Downloading the SRTM V3.0 using a PERL script

GeoTiff is the best format to download because it runs very well with GDAL and GRASS, the tiles are in 5º by 5º. I am interrested in area between 35ºE -> 100º E; 30ºN -> 60ºN, this is a huge square from the western med. till the middle of China. The main objective is only the Aral Sea, but since I need to catch all the NIS countries the area has to be relatively big (Kazakhstan is HUGE!!!)

From the map I need all the tiles from x=44 y=6 till x=56 y=1 (left bottom till rigth top) this gives a big amount of clicks/downloads !!!! Using the approach of lets spend 99% of the time making a script that will do 100% of the job in 1% of the time, I decided to make a simple PERL scrip.

I am no PERL expert, I normally program in C/C++ so I am not familiar with PERL, but it was relatively simple because I had a book around the house called "Perl for C programmers" and the code lines for the FTP access where more or less copied from the explanation of how the Net::FTP module works.

The tile files have a structure like srtm_X_Y.zip so the script asks for the minimal and maximal number for x and y, after it makes the URL string and opens an FTP connection to the italian server. The script only has the debug dumping of the FTP connection.

Just copy/paste the next files to a file and run it:

#!/usr/bin/perl
#The script generates the URL of the files to download
#then it opens an FTP connection a gets the file
#simple, clean without much programming advances and it works
#note: the file code is something like this srtm_X_Y.zip
use strict;
use warnings;
use Net::FTP;
#variable declaration
#specific varibles, change here according to needs
my $ftp_url="ftplmu.jrc.it";
my $ftp_pwd="/pub/SRTM_v3/SRTM_Data_GeoTiff";
my $ftp_file;
my $ftp;
#input variables
my $max_x;
my $min_x;
my $max_y;
my $min_y;
#other variables
my $temp_min_y;
my $formated_number_y;
my $formated_number_x;
my $file_url;
#user input
print "Enter tile number of maximum long. (x): ";
$max_x=<STDIN>;
chomp($max_x);
print "Enter tile number of minimum long. (x): ";
$min_x=<STDIN>;
chomp($min_x);
print "Enter tile number of maximum lat. (y): ";
$max_y=<STDIN>;
chomp($max_y);
print "Enter tile number of minimum lat. (y): ";
$min_y=<STDIN>;
chomp($min_y);
#for loop to generate the url and open the FTP connection
$temp_min_y=$min_y;
for ( ;$min_x<=$max_x; $min_x++) { #some nice C/C++ sytanx $formated_number_x=sprintf("%02d",$min_x); $min_y=$temp_min_y; for( ;$min_y<=$max_y; $min_y++) { $formated_number_y=sprintf("%02d",$min_y); $ftp_file="srtm_".$formated_number_x."_".$formated_number_y.".zip"; #creating the FTP object and getting the file $ftp = Net::FTP->new($ftp_url, Debug=>1, Passive=>1) or die "It is not connecting: $@";
$ftp->login("anonymous");
$ftp->cwd($ftp_pwd);
$ftp->message;
$ftp->binary;
$ftp->get($ftp_file) or die "Get failed ", $ftp->message;
$ftp->quit;
}
}