iphone and gis development notes » GIS

Postgres PostGIS CheatSheet v2

rupert — Fri, 29 Aug 2008 05:10:32 +0000

This is a quick-command list of Postres. If you want detailed instructions, please visit the Postgres Manual.

How do I Show all databases?
1. Using “psql -l”

2. Using

postgres=# \l
List of databases
Name       |  Owner   | Encoding
------------------+----------+----------
postgis          | postgres | UTF8
postgres         | postgres | UTF8
template0        | postgres | UTF8
template1        | postgres | UTF8
template_postgis | postgres | UTF8
(5 rows)

Note: Do not drop template databases if not necessary.

How do I run a script from the prompt?
psql -d cybersoftbj -u user -f myfile.sql

Its very useful in reloading user-defined functions.

How do I create a user/role?
CREATE ROLE lbs WITH LOGIN PASSWORD 'mypassword' SUPERUSER INHERIT CREATEDB CREATEROLE;

How do I change the password for a user/role?
ALTER ROLE lbs PASSWORD 'mynewpassword';

How to provide/restrict access privileges to tables?
GRANT SELECT ON TABLE table TO user; REVOKE SELECT ON TABLE table FROM user;

How to dump database in a text file?
pg_dump -U lbs -d cybersoftbjv1 -h 127.0.0.1 -W > cybersoftbjv1.sql

How to dump database cleanly?
pg_dump -c -d -E UTF8 -h 127.0.0.1 -U lbs -W platform_v1 > platform_v1.sql

How to rename a database?
ALTER DATABASE beijing_app RENAME TO beijing_app_20080801;

How to update using two tables?
UPDATE road_for_update u SET the_geom = r.the_geom FROM roads r WHERE r.rd_id = u.rd_id;

How to change a column type with Cast?
ALTER TABLE roads ALTER COLUMN class_new TYPE integer USING class_new::integer;

How to add a geometry column to a table?
EXAMPLE: SELECT AddGeometryColumn(‘public’, ‘poi’, ‘the_geom’, 4326, ‘POINT’, 2)

Changing column names with spaces?
ALTER TABLE class_aroundme RENAME "level 1" TO level_1;

Setting kernel shmmax for postgres
sysctl -w kernel.shmmax=134217728
Note: For permanent changes see /etc/sysctl.cfg11. How to backup table(s) from pg_dump?
pg_dump poi_beijing -t class -t poi_class -f $BACKUPDIR/test_$MYDATE.sql

Using GDALWARP to reproject raster that will fit with Google Satellite

rupert — Tue, 29 Jul 2008 12:48:21 +0000

Just a couple of notes to onself using gdal: Use gdalwarp to reproject your GeoTIFF files! I wanted to use my own satellite images acquired from GeoEye, however, on some areas I wanted to use google sat images as well since I don’t have the coverage. In order to do so, I need to reproject the sat images to 900913. Note you need to specify this in your epsg file in my previous post.

rupert:beijing_900913_satellite rupert$ gdalinfo Mosaic_RGB.tif
Driver: GTiff/GeoTIFF
Files: Mosaic_RGB.tif
Size is 4248, 4553
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.2572235630016,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (116.291476140000000,40.025198500000002)
Pixel Size = (0.000046860000000,-0.000035970000000)
Metadata:
  AREA_OR_POINT=Area
  TIFFTAG_XRESOLUTION=100
  TIFFTAG_YRESOLUTION=100
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  ( 116.2914761,  40.0251985) (116d17'29.31"E, 40d 1'30.71"N)
Lower Left  ( 116.2914761,  39.8614271) (116d17'29.31"E, 39d51'41.14"N)
Upper Right ( 116.4905374,  40.0251985) (116d29'25.93"E, 40d 1'30.71"N)
Lower Right ( 116.4905374,  39.8614271) (116d29'25.93"E, 39d51'41.14"N)
Center      ( 116.3910068,  39.9433128) (116d23'27.62"E, 39d56'35.93"N)
Band 1 Block=4248x1 Type=Byte, ColorInterp=Red
Band 2 Block=4248x1 Type=Byte, ColorInterp=Green
Band 3 Block=4248x1 Type=Byte, ColorInterp=Blue

rupert:beijing_900913_satellite rupert$ gdalwarp -s_srs epsg:4326 -t_srs epsg:900913 Mosaic_RGB.tif sat_4m_rgb.tif
Creating output file that is 4245P x 4556L.
Processing input file Mosaic_RGB.tif.
0...10...20...30...40...50...60...70...80...90...100 - done.

rupert:beijing_900913_satellite rupert$ gdalinfo sat_4m_rgb.tif
Driver: GTiff/GeoTIFF
Files: sat_4m_rgb.tif
Size is 4245, 4556
Coordinate System is:
PROJCS["Google Maps Global Mercator",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.2572235630016,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Mercator_1SP"],
    PARAMETER["central_meridian",0],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]
Origin = (12945507.907502911984921,4869604.732793668285012)
Pixel Size = (5.219801430503303,-5.219801430503303)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (12945507.908, 4869604.733) (116d17'29.31"E, 40d12'53.10"N)
Lower Left  (12945507.908, 4845823.317) (116d17'29.31"E, 40d 3'2.78"N)
Upper Right (12967665.965, 4869604.733) (116d29'25.89"E, 40d12'53.10"N)
Lower Right (12967665.965, 4845823.317) (116d29'25.89"E, 40d 3'2.78"N)
Center      (12956586.936, 4857714.025) (116d23'27.60"E, 40d 7'58.12"N)
Band 1 Block=4245x1 Type=Byte, ColorInterp=Red
Band 2 Block=4245x1 Type=Byte, ColorInterp=Green
Band 3 Block=4245x1 Type=Byte, ColorInterp=Blue

Installing Mapserver on MacOSX (by source)

rupert — Sat, 26 Jul 2008 04:03:16 +0000

Just noticed that William of kyngchaos has updated the mapserver binary for MacOSX.

But right now, I need to tile these images bought from GeoEye, so I need TIFF support. Below is a summary of getting Mapserver installed by source. Note that I have the necessary GEOS, GDAL from kyngchaos as well from this ealier post.

1. Download the ff files:
-rw-r--r--@ 1 rupert admin 564313 Jul 26 10:32 agg-2.5.tar.gz -rw-r--r--@ 1 rupert admin 1345700 Jul 26 10:22 gd-2.0.35.tar.gz -rw-r--r--@ 1 rupert admin 613261 Jul 26 10:22 jpegsrc.v6b.tar.gz -rw-r--r--@ 1 rupert admin 796551 Jul 26 10:22 libpng-1.2.29.tar.gz -rw-r--r--@ 1 rupert admin 1948751 Jul 26 09:55 mapserver-5.2.0.tar.gz -rw-r--r--@ 1 rupert admin 1336295 Jul 26 11:11 tiff-3.8.2.tar.gz

2. Install in the ff order:

- jpegsrc
- libpng
- gd (if you have trouble installing gd, then follow this pdf:installing_gd2_on_os_x_server)
- agg (make only)
- tiff
- mapserver

3. For mapserver, please install using the ff configure switches:

./configure \
--with-agg=/myhome/rupert/mapserver/agg-2.5 \
--with-jpeg \
--with-gd \
--with-freetype \
--with-png \
--with-ogr \
--with-proj \
--with-gd \
--with-httpd=/usr/local/apache2/bin/httpd \
--with-tiff \
--with-wfs \
--with-wcs \
--with-sos \
--with-wmsclient \
--with-wfsclient \
--with-tiff \
--with-gdal=/usr/local/bin/gdal/gdal-config \
--with-geos=/usr/local/bin/geos-config \
--with-postgis=/usr/local/pgsql/bin/pg_config

4. Mapserver output

rupert:mapserver-5.2.0 rupert$ ./mapserv -v
MapServer version 5.2.0 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP OUTPUT=SVG SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=ICONV SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT SUPPORTS=WCS_SERVER SUPPORTS=SOS_SERVER SUPPORTS=GEOS INPUT=TIFF INPUT=EPPL7 INPUT=POSTGIS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE

Postgres PostGis PostInstall

rupert — Fri, 06 Jun 2008 23:34:36 +0000

1. Edit pg_hba.conf

# "local" is for Unix domain socket connections only
local   all         all                               trust
# IPv4 local connections:
host    all         all         127.0.0.1/32          md5
host    all         all         192.168.1.0 255.255.255.0       md5
# IPv6 local connections:
#host    all         all         ::1/128               trust

2. Edit postgres.conf

55
56 listen_addresses = '*' # what IP address(es) to listen on;
57 # comma-separated list of addresses;
58 # defaults to 'localhost', '*' = all
59 # (change requires restart)

4. For CentOS5.1, create symbolic links:
ln -s /usr/local/lib/libproj.so.0 /usr/lib/libproj.so.0
ln -s /usr/local/lib/libgeos_c.so.1 /usr/lib/libgeos_c.so.1
ldconfig
/etc/init.d/postgresql stop
/etc/init.d/postgresql start

3. Postgis Post Install

createdb -E utf8 template_routing
createlang plpgsql template_routing
psql -d template_routing -f /usr/share/postgresql-8.3-postgis/lwpostgis.sql 
psql -d template_routing -f /usr/share/postgresql-8.3-postgis/spatial_ref_sys.sql 
psql -d template_routing -f /usr/share/postlbs/routing_core.sql 
psql -d template_routing -f /usr/share/postlbs/routing_core_wrappers.sql

Installing Postgresql, Postgis, pgRouting on Debian

rupert — Sun, 25 May 2008 03:55:57 +0000

Operating System: Debian sid

Versions:

postgres 8.3.1
postgis 1.3.3
pgRouting1.02

1. Install base system and ssh

#vi /etc/apt/sources.list to include
deb http://debian.cn99.com/debian etch main
deb-src http://debian.cn99.com/debian etch main
#apt-get update
#apt-get upgrade libc6

2. Install the required packages for postgres8.3 and postgis1.3.3

#apt-get install sudo nmap telnet
#apt-get install python2.5 python2.5-dev python-setuptools
#apt-get install g++
#apt-get install build-essential cmake ibboost-graph-dev
#apt-get install libreadline5 libreadline5-dev
#apt-get install zlib-bin zlib1g-dev
#apt-get install libkrb5-dev
#apt-get install libcurl3
#apt-get install libssl-dev
#apt-get install postgresql-8.3
#apt-get install postgresql-8.3-postgis
#apt-get install postgresql-server-dev-8.3

3. Installing pgRouting

# tar -zxvf pgRouting-1.02.tgz
# cmake .
# make 
# make install

Jpeg decoder problem on TileCache on MacOSX Leopard

rupert — Mon, 12 May 2008 09:26:07 +0000

There is a problem with a “jpeg decoder” because Python Imaging Library (PIL) cannot find the jpeg libraries. Remember that we installed kyngchaos UnixIO libraries, therefore the PIL setup.py script should point to use those libraries.

Actually, I even installed the jpegsrc manually. I believe there is no need to do this, since UnixIO Image libraries is sufficient enough for PIL to install. What is important is to ensure that python tests succeeded. Once you get passed that, then installing PIL should work.

1. Extract Imaging-1.1.6.tar.gz
2. Edit setup.py to reflect:
JPEG_ROOT="/Library/Frameworks/UnixImageIO.framework/unix"
3. python setup.py build_ext -i
4. If no test fails, then go ahead and install
5. python setup.py install

Installing Mapserver on MacOSX Leopard (the easy way)

rupert — Tue, 06 May 2008 13:01:09 +0000

The easiest way to install mapserver on your Leopard is by downloading and installing dmg files from www.kyngchaos.com (courtesy of William Kyngesburye). These binaries were also noted from Mapserver’s Download Page.

1. Download the ff binaries in order (please note the version numbers at the time of writing):

1. UnixImageIO_Framework-1.0.22a.dmg
2. FreeType_Framework-2.3.5-3.dmg
3. GEOS_Framework-3.0.0-2.dmg
4. PROJ_Framework-4.6.0-1.dmg
5. SQLite3_Framework-3.5.7-1.dmg
6. MapServer-5.0.2-2.dmg

2. Once installed, you can copy the mapserv binaries to your apache cgi-bin

sudo cp /Library/WebServer/CGI-Executables/mapserv /usr/local/apache2/cgi-bin/

3. Check the mapserv output

rupert:~ rupert$ /usr/local/apache2/cgi-bin/mapserv -v
MapServer version 5.0.2 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP OUTPUT=SWF OUTPUT=SVG SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT SUPPORTS=WCS_SERVER SUPPORTS=SOS_SERVER SUPPORTS=FASTCGI SUPPORTS=GEOS INPUT=EPPL7 INPUT=POSTGIS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE

This is actually the first time I was able to install mapserver NOT BY SOURCE and still achieve the same binaries that I wanted (with AGG support). Full credit should be given to William.

Interesting Location Technologies

rupert — Fri, 25 Apr 2008 02:32:46 +0000

Been very busy for the past few days/weeks in the office. Just read this one from Google Reader, Nokia develops navigating system based on image recognition, landmarks. In summary, base from Nokia’s Palo Alto Research center, providing direction guiding varies from gender and culture. However, providing examples such as “Turn Right after the next gas station” seems to be a universal and a normal behavior of providing directions, the person can relate more to the advice than providing line routes above synthetic maps.

This is interesting facts as it supports our theory in Call Center Directed Guiding. Although, a 360 or panoramic view of any point along the line would be ideal, an easier and more realistic approach for the time being would be to include important landmark snapshots along the route. However, I believe our organisation’s project is one step ahead since we have a warm body who already gave a summary of the route during the conversation. This means the caller have an idea of the route complexity beforehand. Then, we could also send this landmark images to the subscriber’s mobile as his future reference (which means additional VAS).

Another interesting location technology, fruitful for direction guiding, would be iPointer. I believe, base on the coordinates and orientation, the server could algorithmically predict which POI you are looking at or infront of. They mentioned they have a thin client on the mobile device, so I guess the S60 client tries to get the orientation base on the bearing. Also check this one out, “users can now walk down the street anywhere in Japan and point at over 700,000 objects such as buildings, shops, restaurants, banks, historical sites and instantly retrieve information on what they are looking at or find what they are looking for just by pointing their phone.”. Niche eh? Just compells me more to start up our mobile pursuit…

But what rocked me the most was indoor tracking by Ubisense using ultrawideband technology which is close to a foot?!?. This I have to see, as it opens new business cases for direction guiding indoors such as big malls, etc. Imagine mapjack views inside malls with Ubisense technology. Sweet.

Other References:
http://www.openlandmark.com/

Using TileCache, OpenLayers, Mapserver for Projection 900913

rupert — Tue, 08 Apr 2008 01:50:12 +0000

I had a few problems with TileCache the other week which I am eager to blog about, since I knew for sure that later on, I might encounter the same. I don’t have the exact errors with me right now, so I’m jotting this down from my head…

Classic Resolutions problem. Use extent_type=loose
Can not set image type

UPDATED (JAN 11, 2010): Classic Resolutions problem:

How are resolutions calculated? Assuming we have:

Original:
Lower Left (LL) or minx, miny: 12453557, -5434940
Upper Right (UR) or max, maxy: 16980842, -1180729

maxResolution = (max – minx)/tilesize = (16980842 – 12453557)/512 = 8842.353
where tilesize = 512.

Therefore, we can set/guess for max so that we have maxResolution as a whole number.

Adjusted:
minx, miny: 12453557, -5434940
maxx, maxy: 16980661, -1180729

gives a maxResolution (whole number) of 8842.

Now, you can use 8842 in both the TileCache.cfg and OpenLayers Javascript.
A. Google BaseLayer + Road WMS Overlay = Validation approach before we proceed to TC.

1. OpenLayers (OL) Code: http://www.gisnotes.com/platform/docs/examples/GoogleWMSRoads.cfm

2. Map File Configuration: /home/map/beijing/new/beijing_google_roads

Well the above files are not exactly for TC, but it is a good demonstration that we could overlay our custom layers (WMS) on top of Google as the base layer. For a more detailed explanation regarding Google + OL, please read my previous gisnote. Also, this is a good test to see if our Mapserver mapfile configuration is correct. I do suggest not to proceed with OL + TC not unless you have validated the mapfile through OL (Google + WMS).

B. Google900913 Tilecache as baselayer

Ok.. so here it is..

1. OpenLayers Code: http://www.gisnotes.com/platform/docs/examples/TilecacheGoogle900913Base.cfm

        window.onload = function() {
            var options = {
                        projection: new OpenLayers.Projection("EPSG:900913"),
                        units: "m",
 
                        //maxResolution: 156543.0339,
                        resolutions : [156543.03390000001, 78271.516950000005, 39135.758475000002, 19567.879237500001, 9783.9396187500006, 4891.9698093750003, 2445.9849046875001, 1222.9924523437501, 611.49622617187504, 305.74811308593752, 152.87405654296876, 76.43702827148438, 38.21851413574219, 19.109257067871095, 9.5546285339355475, 4.7773142669677737, 2.3886571334838869, 1.1943285667419434, 0.59716428337097172, 0.29858214168548586],
                        //zoom: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19] @ numZoomLevels: 20
                        numZoomLevels: 20,
                        //maxExtent: new OpenLayers.Bounds(12823075.86334, 4800551.12375, 13101918.14248, 5021301.26141)
                        //maxExtent: new OpenLayers.Bounds(12823075, 4800551, 13101918, 5021301)
                        //maxExtent: new OpenLayers.Bounds(12848138, 4785083, 13080212, 5021118.5)
                        maxExtent: new OpenLayers.Bounds(-20037508, -20037508,20037508, 20037508.34)
                    };
 
            OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
            OpenLayers.Util.onImageLoadErrorColor = "transparent";
 
            map = new OpenLayers.Map('mapdiv',options);
 
            var serverURL = "/tilecache/tilecache.py";
            // start custom layer here
            var layer_obj = new OpenLayers.Layer.WMS(
                "Beijing",
                serverURL,
                {
                    layers: 'beijing_900913',
                    map: '/home/map/beijing/new/beijing_900913/beijing.map',
                    format: 'image/jpg',
                    'transparent': 'off'
                }
            );
            layer_obj.setIsBaseLayer(true);
            layer_obj.setVisibility(true);
            map.addLayer(layer_obj);

2. TileCache Configuration: /wwwroot/tilecache/tilecache.cfg

[beijing_900913]
type=WMSLayer
url=http://127.0.0.1/cgi-bin/mapserv?map=/home/map/beijing/new/beijing_900913/beijing.map
layers=beijing_900913
metatile=true
extension=jpg
levels=20
resolutions=156543.03390000001, 78271.516950000005, 39135.758475000002, 19567.879237500001, 9783.9396187500006, 4891.9698093750003, 2445.9849046875001, 1222.9924523437501, 611.49622617187504, 305.74811308593752, 152.87405654296876, 76.43702827148438, 38.21851413574219, 19.109257067871095, 9.5546285339355475, 4.7773142669677737, 2.3886571334838869, 1.1943285667419434, 0.59716428337097172, 0.29858214168548586
srs=EPSG:900913
bbox=-20037508, -20037508, 20037508, 20037508.34
#maxResolution=156543.0339
extent_type=loose
debug=on

You can either set resolutions or maxResolutions. I always wanted to be explicit, so setting the resolutions is my preference.

3. MapFile Configuration: /home/map/beijing/new/beijing_900913/beijing.map
I have a long mapfile, and using includes helped a lot, see my previous gisnote. For debugging your mapfile, read this post.

Always Remember…I believe when they made TC, I presume they always tested on WGS84(lonlat), this means if you don’t set anything explicit, it would implicitly set settings in WGS84(lon/lat)…

Ensure that you have the vector data in the necessary projection, in my case it’s 900913.

Ensure that the resolutions from OL (B.1) is reflected in TC configuration (B.2).

Ensure that the maxextents from OL (B.1) is reflected in TC configuration (B.2) as bbox.

C. Still can’t get it running?

1. Narrow down the error.

2. tail -f /var/log/apache2/error.log and access.log is your bestfriend. It’s a good starting point to trace down what went wrong. If you can’t see it from Apache’s error.log then ensure that python debugging is turned on.

3. Sometimes TC [a] gives you an obvious error or [b] its just a link to the mapserv request.

Examples of [a]:

Classic Resolution problem stated above. - If you followed my final notes above, then this should not happen. If you’ve set up things correctly but it’s still broken and you want to pull your hair out, then do a clean test stated below in D.
Cannot set image type – Check the extensions from the mapfile and TC config. Are they both in jpg’s?

The latter [b] is harder to debug. Most likely its a mapserver mapfile mishap and the easiest way to hunt this down is only thru your error.log (note: you need mapserver to have a debug=true when you compiled it, that’s another story.)

D. Doing a clean test as always
1. Always disable any caching when testing. Disable cache from your browser, for FF I use the webdeveloper toolbar. It’s as easy as Disable -> Disable Cache.

2. Stop/Start Apache. Hoping Python get’s a clean start as well. If you found any pyc (python compiled) under TC source directory… then stop Apache; remove the pycs; start Apache.

3. Seeing the same images? Always remove the image caches! rm -Rf /data/tilecache/beijing_900913

Installing Mapserver on Debian (reprise)

rupert — Fri, 28 Mar 2008 11:31:43 +0000

As noted from my previous blog post regarding Mapserver on Debian, you don’t get AGG with Mapserver when installing directly from Debian packages. Thus, it would be better to install Mapserver by source. However, debian still helps because it would install all the necessary libraries needed for compiling mapserver.

./configure \
--with-agg \
--with-jpeg \
--with-gd \
--with-freetype \
--with-png \
--with-ogr \
--with-proj \
--with-gdal \
--with-httpd=/usr/sbin/apache2 \
--with-tiff \
--with-wfs \
--with-wcs \
--with-threads \
--with-wmsclient \
--with-wfsclient \
--with-geos \
--with-postgis \
--enable-debug

When I started installing yesterday, I did not know which packages/libraries are installed in my box. I dove off immediately by running my configure.sh above and received an error: Could not find gd.h or libgd.a/libgd.so in /usr/local..

The best way to figure out if you’re ready is reading thru the configure output.

checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ANSI C... none needed
checking for g++... g++
checking whether we are using the GNU C++ compiler... yes
checking whether g++ accepts -g... yes
checking for ranlib... ranlib
checking for flex... no
checking for lex... no
checking for yywrap in -lfl... no
checking for yywrap in -ll... no
checking for bison... no
checking for byacc... no
checking if compiler supports -R... no
checking if compiler supports -Wl,-rpath,... yes
checking for exp in -lm... yes
checking for __gxx_personality_v0 in -lstdc++... yes
checking how to run the C preprocessor... gcc -E
checking for egrep... grep -E
checking for ANSI C header files... yes
checking for strcasecmp... yes
checking for strncasecmp... yes
checking for strdup... yes
checking for strlcat... no
checking for vsnprintf... yes
MapServer Version from mapserver.h: '5.0.2'
configure: checking where FreeType 2.x is installed...
checking for freetype-config... /usr/bin/freetype-config
using libfreetype from -lfreetype -lz
checking for FT_Init_FreeType in -lfreetype... yes
using libfreetype -lfreetype from system libs.
configure: checking where Zlib is installed...
checking for zlibVersion in -lz... yes
using libz from system libs (-DUSE_ZLIB).
configure: checking where PNG is installed...
checking for png_init_io in -lpng... yes
using libpng from system libs.
configure: checking whether we should include JPEG support...
checking for jpeg_read_header in -ljpeg... yes
using libjpeg from system libs.
configure: checking where libXpm is installed...
checking for XpmFreeXpmImage in -lXpm... yes
using libXpm from system libs.
configure: checking where libiconv is installed...
checking for iconv_open in -lc... yes
checking for libiconv_open in -liconv... no
using libiconv from system libs.
libiconv found. Enabling internationalization (-DUSE_ICONV)
configure: checking for GD 2.0.16 or higher...
checking for gdFontCacheSetup in -lgd... yes
using libgd 2.0.16 (or higher) from system libs (-L/usr/lib -lgd -ljpeg -lfreetype -lpng -lz -lXpm -lX11 ).
checking for gdImageCreate in -lgd... yes
checking for gdImageGif in -lgd... yes
checking for gdImagePng in -lgd... yes
checking for gdImageJpeg in -lgd... yes
checking for gdImageWBMP in -lgd... yes
checking for gdImageStringFT in -lgd... yes
checking for gdImageOpenPolygon in -lgd... yes
checking for gdImageGifPtr in -lgd... yes
checking for gdFontGetTiny in -lgd... yes
using GD ( -DUSE_GD_GIF -DUSE_GD_PNG -DUSE_GD_JPEG -DUSE_GD_WBMP -DUSE_GD_FT -DGD_HAS_FTEX_XSHOW -DGD_HAS_GDIMAGEGIFPTR -DGD_HAS_GETBITMAPFONTS) from system libs.
configure: checking whether we should include PDF support...
checking for PDF_setlinewidth in -lpdf... no
checking for PDF_setrgbcolor in -lpdf... no
checking for PDF_moveto in -lpdf... no
checking for PDF_curveto in -lpdf... no
checking for PDF_show_xy in -lpdf... no
checking for PDF_load_font in -lpdf... no
libpdf not found or too old... PDF support not included.
checking if AGG support requested... looking for agg libs in /usr
using libagg from /usr
using libaggfontfreetype from /usr
configure: checking whether we should include EPPL7 support...
including EPPL7 support.
configure: checking whether we should include PROJ.4 support...
checking for pj_init in -lproj... yes
checking for pj_transform in -lproj... yes
using PROJ.4 from system libs.
configure: checking whether we should include thread safe support...
checking for pthread_create in -lpthread... yes
using -lpthread from system libs.
configure: checking whether we should include ESRI SDE support...
ESRI SDE support not requested.
checking if GEOS support requested... yes
checking for geos-config... /usr/bin/geos-config
checking for GEOS version &gt;= 2.2.2... yes. Found version 2.2.3
configure: checking whether we should include OGR support...
checking for gdal-config... /usr/bin/gdal-config
OGR enabled (-DUSE_OGR).
checking if GDAL support requested... yes
checking checking ms JPEG output... no we, have GDAL available.
configure: checking whether we should include TIFF support...
checking for TIFFOpen in -ltiff... yes
using libtiff from system libs.
checking if PostGIS support requested... yes
checking for pg_config... /usr/bin/pg_config
yes, user supplied pg_config
checking if MyGIS support requested... no
checking if OracleSpatial support requested... no
checking if MING/Flash support requested... no
configure: checking whether we should include WMS Server support...
OGC WMS compatibility enabled (-DUSE_WMS_SVR).
configure: checking whether we should include WFS Server support...
OGC WFS Server support enabled (-DUSE_WFS_SVR).
configure: checking whether we should include WCS Server support...
OGC WCS Server support enabled (-DUSE_WCS_SVR).
configure: checking whether we should include WMS Client Connections support...
configure: checking whether we should include WFS Client Connections support...
configure: checking whether we should include OGC SOS Server support...
configure: checking for curl-config...
checking for curl-config... /usr/bin/curl-config
found libcurl version 7.18.0
OGC WMS Client Connections enabled (-DUSE_WMS_LYR).
OGC WFS Client Connections enabled (-DUSE_WFS_LYR).
configure: checking for xml2-config...
configure: checking whether FastCGI support should be enabled...
FastCGI support not enabled.
configure: checking HTTPD server (Apache) version...
using user-supplied httpd (/usr/sbin/apache2)
/usr/sbin/apache2 version is Apache/2.2.8 (2002008).
Your system is apparently running Apache/2.2.8. Setting stderr to non-blocking for msDebug() due to Apache 2.x bug (see MapServer bug 458 or Apache bug 22030).
Compiling with fast MS_NINT
checking compiler warnings... basic
configure: checking whether we should enable debug features...
Enabling debug features: -g in CFLAGS.
configure: checking for PHP/MapScript module options...
PHP/MapScript module not configured.
checking for g++ -shared ... yes
checking if --enable-runpath requested... no
checking if --with-java-include-os-name specified... no, autodetected linux
configure: creating ./config.status
config.status: creating Makefile
config.status: creating mapscript/java/Makefile
config.status: creating mapscript/csharp/Makefile
MapServer is now configured for
-------------- Compiler Info -------------
C compiler: gcc -g -O2 -fPIC -Wall
C++ compiler: g++ -g -O2 -fPIC -Wall
Debug: -g -DNEED_NONBLOCKING_STDERR
Generic NINT:
Threading support: -DUSE_THREAD
-------------- Renderer Settings ---------
zlib support: -DUSE_ZLIB
png support:
jpeg support:
iconv support: -DUSE_ICONV
AGG support: -DUSE_AGG
AGG Freetype support: -laggfontfreetype
Ming(flash) support:
PDFLib support:
-------------- Data Format Drivers -------
native tiff support: -DUSE_TIFF
PostGIS support: -DUSE_POSTGIS
Proj.4 support: -DUSE_PROJ
EPPL7 support: -DUSE_EPPL
ArcSDE support:
OGR support: -DUSE_OGR
GDAL support: -DUSE_GDAL
GEOS support: -DUSE_GEOS
Oracle Spatial support:
FastCGI support:
-------------- OGC Services --------------
WMS Server: -DUSE_WMS_SVR
WMS Client: -DUSE_WMS_LYR
WFS Server: -DUSE_WFS_SVR
WFS Client: -DUSE_WMS_LYR
WCS Server: -DUSE_WCS_SVR
SOS Server:
-------------- MapScript -----------------
PHP MapScript: no

I was able to weed out the problem above by checking on the libraries noted with “yes” above if they are installed or not. To overcome this, I needed to install the ff debian packages on ‘lenny(testing)’:

libagg-dev libgd2-xpm libgd2-xpm-dev libtiff4 libtiff4-dev libpng libpng-dev libxpm4 libxpm4-dev libfreetype6-dev libapache2-mod-python python-imaging

Results:

debsexy:/usr/lib/cgi-bin# ./mapserv -v
MapServer version 5.0.2 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP OUTPUT=SVG SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT SUPPORTS=WCS_SERVER SUPPORTS=THREADS SUPPORTS=GEOS INPUT=TIFF INPUT=EPPL7 INPUT=POSTGIS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE

Installing PostGres8.3 and Postgis1.3.2 on Windows

rupert — Tue, 04 Mar 2008 00:15:05 +0000

It seems very nice for the new PostGres8.3 installer to bundle up third party libraries installation with the new admin pack feature. Using this feature, you can install PostGis, nPgsql, etc. The installation was painless and smooth this time. I have to backup all my data though using pg_dump.

To lessen the learning curve on installing PostGres + PostGis together, I made a short flash movie here. There is no audio in the tutorial. The idea was to introduce PostGres to my Chinese staff. I have to remove PostGreSQL 8.2 first before installing 8.3.

Making GeoJSON outputs from PostGIS

rupert — Sat, 23 Feb 2008 02:08:17 +0000

I have an internet/web application sitting on top of OpenLayers, ExtJS, ColdFusion and PostGreSQL/PostGIS. I can query the geometry from PostGIS thru ColdFusion without any problems. If you are in ColdFusion 7, then you need a postgresql driver installed, but I do suggest you use ColdFusion 8 as the driver is built-in.

To display the geometry, I typically use AsGML output from PostGIS and supply that path to OpenLayers. Although it works as expected, I need to invest in two (2) http calls to the server:

1st Request: Call search.cfm and get the attributes (name, address, tel_no, etc…). Afterwards, display the results on an Ext.Window.
2nd Request: Display the geometries on OpenLayers using GML.

We have decided in our organisation not to write out the javascript statements on AJAX calls but instead retrieve them as Data Objects (either XML or GeoJSON). Putting in javascript statements on AJAX calls seems harder to debug. GeoJSON is highly preferred for internet mapping applications since it has a unique ability to see the javascript objects quickly on the browser, making debugging easier.

I wrote a simple cfc below to be able to parse the geometry from PostGIS using AsText(geometry). The function accepts a geometry as string and returns a structure containing the type and the coordinates.

<cfcomponent displayname="GeoJSON" hint="I am a GeoJSON Component. I parse a geometry and return it as JSON" output="false">
 
	<cffunction name="init" access="public" output="false">
		<cfreturn>
	cfreturn>	
 
	cffunction><cffunction name="format" returntype="Struct" output="false">
		<cfargument name="geomtext" type="String" required="true">
		<cfset>
		cfset><cfset>
		cfset><cfset geometry="StructNew()">
		cfset><cfset>
		cfset><cfset>
		cfset><cfset>
		cfset><cfset>
		cfset><cfset>
 
		cfset><cfset geometry.type="Mid(arguments.geomtext,">
		cfset><cfset>
 
		cfset><cfset geomreplacedbrackets="Replace(arguments.geomtext,">
		cfset><cfset geomreplacedbrackets="Replace(geomReplacedBrackets,">
 
		<cfloop from="1" to="#Len(geomReplacedBrackets)#" index="i">
			<cfset curchar="Mid(geomReplacedBrackets,">
			<cfif>
				<cfset geometry.coordinates="geometry.coordinates">
	    		cfset><cfset secchar="Mid(geomReplacedBrackets,">
				<cfif> 
					<cfset posi="i"> 
					cfset><cfset posj="find(']',">
					cfset><cfset tempgeom="Mid(geomReplacedBrackets,">
					cfset><cfset i="posJ"> 
 
					cfset><cfset>
 
					<cfloop list="#tempGeom#" index="tempGeomIndex" delimiters=",">
						<cfset tempvalue="[">
						cfset><cfset geomreplaced="ListAppend(geomReplaced,">
					cfset>cfloop>cfset>
 
					<cfset geometry.coordinates="geometry.coordinates">
				cfset>cfif>cfset>cfif>cfset>cfloop>
			<cfelseif>
				<cfset geometry.coordinates="geometry.coordinates">
			cfset>cfelseif>cfset>
 
		<cfset geometry.coordinates="Replace(geometry.coordinates,">
 
		<cfif>
			<cfset geometry.coordinates="Replace(geometry.coordinates,">
			cfset><cfset geometry.coordinates="Replace(geometry.coordinates,">
		cfset>
 
		<cfreturn>
	cfreturn>cfif>cfset>
 
cfargument>cffunction>cfcomponent>

ExtJS and OpenLayers

rupert — Tue, 19 Feb 2008 00:45:18 +0000

It seems that ExtJS and OpenLayers does not blend well together. One of the bug biters that hit me was the way ExtJS was handling arrays. It would be wise for OpenLayers to be agnostic of these frameworks.

for( var i in blocks ) should be transformed to for( var i = 0; i &lt; blocks.length; i++)

I believe OpenLayers Ticket#1362 closely resembles this bug. Thanks to pgiraud for pointing me to the right direction.

ExtJS QuickTip: Display other levels of a JSON object in a Grid

rupert — Mon, 18 Feb 2008 15:08:39 +0000

You can display an item anywhere in a JSON heirarchy/level in a Grid by using dot notation. I am beginning to like JSON as it is simply practical and amazing. To fully understand, please see geometry.type as an example.

{ "type": "FeatureCollection", "recordcount":6, "features": [ { "type":"Feature", "geometry":{ "type": "MULTIPOLYGON", "coordinates": [[[[116.368603,39.944314],[116.381069,39.94464],[116.388765,39.940265],[116.390376,39.939124],[116.391203,39.934381],[116.391784,39.930743],[116.387262,39.930638],[116.387507,39.93289],[116.383032,39.932688],[116.382581,39.933204],[116.37197,39.940531],[116.368603,39.944314]]]] }, "gid":16055, "cn_name":"后海", "py_name": "hou hai" } , { "type":"Feature", "geometry":{ "type": "MULTIPOLYGON", "coordinates": ....}

Here is the DataStore…

cs.GridPlace = function(){
    var _placeDataStore = new Ext.data.Store({
        // create reader that reads the Topic records
        reader: new Ext.data.JsonReader({
            root: 'features',
            totalProperty: 'recordcount',
            id: 'gid',
            fields: [
                'cn_name', 'py_name', 'geometry.type'
            ]
        })
    });
 
    // the column model has information about grid columns
    // dataIndex maps the column to the specific data field in
    // the data store
    var cm = new Ext.grid.ColumnModel([{
           id: 'gid', // id assigned so we can apply custom css (e.g. .x-grid-col-topic b { color:#333 })
           header: "CN_NAME",
           width: 100,
           dataIndex: 'cn_name'
        },{
           id: 'gid', // id assigned so we can apply custom css (e.g. .x-grid-col-topic b { color:#333 })
           header: "PY_NAME",
           width: 100,
           dataIndex: 'py_name'
        },{
           id: 'gid', // id assigned so we can apply custom css (e.g. .x-grid-col-topic b { color:#333 })
           header: "GEOMTYPE",
           width: 100,
           dataIndex: 'geometry.type'
        }
    ]);

Reviving an old web map with Google Maps via OpenLayers

rupert — Tue, 22 Jan 2008 01:10:09 +0000

An old coworker and I worked on a travel portal for the Philippines called travelsite.ph about 4 years ago. We are now given a task of reviving the old web application and even adding mapping functionalities. Back then, the application was using ColdFusion 4.5 and MySQL 3.

Fingers crossed we dropped the app in a ColdFusion 6/7/8 environment with no changes at all. The app still works! Awesome.. how CF really progressed through the years with backward compatibility. The only changes we made was removing the registration/sign up for a quick demo. I just laughed at the oddities and the no brainer features (pertaining to security) that I made when I was starting out.

The database was also intact and have UTM coordinates. We dropped it to a Debian mysql 5 and works flawlessly since its MyISAM. I had the coordinates exported to lon/lat, so I could directly inject it to OpenLayers/Google. After two hours of fiddling around, I got mapping embedded.. hehe.. courtesy of OpenLayers ofcourse.

Here’s a quick reminder to myself…

A. Google WGS 84 Example.

	window.onload = function() {
		var options = {
					projection: "EPSG:4326",
					numZoomLevels: 19,
					maxExtent: new OpenLayers.Bounds(120.8774, 14.3684, 121.1628, 14.7931)
 
				};
 
		// avoid pink tiles
		OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
		OpenLayers.Util.onImageLoadErrorColor = "transparent";
		map = new OpenLayers.Map('mapdiv',options);
		sat_wms = new OpenLayers.Layer.Google(
					"Layer",
					{type: G_SATELLITE_MAP}
		);
 
		map.addLayer(sat_wms);
 
		map.addControl(new OpenLayers.Control.MousePosition();
		map.addControl(new OpenLayers.Control.LayerSwitcher());
		map.addControl(new OpenLayers.Control.Scale());
 
		var center = new OpenLayers.LonLat(121.06504,14.65495);
		map.setCenter(center, 16);
	}

B. Google Mercator Projection

		window.onload = function() {
			var options = {
						projection: "EPSG:900913",
						units: "m",
						maxResolution: 156543.0339,
						numZoomLevels: 19,
						maxExtent: new OpenLayers.Bounds(12823075.86334, 4800551.12375, 13101918.14248, 5021301.26141)
					};
 
			// avoid pink tiles
			OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
			OpenLayers.Util.onImageLoadErrorColor = "transparent";
			map = new OpenLayers.Map('mapdiv',options);
			sat_wms = new OpenLayers.Layer.Google(
						"Layer",
						{type: G_SATELLITE_MAP,'sphericalMercator': true}
			);
			map.addLayer(sat_wms);
 
			// start custom layer here
			var layer_obj = new OpenLayers.Layer.WMS(
				"Beijing",
				"http://127.0.0.1/cgi-bin/mapserv",
				{
					layers: 'beijing_all',
					map: '/home/map/beijing/new/beijing_google.map',
					format: 'AGG',
					'transparent': 'true'
				}
			);
			layer_obj.setIsBaseLayer(false);
			layer_obj.setVisibility(true);	
 
			map.addLayer(layer_obj);
 
			map.addControl(new OpenLayers.Control.MousePosition());
			map.addControl(new OpenLayers.Control.LayerSwitcher());
			map.addControl(new OpenLayers.Control.Scale());
			var center = new OpenLayers.LonLat(12956625.68367, 4852316.90682);
			map.setCenter(center, 18);
		}

What’s the difference between both snippets? Obviously projection is one. Since most of my point data is in lon/lat, then the WGS84 example is good if I don’t want to overlay custom precise data. Remember the x shift problem in Google with Openlayers. The Google Mercator example is used when I want to overlay more custom data, particularly polygons/line that needs to fit on Google Layers. For more details, please see my previous blog post.

Passing Parameters to Mapserver

rupert — Thu, 03 Jan 2008 22:27:19 +0000

I was bitten 4 hours searching for this in the mailing list. I have a postgis layer defined in mapserver map file as follows:

LAYER
        NAME "pois"
        STATUS DEFAULT
		GROUP "pois"
        TYPE POINT
 
		CONNECTIONTYPE postgis
		PROCESSING "CLOSE_CONNECTION=DEFER"
		CONNECTION "user=lbs password=xtlme15n dbname=beijing_stat host=192.168.1.211 port=5432"
		#DATA "the_geom from (SELECT poi_id, the_geom FROM poi WHERE new_block_id = 7) as foo USING UNIQUE poi_id USING SRID=4326"
		DATA "the_geom from poi as foo USING UNIQUE poi_id USING SRID=4326"
 
		FILTER "new_block_id=%myid%"
 
		CLASS
			NAME "block-pois"
    		        STYLE
				SYMBOL "circle"
     			        COLOR 255 0 0
				SIZE 10
   			END
  		END
END

Traditionally, I could append and change the FILTER attribute by passing it to the Mapserver CGI as follows:
map.pois.filter=new_block_id%3D700.

Apparently, this changed with Mapserver 5.0. Please see MapServer 4.10 to 5.0 Migration Guide. Thanks to this mailing list thread, it turned out that we need to pass a value to a custom variable set in the mapfile for security reasons. Hope this one, goes in to the docs. I was hoping to comment out in the Mapserver Documentation but registration is holding me off with a ‘Connection Refused’.

OpenLayers + Google Spherical Mercator Example

rupert — Sat, 22 Dec 2007 11:42:18 +0000

I’ve been a dormant user of OpenLayers for months (4 months?) now and it was a surprise that the svn trunk had huge differences from what I remember OL (2.4/5?) to be. One of the cool features that and the OpenLayers community contributed was the Google Speherical Mercator hack. Below is a quick step tutorial on how I was able to overlay a custom WMS to Google (set as the baselayer). For this tutorial, I want to overlay a road layer on top of Google.

1. We need to convert our data to Google Projection (Spatial Reference System: 900913). This applies to whatever kind of data (mine is vector stored both in Mapinfo and PostGis) we have. For PostGis, we need to:

INSERT INTO spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) VALUES ( 900913, 
 
'spatialreference.org', 900913, '+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 
 
+x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs', 'PROJCS
 
["unnamed",GEOGCS["unnamed ellipse",DATUM["unknown",SPHEROID["unnamed",6378137,0]],PRIMEM
 
["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Mercator_2SP"],PARAMETER
 
["standard_parallel_1",0],PARAMETER["central_meridian",0],PARAMETER
 
["false_easting",0],PARAMETER["false_northing",0],UNIT["Meter",1],EXTENSION
 
["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 
 
+units=m +nadgrids=@null +wktext  +no_defs"]]');
 
SELECT AddGeometryColumn('public','roads','the_geom_google',900913,'LINESTRING',2); 
 
UPDATE roads SET the_geom_google = Transform(the_geom, 900913);

2. MapFile Settings courtesy of SpatialReference: Google Projection

WEB
    #Other Web Config Settings goes here...
    "wms_srs"              "EPSG:900913"
END
 
PROJECTION
    "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs"
END

3. By ensuring that Mapserver has the new 900913 projection, problems such as “msWMSLoadGetMapParams(): WMS server error. Invalid SRS given : SRS must be valid for all requested layers.” or “msProcessProjection(): Projection library error. no options found in ‘init’ file” will be avoided.

cd /ms4w/proj/nad/
gvim epsg
# GCS Voirol 1875 Degree
<104304> +proj=longlat +a=6378249.2 +b=6356514.999904194  no_defs <>
# GCS Voirol Unifie 1960 Degree
<104305> +proj=longlat +ellps=clrk80  no_defs <>
# Google Spherical Mercator
. . .
<900913> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs

4. Below is an example WMS Request. Note: “SRS=EPSG 900913″ is added; TRANSPARENT=true not TRANSPARENT=on; Check your BBOX settings for the correct extent.

http://127.0.0.1/cgi-bin/mapserv?
LAYERS=beijing_all
&MAP=%2Fhome%2Fmap%2Fbeijing%2Fnew%2Fbeijing_google.map
&FORMAT=AGG
&TRANSPARENT=true
&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap
&STYLES=
&EXCEPTIONS=application%2Fvnd.ogc.se_inimage
&SRS=EPSG%3A900913
&BBOX=12956687.788758555,4852222.554861524,12956993.536871642,4852528.30297461
&WIDTH=256&HEIGHT=256

5. Requesting the WMS from OpenLayers.

	var options = {
			projection: "EPSG:900913",
			units: "m",
			//maxResolution: 156543.0339,
			numZoomLevels: 18,
			maxExtent: new OpenLayers.Bounds(12823075.86334, 4800551.12375, 13101918.14248, 021301.26141)
	};
 
	// avoid pink tiles
	OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
	OpenLayers.Util.onImageLoadErrorColor = "transparent";
	map = new OpenLayers.Map('mapdiv',options);
	sat_wms = new OpenLayers.Layer.Google(
				"Layer",
				{type: G_SATELLITE_MAP,'sphericalMercator': true}
	);
	map.addLayer(sat_wms);
 
	// start custom layer here
	var layer_obj = new OpenLayers.Layer.WMS(
		"Beijing",
		"http://127.0.0.1/cgi-bin/mapserv",
		{
			layers: 'beijing_all',
			map: '/home/map/beijing/new/beijing_google.map',
			format: 'AGG',
			'transparent': 'true'
		}
	);
	layer_obj.setIsBaseLayer(false);
	layer_obj.setVisibility(true);	
 
        map.addLayer(layer_obj);
	map.addControl(new OpenLayers.Control.MousePosition());
	map.addControl(new OpenLayers.Control.LayerSwitcher());
	map.addControl(new OpenLayers.Control.Scale());
 
	var center = new OpenLayers.LonLat(12956625.68367, 4852316.90682);
	map.setCenter(center, 17);

GIS 2.0

rupert — Fri, 21 Dec 2007 02:48:10 +0000

It’s been a long time since my previous blog post because I was caught up with numerous meetings and presentations with the recent development of “The Interface“. Developing the new beast during a 2.5 week code sprint is both enjoyable and a personal satisfaction. I have to give credit to Yahoo UI and ExtJS for a wonderful javascript library that they opened to the public. Without ExtJS, I don’t think it would be possible to create such an interactive, compelling and impressive interface for my demos.

Web 2.0 has given me a chance to wrap our traditional GIS processes/solutions into a high impact presentation for our marketing/business developments. Thus, it was not a suprise to see that CamptoCamp’s Mapfish is also using extjs. It has aided me very well in data analysis and visualisation. It may just be a meaningless term to others, however I believe we just entered the start of GIS 2.0…

Reflecting… I believe it is worth investing in learning PostGIS in-depth. Though it may appear fascinating to others that a group of small applications (which I called the core platform utilising Nearest Neighbor Searching and Geometric Unions) bundled together in a Web2.0 interface is impressive, I believe I only scratched the surface of what and how PostGIS should be used. I wanted to do more, but my busy work schedule begs to finish other components of our product.

To be continued…

Geometric Algorithms in GIS

rupert — Fri, 16 Nov 2007 10:33:31 +0000

Here is a couple of Geometric Algorithms used in GIS.

Convex hull problem: for a set of points, determine the smallest convex set that contains all.

Line segment intersection: for a set of line segments, determine all intersections.

Voronoi diagram computation: for a set of points, determine the subdivision of the plane into cells such that inside some cell, one and the same point of the set is closest.

Delaunay triangulation: for a set of points, determine a planar subdivision by creating edges between the input points in such a way that no two edges intersect, all faces are triangles, no more edges can be added with the given constraints, and no circumcircle of any triangle contains an input point in its interior.

Minkowski sum: for two simple polygons P and Q, compute the shape that consist exactly of the sum of all points of P and all points of Q, where sum is interpreted as the vector sum.

Rectangular range search: for a set of points in the plane, design a data structure on those points, such that for every axis-parallel query rectangle, all points in the data structure that lie in the query rectangle can be reported efficiently. Algorithms are needed for the construction of the data structure and for the execution of a query.

Reference:
M Kreveld, Computational Geometry: Its objectives and relation to GIS, Institute of Information and Computing Sciences, Utrecht University

Installing R on Windows and Debian

rupert — Fri, 16 Nov 2007 01:15:59 +0000

‘R’ is a statistical package. For an overview, please go to www.r-project.org
My intention was to remove the point outliers from a given set of point geometries.

I just recently installed R both on my Windows XP and Debian. Regina’s www.bostongis.com is an excellent tutorial in getting involved with R. I do suggest you head first to PLR Part 1: Up and Running with PL/R (PLR) in PostgreSQL: An almost Idiot’s Guide to get you started.

The install instructions for Windows works flawlessly. I have to hold back to R-2.5 though as I plan to use RPy (Python for R), see details below. To install ‘R’ in Debian, there’s a couple of settings that we need to take care of…

1. Install r-base
sudo apt-get install r-base

2. Install plr on postgres
sudo apt-get install postgresql-8.2-plr

3. Using R in a database
psql -d beijing -U lbs -h 127.0.0.1 < /usr/share/postgresql/8.2/plr.sql

4. Set the R_HOME environment variable
/etc/postgresql/8.2/main/environment
R_HOME='/usr/lib/R'

5. Restart Debian.

RPy, R for Python, is another alternative to use R in Python. I installed it both in Windows and Debian. Note that I reverted to R-2.5 on Windows to be compatible with RPy. For Debian, Im currently using R-2.6.

For the Windows Binary Installation,

1. Read the RPy Main Site

2. Install prerequisites:

- NumPy
- Win32 Extensions Download

3. Afterwards, install the main package, RPy Download

In Debian, its a straight forward…sudo apt-get install python-rpy