how to create a georefernce matrix from 2d lat and lon matrix

How can I create a GeoTIFF file from a 2d matrix of latitude and a 2D matrix of longitude and a 2d matrix of data like temperature? I need to combine the lat long and data to create a GeoTIFF file. The purpose is to create a temp file with each pixel representing lat-long and temperature.

[Sachin Kumar]

Check below link: https://in.mathworks.com/matlabcentral/answers/101643-how-can-i-use-the-mapping-toolbox-2-7-2-r2009a-to-map-a-specific-region-of-pixels-to-lat-lon-coord?s_tid=answers_rc1-3_p3_Topic

Answer 1

[Andreas Westergaard]

I have tried to find a solution to this, but have yet to find a way in Matlab. The example from KSSV seems to work nicely if you have 1D arrays with lat lon coordinates which can be converted to an evenly spaced grid. However, for the problem OP refer to with a 2D lat lon which may not be evenly spaced or aligned within meridians it may not work/give a wrong georeference.

If you have a matrix "lat" and matrix "lon" and matrix "data" in a WGS84 coordinate system, then the function

geoshow(lat,lon,data,'DisplayType', 'surface');

seems to work to plot the data as a map. The problem from there is to export the map as e.g. a geotiff.

So any ideas on either exporting the map from the geoshow-figure or creating a reference matrix "R" from a 2D lat, 2D lon, 2D data input would be fantastic!?

[kinga kulesza]

Did anyone found a solution? I'm facing the same problem now...

[rajasweta datta]

I geoerenced the lat long data using a library in R. There is another way of going about it convert 2D lat lon file to 1D array and export lat long to a csv file. Read csv file in arc GIS and create point file and then convert the point file using point to raster tool. add the resolution, for values use any random number depending on size of your arster. you can later change the values depending on you original file when you import the dummy raster on MATLAb as a 2D matrix.

[kinga kulesza]

I know it is a Matlab forum, but could you share a brief description how to do it in R, or just a name of a function/ tool that you used in R to georeference lats and lons? That would be very helpful for me. Thanks!

[rajasweta datta]

please try this link

https://rdrr.io/github/environmentalinformatics-marburg/Rsenal/man/rasterizeRegCM.html

the function coverts 2d matrix of lat, lon and data into a georeferenced dataset, helpful for model outputs.

all 3 values can be csv files, 2 for lat and long and other for data

code for example

lon <- raster(as.matrix(read.csv(paste0(basefolder,"lon.csv"),header=FALSE)))

lat <- raster(as.matrix(read.csv(paste0(basefolder,"lat.csv"),header=FALSE)))

x <- raster(as.matrix(read.csv(file,header=FALSE)))

result <- rasterizeRegCM(x,lat,lon)

writeRaster(result,paste0(substr(file,1,nchar(file)-4),".tif"))

[Natalia]

Hello, rajasweta datta

i was wondering if can i ask you for help to solve this? I am facing the same problem but in my case i have sometimes matrices with 2D dimensions, let's say ccaug=111x74 where 111 is longitude and 74 latitude, also my lat=111x74 and lon=111x74 and i have another matrix ccyraug=111x74x30, where 30 is my time (30 years), so in this case i have values within my domain 111x74. Should i use the same approach ? convert my matrices to .cvs and how can i convert each of the 30 years? and then how can i use the function you provided in R to apply it to my 30 years matrix? I've never used R before so it may be a bit tricky for me to use it for the first time.

Thanks in advance

Answer 2

[KSSV]

Let x, y be your vectors of longitude,latitude respectively. And data be your temperature matrix.

 xmin = min(x) ; xmax = max(x) ;
 ymin = min(y) ; ymax = max(y) ;
 R = georasterref('RasterSize',size(data),'LatitudeLimits',[ymin,ymax],'LongitudeLimits',[xmin,xmax]);
  geotiffwrite('myfile.tif',data,R)   % write data to .tif file
  %%Read geotiff file
  [A, R] = geotiffread(tiffile);
  figure
  mapshow(A, R);
  axis image off

[Hamidreza Norouzi]

But she asked when x and y are two 2-D matrices, not vectors. I have the same question.

[rajasweta datta]

Hi ,

I got the solution but I actually had take help of R for this, if you still have the problem I might be able to help.

regards

Raj