April 24th, 2012 (4 weeks ago)
Dexter
I needed to calculate the distance between to
GPS coordinates. I have found couple of methods.
1. Postgres earthdistance
you need to install the contrib package for postgres. Import the cube.sql and the earthdistance.sql. More about this at postgresql docs
psql -d yourdatabase -f cube.sql
psql -d yourdatabase -f earthdistance.sql
To test:
SELECT
(point (47.5047554664,19.0479136054) <@> point (47.5049898995,19.0469509363))
AS distance;
distance
--------------------
0.0682533383274021This is in statute miles. Simply multiple by 1.609344 to have it in km.
2. PostGIS 2.0
After installing and importing the required postgis.sql and spatial_ref_sys.sql
you will have a lot of nice support for geographic object in your database. read more on the PostGIS site. ST_distance_sphere is considered the most accurate function to calculate the distance between 2 GPS points result is in meters.
Here is the verdict:
SELECT
round(
CAST(
ST_Distance_Spheroid(
ST_GeomFromText('POINT(47.5047554664 19.0479136054)',4326),
ST_GeomFromText('POINT(47.5049898995 19.0469509363)',4326),
'SPHEROID["WGS 84",6378137,298.257223563]')
AS NUMERIC),4) AS spheroid,
round(
CAST(
ST_distance_sphere(
ST_GeomFromText('POINT(47.5047554664 19.0479136054)',4326),
ST_GeomFromText('POINT(47.5049898995 19.0469509363)',4326)
) AS NUMERIC),4)
AS sphere,
round(
CAST(
((point (47.5047554664,19.0479136054)
<@>
point (47.5049898995,19.0469509363)) * 1.609344)
AS NUMERIC) * 1000,4)
AS earthdistance;
spheroid | sphere | earthdistance
----------+----------+---------------
109.3804 | 109.8435 | 109.8431there is not much difference, now it will be question of performance.
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I was wondering if the
comment-dwin (M-;) command could be changed that if i am anywhere in the line the whole line is commented and not a
comment started from the end of the line. based on the idea found in a mailing list i altered the command with
;; http://www.opensubscriber.com/message/emacs-devel@gnu.org/10971693.html
(defun comment-dwim-line (&optional arg)
(interactive "*P")
(comment-normalize-vars)
(if (and (not (region-active-p)) (not (looking-at "[ \t]*$")))
(comment-or-uncomment-region (line-beginning-position) (line-end-position))
(comment-dwim arg)))
(global-set-key "\M-;" 'comment-dwim-line)add this to your .emacs file and enjoy.
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How to
install Emacs from source?
You will need Xcode tools to perform this operation.
MacBook-Pro: mkdir src
MacBook-Pro: cd src
MacBook-Pro: cvs -z3 -d:pserver:anonymous@cvs.sv.gnu.org:/sources/emacs co emacs
MacBook-Pro: cd emacs
MacBook-Pro: ./configure --with-ns --with-jpeg=no --with-gif=no --with-tiff=no
MacBook-Pro: make bootstrap
MacBook-Pro: make
MacBook-Pro: make install
MacBook-Pro: sudo cp -r nextstep/Emacs.app /Applications/Emacs.app
if you would like to use it in terminal
MacBook-Pro: cd src
MacBook-Pro: make
MacBook-Pro: cp emacs /usr/bin/emacs
MacBook-Pro: emacs --version
GNU Emacs 23.1.90.1
Copyright (C) 2009 Free Software Foundation, Inc.
GNU Emacs comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of Emacs
under the terms of the GNU General Public License.
For more information about these matters, see the file named COPYING
MacBook-Pro: emacs -nw
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open a terminal and run the following to show hidden files
MacBook-Pro: defaults write com.apple.Finder AppleShowAllFiles true
MacBook-Pro: killall Finder
to hide them run the following
MacBook-Pro: defaults write com.apple.Finder AppleShowAllFiles false
MacBook-Pro: killall Finder
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I have my MacBookPro for 1 year now, and recently I had to often the message that my
MAC OS X HDD is running out of space, and effectively finder said ZeroKB, df -h 0 available. As I was installing quite a lot of apps for test during the last year, I have decided to reinstall
snow leopard.
Read more…
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Unfortunately my
previous solution was only temporary, after a while I mentioned that mongrels are eating the memory and hanging.
Read more…
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I have seen some serious performance issues and some error messages with
nginx and
mongrel_
cluster.
Read more…
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