CODEWITHSUNDEEP
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Kanwal Nayan
Kanwal Nayan

Reputation: 71

How can i read MTL file in R

I am very much new to R programming kindly someone tell how can i read the MTL file which is archived with landsat satellite data.

Upvotes: 3

Views: 1685

Answers (3)

morteza
morteza

Reputation: 303

for reading Mtl file along with your images (stack image) you can do the following:

  1. Give the directory of you Mtl file. For example

    mtlFile<- "\\LE07_L1TP_165035_20090803_20161220_01_T1_MTL.txt"

  2. Read metadata

      metaData <- readMeta(mtlFile)
  metaData

  3. Load rasters based on the metadata file

     lsat <- (stackMeta(mtlFile, quantity = "all", category = "image", 
 + allResolutions = FALSE))
 lsat
 plot(lsat)

Upvotes: 0

Paulo E. Cardoso
Paulo E. Cardoso

Reputation: 5856

For standard MTL file provided with Landsat scenes obtained from EarthExplorer or Glovis sevices, you could simply do:

mtl <- read.delim('L71181068_06820100518_MTL.txt', sep = '=', stringsAsFactors = F)

So, for something starting like this:

GROUP = L1_METADATA_FILE  GROUP = METADATA_FILE_INFO...

You may use this:

> mtl[grep("LMAX",mtl$GROUP),]
                  GROUP L1_METADATA_FILE
64          LMAX_BAND1           293.700
66          LMAX_BAND2           300.900
68          LMAX_BAND3           234.400
70          LMAX_BAND4           241.100
72          LMAX_BAND5            47.570
74         LMAX_BAND61            17.040
76         LMAX_BAND62            12.650
78          LMAX_BAND7            16.540
80          LMAX_BAND8           243.100
84       QCALMAX_BAND1             255.0
86       QCALMAX_BAND2             255.0
88       QCALMAX_BAND3             255.0
90       QCALMAX_BAND4             255.0
92       QCALMAX_BAND5             255.0
94      QCALMAX_BAND61             255.0
96      QCALMAX_BAND62             255.0
98       QCALMAX_BAND7             255.0
100      QCALMAX_BAND8             255.0

There are dictionaries provided by each service, found here and here.

Information from MTL may be critical for applying atmospheric and radiometric correction. By the way, landsat package allows you to run some of more typical correction using DOS() and radiocorr() functions.

You will also need standard calibration values provided by Chander et al. (2009).

For more complex approaches this may be a good start.

Upvotes: 3

Carl Witthoft
Carl Witthoft

Reputation: 21502

The MTL file contains only metadata (I hope you knew that :-)) and is a plain text file, so you could just read it in and parse as desired. If you are reasonably familiar with Matlab, you could port this tool http://www.mathworks.com/matlabcentral/fileexchange/39073 , converting it into R code.

EDIT: I can't tell from your comments what you actually need. Here's an example MTL.txt file I pulled off the net: http://landsat.usgs.gov/images/squares/processing_level_of_the_Landsat_scene_I_have_downloaded1.jpg

If you look at it, you can see the names and values of the data items. If those are what you want, perhaps the easiest way to get them would be to run the command

mtl.values <- read.table('filename.txt' , sep='=')

Which will give you a 2-column dataframe, with names in first column and values in the second.

Upvotes: 1

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