going for reproducibility you do need to tell us all the add-on packages. – Spacedman Aug 23 '20 at 22:17
  • from stringr, also a part of tidyverse. Sorry for not including this off the bat, I was under the impression that tidyverse was universal enough that these would be recognized. GET pulls the info from the API, content strips everything but the text, which is a string from which I want just a url that is surrounded by <returnURL> and </returnURL> tags – user168982 Aug 23 '20 at 22:35
  • No, its not universal! And anyway, doing library(tidyverse) is never a good idea - best practice is to always use as few packages as possible and get each one with a separate library call. – Spacedman Aug 24 '20 at 7:15
1

Your CRS:

> crs(r) <- "proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0"
Warning message:
In .newCRS(value) :
  proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0 is not a valid PROJ.4 CRS string

Works if you add a + sign at the start:

> crs(r) <- "+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0"
> 

Interestingly the sf package seems to cope with it:

> pts = st_as_sf(data.frame(x=1,y=1),coords=1:2)
> st_crs(pts) <- "proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0"

but is silently setting the CRS to NA:

> pts
Simple feature collection with 1 feature and 0 fields
geometry type:  POINT
dimension:      XY
bbox:           xmin: 1 ymin: 1 xmax: 1 ymax: 1
CRS:            NA

Some of this behaviour might be different on newer versions of GDAL with newer versions of PROJ - lots of CRS handling has changed.

1
  • I think I made a mistake transcribing this to stackexchange. My original code does have a leading plus sign and still generates the error ``` crs(cropscape) <- "+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0" Warning message: In .newCRS(value) : +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0 is not a valid PROJ.4 CRS string – user168982 Aug 23 '20 at 21:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.