Friday, June 25, 2010

Howto export points to a Google Earth KML file

The problem:
A table of xyz data points can be viewed spatially with different methods:
GMT and ArcView are just a couple of options. I often get tables of spatial data points in Microsoft Excel (xp ver.) format or CSV of some kind. An easy (and free) way to visualize the data points on Windows would be to export the data and view it on Google Earth.
The solution:
points2kml (115kb).
In order to ease the work-flow I wrote a VBA macro add-in for Excel that exports selected fields (longitude, latitude, name and data) to a Google Earth KML file. the point2kml add-in and can be found on my scripts page.

Wednesday, June 2, 2010

How to format a hard drive on Linux

The Problem:
How to format a hard drive on Linux.

The Solution:
in order to format a HD on Linux you'll need super user privileges.
you can use sudo if you have sudo privilages or in the terminal
switch to super user:

>su
(give super user pwd)
and ignore the sudo in the following commands. if you're system can't find the commands while in su mode, try to add /sbin/ before the command.
follow the steps below: marked with •
run commnads marked with >
commands output looks like this.
Warning: formatting your HD will erase all data on it!
  • Connect the HD to the computer, make sure it's on. 
  • get the hard drive's (device) name on your system:
>df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_insarlablin-lv_root
                      908G   77G  786G   9% /
/dev/sda1             194M   31M  153M  17% /boot
/dev/sdb1             1.4T  1.1T  193G  86% /home/novitsky
/dev/sdc1             1.4T  1.1T  193G  86% /home/novitsky/data

Now lets say our HD is sdb1.
  • lets build it's partition:
>sudo fdisk /dev/sdb
The number of cylinders for this disk is set to 182401.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)


Command (m for help): 
  • pressing m will get this menu:

Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

  • pressing p will print the current partition:

Disk /dev/sdb: 1500.3 GB, 1500301910016 bytes
255 heads, 63 sectors/track, 182401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000923e6

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1      182401  1465136001   83  Linux

  • pressing d will delete the current partition. depending on the partition you want to delete (this case 1) press the number of the partition to be deleted. if all the disk should be formatted and there are several partitions repeat pressing d and the number of the partitions until you delete them all.
  • pressing n will create a new partition.
  • pressing p will create a primary partition. select 1 as the number of the partition. use the defaults (just press Enter) for the start and end cylinders.
  • pressing t will set the file system type.
  • pressing l will list the available file systems.
  • select 83 if you want a Linux file system
  • pressing w will write and exit to shell.
Now we will create a new file system on the new partition:
> sudo mkfs -t ext2 /dev/hdb1
remember to change the number at the end if your HD device number is different.
if your using different fs than ext2 (newer Linux systems have ext3 and fc11 has ext4) replace the ext2 in the command with the correct fc name.
the mkfs may take some time to run (depending on the computer and HD size).

To add a label to the partition use:
e2label /dev/sdb1 NEWLABEL
where sdb should be changed to the correct device and NEWLABEL changed to the new label.

Now add the device to the fstab file in order to mount it:
> sudo vi /etc/fstab
and add a line like:
LABEL=NEWLABEL MOUNTPOINT ext3 defaults 1 2
where NEWLABEL is the disk labe and MOUNTPOINT is where you want to mount the disk.
mount it using:
> sudo mount -a
Note you might need to change permissions and owner of the mount point:
> sudo chown username:usergroop MOUNTPOINT
when finnished - reboot.