Geographic Information Systems Asked by ktop on December 17, 2020
I’m working on a project where I must use the map: Corine land cover.
https://land.copernicus.eu/pan-european/corine-land-cover/clc2018
(You can download the map in the .tif format)
I’m not familiar with gdal and rasters and I’m using Python to get the data out of the raster. I’m so confused?
Coordinate System is:
PROJCRS["ETRS_1989_LAEA",
BASEGEOGCRS["ETRS89",
DATUM["European Terrestrial Reference System 1989",
ELLIPSOID["GRS 1980",6378137,298.257222101004,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4258]],
CONVERSION["Lambert Azimuthal Equal Area",
METHOD["Lambert Azimuthal Equal Area",
ID["EPSG",9820]],
PARAMETER["Latitude of natural origin",52,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",10,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["False easting",4321000,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",3210000,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["(E)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["(N)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
ID["EPSG",3035]]
Data axis to CRS axis mapping: 1,2
Origin = (900000.000000000000000,5500000.000000000000000)
Pixel Size = (100.000000000000000,-100.000000000000000)
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
COMPRESSION=LZW
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 900000.000, 5500000.000) ( 56d30'18.51"W, 56d29' 4.75"N)
Lower Left ( 900000.000, 900000.000) ( 23d49'33.58"W, 24d17' 3.04"N)
Upper Right ( 7400000.000, 5500000.000) ( 72d54'22.09"E, 58d57' 9.90"N)
Lower Right ( 7400000.000, 900000.000) ( 40d39'45.75"E, 25d32'40.96"N)
Center ( 4150000.000, 3200000.000) ( 7d30'57.52"E, 51d53' 2.21"N)
Band 1 Block=65000x1 Type=Int16, ColorInterp=Gray
Min=111.000 Max=999.000 Computed Min/Max=111.000,999.000
Minimum=111.000, Maximum=999.000, Mean=326.518, StdDev=118.029
NoData Value=-32768
Metadata:
DESCRIPTION=clc18
RepresentationType=THEMATIC
STATISTICS_MAXIMUM=999
STATISTICS_MEAN=326.51842078382
STATISTICS_MINIMUM=111
STATISTICS_SKIPFACTORX=1
STATISTICS_SKIPFACTORY=1
STATISTICS_STDDEV=118.02878635921
STATISTICS_VALID_PERCENT=24.58
import gdal
import numpy
from affine import Affine
lons=[15.174866]
lats=[43.169129]
fn="C:/path-to-the-map/map.tif"
ds=gdal.Open(fn)
transform=ds.GetGeoTransform()
xOrigin=transform[0]
yOrigin=transform[3]
pixelWidth=transform[1]
pixelHeight=transform[5]
aff=Affine.from_gdal(xOrigin,pixelWidth,0.0,yOrigin,0.0,pixelHeight)
x_coords,y_coords=aff*(numpy.array(lons),numpy.array(lats))
band=ds.GetRasterBand(1).ReadAsArray()
x=int(x_coords[0]/pixelWidth)
y=int(y_coords[0]/pixelHeight)
value=band[x][y]
print(value)
I get some value from the raster but the value is not correct.
My guess is that I am not converting the coordinates in the right way. I need to convert the coordinates 43.169129 lat, 15.174866 lon to coordinates used in the map to extract data at that exact spot.
You can use rioxarray for this:
import rioxarray
from pyproj import Transformer
# convert coordinate to raster projection
lon = 15.174866
lat = 43.169129
rds = rioxarray.open_rasterio("C:/path-to-the-map/map.tif")
transformer = Transformer.from_crs("EPSG:4326", rds.rio.crs, always_xy=True)
xx, yy = transformer.transform(lon, lat)
# get value from grid
value = rds.sel(x=xx, y=yy, method="nearest").values
You can also do this with rasterio
:
import rasterio
from pyproj import Transformer
lon = 15.174866
lat = 43.169129
with rasterio.open("C:/path-to-the-map/map.tif") as rds:
# convert coordinate to raster projection
transformer = Transformer.from_crs("EPSG:4326", rds.crs, always_xy=True)
xx, yy = transformer.transform(lon, lat)
# get value from grid
value = list(rds.sample([(xx, yy)]))[0]
Correct answer by snowman2 on December 17, 2020
Similarly, you can use gdallocationinfo
from the command line. E.g.
if you have your coordinates in a text file called coords.xy
, you can just type
cat coords.xy | gdallocationinfo -wgs84 -valonly map.tif > values.xy
and your outputs are in file values.xy
(same order as coords.xy
). Blindingly fast! See here for details
Answered by Jose on December 17, 2020
If your expected output is just convert raster information to text, you can try gdal2xyz.py
$ python gdal2xyz.py -csv input.tif output.csv
Then you will get a csv file with XYZ information: Longitude, Latitude, and Raster information (land use)
Answered by user97103 on December 17, 2020
Get help from others!
Recent Answers
Recent Questions
© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP