.. _faq:
***************************************************
FAQ
***************************************************
Where is the MapServer log file?
-------------------------------------------------------------------------------
See :ref:`rfc28`
What books are available about MapServer?
-------------------------------------------------------------------------------
`"Mapping Hacks" `__ by Schuyler
Erle, Rich Gibson, and Jo Walsh is available from O'Reilly.
`"Web Mapping Illustrated" `__ by Tyler
Mitchell is available from O'Reilly. Introduces MapServer and many other
related technologies including, GDAL/OGR, MapScript, PostGIS, map projections,
etc.
`"MapServer: Open Source GIS Development"
`__ by Bill Kropla.
How do I compile MapServer for Windows?
-------------------------------------------------------------------------------
See :ref:`win32`. Also, you can use the development libraries in :ref:`OSGeo4W
` as a starting point instead of building all of the dependent
libraries yourself.
What do MapServer version numbers mean?
-------------------------------------------------------------------------------
MapServer's version numbering scheme is very similar to Linux's. For example,
a MapServer version number of 4.2.5 can be decoded as such:
- 4: Major version number. MapServer releases a major version every two to
three years.
- 2: Minor version number. Increments in minor version number almost always
relate to additions in functionality.
- 5: Revision number. Revisions are bug fixes only. No new functionality is
provided in revisions.
From a developer's standpoint, MapServer version numbering scheme is also like
Linux. Even minor version numbers (0..2..4..6) relate to *release* versions,
and odd minor versions (1..3..5..7) correspond to developmental versions.
Is MapServer Thread-safe?
-------------------------------------------------------------------------------
**Q**: Is MapServer thread-safe?
**A**: Generally, no (but see the next question). Many components of MapServer
use static or global data that could potentially be modified by another
thread. Under heavy load these unlikely events become inevitable, and could
result in sporadic errors.
**Q**: Is it possible to safely use any of MapServer in a multi-threaded
application?
**A**: Some of it, yes, with care. Or with Python :) Programmers must either
avoid using the unsafe components of MapServer or carefully place locks around
them. Python's global interpreter lock immunizes against MapServer threading
problems; since no mapscript code ever releases the GIL all mapscript
functions or methods are effectively atomic. Users of mapscript and Java,
.NET, mod_perl, or mod_php do not have this extra layer of protection.
**A**: Which components are to be avoided?
**Q**: Below are lists of unsafe and unprotected components and unsafe but
locked components.
Unsafe:
- OGR layers: use unsafe CPL services
- Cartoline rendering: static data
- Imagemap output: static data
- SWF output: static data and use of unsafe msGetBasename()
- SVG output: static data
- WMS/WFS server: static data used for state of dispatcher
- Forcing a temporary file base (an obscure feature): static data
- MyGIS: some static data
Unsafe, but locked:
- Map config file loading: global parser
- Setting class and and layer filter expressions (global parser)
- Class expression evaluation (global parser)
- Setting map and layer projections (PROJ)
- Raster layer rendering and querying (GDAL)
- Database Connections (mappool.c)
- PostGIS support
- Oracle Spatial (use a single environment handle for connection)
- SDE support (global layer cache)
- Error handling (static repository of the error objects)
- WMS/WFS client connections: potential race condition in Curl initialization
- Plugin layers (static repository of the loaded dll-s)
Rather coarse locks are in place for the above. Only a single thread can use
the global parser at a time, and only one thread can access GDAL raster data
at a time. Performance is exchanged for safety.
What does STATUS mean in a LAYER?
-------------------------------------------------------------------------------
STATUS ON and STATUS OFF set the default status of the layer. If a map is
requested, those layers will be ON/OFF unless otherwise specified via the
layers parameter. This is particularly the case when using MapScript and
MapServer's built-in template mechanism, but is also useful as a hint when
writing your own apps and setting up the initial map view.
STATUS DEFAULT means that the layer is always on, even if not specified in the
layers parameter. A layer's status can be changed from DEFAULT to OFF in
MapScript, but other than that, it's always on.
:ref:`cgi` turns everything off that is not "STATUS DEFAULT" off so all layers
start from the same state (e.g. off) and must be explicitly requested to be
drawn or query. That common state made (at least in my mind) implementations
easier. I mean, if a layer "lakes" started ON the doing layer=lakes would turn
it OFF. So I wanted to remove the ambiguity of a starting state.
How can I make my maps run faster?
-------------------------------------------------------------------------------
There are a lot of different approaches to improving the performance of your
maps, aside from the obvious and expensive step of buying faster hardware.
Here are links to some individual howtos for various optimizations.
* :ref:`Tuning your mapfile for performance `
* :ref:`Optimizing the performance of vector data sources `
* :ref:`Optimizing the performance of raster data sources `
* :ref:`Tileindexes for mosaicing and performance `
Some general tips for all cases:
* First and foremost is hardware. An extra GB of RAM will give your map
performance increases beyond anything you're likely to achieve by tweaking
your data. With the price of RAM these days, it's cheap and easy to speed up
every map with one inexpensive upgrade.
* Use the scientific method. Change one thing at a time, and see what effect
it had. Try disabling all layers and enabling them one at a time until you
discover which layer is being problematic.
* Use :ref:`shp2img` program to time your results. This runs from
the command line and draws an image of your entire map. Since it's run from
the command line, it is immune to net lag and will give more consistent
measurements that your web browser.
What does Polyline mean in MapServer?
-------------------------------------------------------------------------------
There's confusion over what POLYLINE means in MapServer and via ESRI. In
MapServer POLYLINE simply means a linear representation of POLYGON data. With
ESRI polyline means multi-line. Old versions of the Shapefile techical
description don't even refer to polyline shapefiles, just line. So, ESRI
polyline shapefiles are just linework and can only be drawn and labeled as
LINE layers. Those shapefiles don't have feature closure enforced as polygon
shapefiles do which is why the distinction is so important. I suppose there is
a better choice than POLYLINE but I don't know what it would be.
.. note::
The only difference between POLYLINE and LINE layers is how they are
labeled.
What is MapScript?
-------------------------------------------------------------------------------
MapScript is the scripting interface to MapServer, usually generated by
:term:`SWIG` (except in the case of :ref:`php_mapscript`).
MapScript allows you to program with MapServer's objects directly
instead of interacting with MapServer through its :ref:`cgi` and
:ref:`mapfile`.
Does MapServer support reverse geocoding?
-------------------------------------------------------------------------------
No.
Reverse geocoding is an activity where you take a list of street features that
you already have and generate postal addresses from them. This kind of spatial
functionality is provided by proprietary packages such as the ESRI suite of
tools, as well as services such as those provided by GDT. MapServer is for
*map rendering*, and it does not provide for advanced spatial operations such
as this.
Does MapServer support geocoding?
-------------------------------------------------------------------------------
No.
Geocoding is an activity where you take a list of addresses and generate
lat/lon points for them. This kind of spatial functionality is provided by
proprietary packages such as the ESRI suite of tools, as well as services such
as those provided by GDT. MapServer is for *map rendering*, and it does not
provide for advanced spatial operations such as this.
If you are using MapScript, there is a free geocder available through XMLRPC
and SOAP at http://geocoder.us . You could hook you application up to use this
service to provide lat/lon pairs for addresses, and then use MapServer to
display those points.
How do I set line width in my maps?
-------------------------------------------------------------------------------
In the current Mapserver version, line width is set using
the STYLE parameter WIDTH. For a LINE layer, lines can be
made red and 3 pixels wide by using the following style in
a CLASS.
.. code-block:: mapfile
STYLE
COLOR 255 0 0
WIDTH 3
END
In earlier versions of Mapserver, you could set the symbol for the
LAYER to 'circle' and then you can set the symbol SIZE to be the
width you want. A 'circle' symbol can be defined as
.. code-block:: mapfile
SYMBOL
NAME 'circle'
TYPE ELLIPSE
FILLED TRUE
POINTS 1 1 END
END
Why do my JPEG input images look crappy via MapServer?
-------------------------------------------------------------------------------
You must be using an old version of Mapserver (where GD was the
default library for rendering).
Newer versions of Mapserver use AGG for rendering, and the default
output formats is 24 bit colour, so there should not be a problem.
The default output format for MapServer with GD was 8bit
pseudo-colored PNG or GIF. Inherently there will be some color
degradation in converting a 24bit image (16 million colors) image into
8bit (256 colors).
With GD output, MapServer used quite a simple method to do the
transformation, converting pixels to the nearest color in a 175 color
colorcube. This would usually result in blotchy color in a fairly
smoothly varying image.
For GD, solutions used to be:
- Select 24bit output. This might be as easy as "IMAGETYPE JPEG" in your MAP
section.
- Enable dithering (PROCESSING "DITHER=YES") to produce a better color
appearance.
- Preprocess your image to 8bit before using it in MapServer with an external
application like the GDAL rgb2pct.py script.
For more information review the :ref:`raster`.
Which image format should I use?
-------------------------------------------------------------------------------
Although MapScript can generate the map in any desired image format it is
sufficient to only consider the three most prevalent ones: JPEG, PNG, and GIF.
JPEG is an image format that uses a lossy compression algorithm to reduce an
image's file size and is mostly used when loss of detail through compression
is either not noticeable or negligible, as in most photos. Maps on the other
hand mainly consist of fine lines and areas solidly filled in one colour,
which is something JPEG is not known for displaying very well. In addition,
maps, unless they include some aerial or satellite imagery, generally only use
very few different colours. JPEG with its 24bit colour depth capable of
displaying around 16.7 million colours is simple not suitable for this
purpose. GIF and PNG however use an indexed colour palette which can be
optimized for any number (up to 256) of colours which makes them the perfect
solution for icons, logos, charts or maps. The following comparison (generated
file sizes only; not file generation duration) will therefore only include
these two file formats:
.. table:: GIF vs. PNG vs. PNG24 Generated Map File Sizes
+------------------------------------------+-------+-------+-------+
| | GIF | PNG | PNG24 |
+==========================================+=======+=======+=======+
|Vector Data only | 59kb | 26kb | 69kb |
+------------------------------------------+-------+-------+-------+
|Vector Data & Satellite Image coloured | 156kb | 182kb | 573kb |
+------------------------------------------+-------+-------+-------+
|Vector Data & Satellite Image monochrome | 142kb | 134kb | 492kb |
+------------------------------------------+-------+-------+-------+
(results based on an average 630x396 map with various colours, symbols,
labels/annotations etc.)
Although GIF shows a quantitative as well as qualitative advantage over PNG
when generating maps that contain full coloured remote sensing imagery, PNG is
the clear quantitative winner in terms of generated file sizes for maps with
or without additional monochrome imagery and should therefore be the
preferred image format. If the mapping application however can also display
fullcolour aerial or satellite imagery, the output file format can be changed
dynamically to either GIF or even PNG24 to achieve the highest possible image
quality.
Why doesn't PIL (Python Imaging Library) open my PNGs?
-------------------------------------------------------------------------------
`PIL `__ does not support interlaced
PNGs at this time (no timetable on when it actually will either). To be able
to read PNGs in PIL, they must not be interlaced. Modify your OUTPUTFORMAT with
a FORMATOPTION like so:
.. code-block:: mapfile
OUTPUTFORMAT
NAME png
DRIVER "GD/PNG"
MIMETYPE "image/png"
IMAGEMODE RGB
EXTENSION "png"
FORMATOPTION "INTERLACE=OFF"
END
Why do my symbols look poor in JPEG output?
-------------------------------------------------------------------------------
When I render my symbols to an 8bit output (PNG, GIF) they look fine, but in
24bit jpeg output they look very blocky and gross.
You must be using an old version of Mapserver. This should not be
problem with newer versions. The following explains the old (GD)
behaviour.
In order to render some classes of symbols properly in 24bit output, such as
symbols from true type fonts, it is necessary to force rendering to occur in
RGBA. This can be accomplished by including the "TRANSPARENCY ALPHA" line in
the layer definition. Don't use this unnecessarily as there is a performance
penalty.
This problem also affects PNG24 output or any RGB output format. 8bit (PC256)
or RGBA output types are already ok.
How do I add a copyright notice on the corner of my map?
-------------------------------------------------------------------------------
You can use an inline feature, with the :ref:`FEATURE` object, to make a point on
your map. Use the TEXT parameter of the FEATURE object for the actual text of
the notice, and a :ref:`LABEL` object to style the notice.
Example Layer
...............................................................................
.. code-block:: mapfile
LAYER
NAME "copyright"
STATUS ON
TYPE annotation
TRANSFORM ll #set the image origin to be lower left
FEATURE
POINTS
60 -10 #set the offset from lower left position in pixels
END
TEXT "© xyz company 2006" #this is your displaying text
END
CLASS
LABEL #defines the font, colors etc. of the text
FONT "sans"
TYPE TRUETYPE
SIZE 8
BUFFER 1
COLOR 0 0 0
# BACKGROUNDCOLOR 255 255 255 # old way
FORCE TRUE
STYLE # new in mapserver 6
GEOMTRANSFORM 'labelpoly'
COLOR 255 255 255
END # STYLE
END
END
UNITS PIXELS #sets the units for the feature object
END
Result
...............................................................................
.. image:: ./images/copyright-image.png
How do I have a polygon that has both a fill and an outline with a width?
-------------------------------------------------------------------------------
How do I have a polygon that has both a fill and an outline with a width?
Whenever I put both a color (fill) and an outlinecolor with a width on a
polygon within a single STYLE, the outline width isn't respected.
For historical reasons, width has two meanings within the context of filling
polygons and stroke widths for the outline. If a polygon is filled, then the
width defines the width of the symbol *inside* the filled polygon. In this
event, the outline width is disregarded, and it is always set to 1. To acheive
the effect of *both* a fill and an outline width, you need to use two styles
in your class.
.. code-block:: mapfile
STYLE # solid fill
COLOR 255 0 0
END
STYLE # thick outline
OUTLINECOLOR 0 0 0
WIDTH 3
END
How can I create simple antialiased line features?
-------------------------------------------------------------------------------
With AGG (used in recent Mapserver version), antialiased lines is the
default, and can't be turned off.
With GD, the easiest way to produce antialiased lines is to:
- use a 24-bit output image type (IMAGEMODE RGB (or RGBA))
- set TRANSPARENCY ALPHA in the layer using antialiased lines
- set ANTIALIAS TRUE in the STYLE element of the CLASS with antialiased lines
The following mapfile snippets enable antialiased county borders for
GD:
.. code-block:: mapfile
...
IMAGETYPE "png24"
...
OUTPUTFORMAT
NAME "png24"
DRIVER "GD/PNG"
MIMETYPE "image/png"
IMAGEMODE RGB
EXTENSION "png"
END
...
LAYER
NAME "counties"
TYPE line
STATUS default
DATA "bdry_counln2"
TRANSPARENCY alpha
SYMBOLSCALE 5000000
CLASS
STYLE
WIDTH 3
COLOR 1 1 1
ANTIALIAS true
END
END
END
...
.. note::
The bdry_counln2 shapefile referenced in the counties layer is a line
shapefile. A polygon shapefile could be substituted with roughly the same
results, though owing to the nature of shapefiles each border would be
rendered twice and the resulting output line would likely appear to be
slightly thicker. Alternatively, one could use a polygon shapefile, set
TYPE to POLYGON, and use OUTLINECOLOR in place of COLOR in the STYLE
element.
.. note::
You can tweak the combination of STYLE->WIDTH and SYMBOLSCALE to modify
line widths in your output images.
.. seealso::
:ref:`Cartoline ` symbols can be used to achieve fancier
effects.
Which OGC Specifications does MapServer support?
-------------------------------------------------------------------------------
See: :ref:`ogc_support`.
Why does my requested WMS layer not align correctly?
-------------------------------------------------------------------------------
Requesting a layer from some ArcIMS WMS connectors results in a map with
misalgned data (the aspect ratio of the pixels looks wrong).
Some ArcIMS sites are not set up to stretch the returned image to fit the
requested envelope by default. This results in a map with data layers that
overlay well in the center of the map, but not towards the edges. This can be
solved by adding "*reaspect=false*" to the request (by tacking it on to the
connection string).
For example, if your mapfile is in a projection other than EPSG:4326, the
following layer will not render correctly:
.. code-block:: mapfile
LAYER
NAME "hillshade"
TYPE RASTER
STATUS OFF
TRANSPARENCY 70
CONNECTIONTYPE WMS
CONNECTION "http://gisdata.usgs.net:80/servlet19/com.esri.wms.Esrimap/USGS_WMS_NED?"
PROJECTION
"init=epsg:4326"
END
METADATA
"wms_srs" "EPSG:4326"
"wms_title" "US_NED_Shaded_Relief"
"wms_name" "US_NED_Shaded_Relief"
"wms_server_version" "1.1.1"
"wms_format" "image/png"
END
END
Adding "reaspect=false" to the connection string solves the problem:
.. code-block:: mapfile
LAYER
NAME "hillshade"
TYPE RASTER
STATUS OFF
TRANSPARENCY 70
CONNECTIONTYPE WMS
CONNECTION "http://gisdata.usgs.net:80/servlet19/com.esri.wms.Esrimap/USGS_WMS_NED?reaspect=false"
PROJECTION
"init=epsg:4326"
END
METADATA
"wms_srs" "EPSG:4326"
"wms_title" "US_NED_Shaded_Relief"
"wms_name" "US_NED_Shaded_Relief"
"wms_server_version" "1.1.1"
"wms_format" "image/png"
END
END
When I do a GetCapabilities, why does my browser want to download mapserv.exe/mapserv?
---------------------------------------------------------------------------------------
A beginner question here... I'm new to MS and to Apache. I've got MS4W up and
running with the Itasca demo. Now I want to enable it as a WMS server. mapserv
-v at the command line tells me it supports WMS_SERVER. When I point my
browser to it, my browser just wants to download mapserv.exe!
What am I missing?
Here is the URL I'm using to issue a GetCapabilities WMS request:
http://localhost/cgi-bin/mapserv.exe?map=../htdocs/itasca/demo.map&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetCapabilities
The OGC:WMS 1.1.0 and 1.1.1 specifications (which are both supported by
MapServer) state that, for GetCapabilities responses, the OGC:WMS server
returns a specific MIME type (i.e. application/vnd.ogc.xml (see subclause
6.5.3 of `OGC:WMS 1.1.1
`__.
A MIME type is passed from the web server to the client (in your case, a web
browser), from which a client can decide how to process it.
Example 1: if using a web browser, if a web server returns an HTTP Header of
"Content-type:image/png", then the web browser will know that this is a PNG
image and display it accordingly.
Example 2: if using a web browser, if a web server returns an HTTP Header of
"Content-type:text/html", then the web browser will know that this is an HTML
page and display it accordingly (i.e. tables, divs, etc.)
Basically, what is happening is that the OGC:WMS is returning, in the headers
of the HTTP response, a MIME type which your web browser does not understand,
which usually prompts a dialog box on whether to open or download the content
(i.e. Content-type:application/vnd.ogc.wms_xml).
You could configure your web browser to handle the application/vnd.ogc.wms_xml
MIME type a certain way (i.e. open in Notepad, etc.).
Why do my WMS GetMap requests return exception using MapServer 5.0?
-------------------------------------------------------------------------------
Before upgrading to MapServer 5.0, I was able to do quick GetMap tests in the
form of:
http://wms.example.com/wms?service=WMS&version=1.1.1&request=GetMap&layers=foo
Now when I try the same test, MapServer WMS returns an XML document saying
something about missing required parameters. What's going on here?
This was a major change for WMS Server support in MapServer 5.0. MapServer WMS
Server GetMap requests now require the following additional parameters:
* srs
* bbox
* width
* height
* format
* styles
.. note::
These parameters were always required in all versions of the WMS
specification, but MapServer previously had not required them in a client
request (even though most OGC WMS clients would issue them anyway to be
consistent with the WMS spec).
The request below now constitutes a valid GetMap request:
::
http://wms.example.com/wms?service=WMS&version=1.1.1&request=GetMap&layers=foo&srs=EPSG:4326&bbox=-180,-90,180,90&format=image/png&width=400&height=300&styles=default
Which is consistent with the WMS specification.
More information on these parameters can be found in the :ref:`wms_server` and
the `OGC WMS 1.1.1 specification
`__
For more detailed information, see `ticket 1088
`__
.. warning::
STYLES, though a required WMS parameter, is now optional again in
MapServer. For more detailed information, see `ticket 2427
`__
Using MapServer 6.0, why don't my layers show up in GetCapabilities responses or are not found anymore?
-------------------------------------------------------------------------------------------------------
MapServer 6.0 introduces the option of hiding layers against OGC Web Service
requests. OGC Web Services can provide powerful access to your geospatial
data. It was decided to disable layer level request access as a default. See
:ref:`rfc67` provides a full explanation of the changes and implications.
To enable pre-6.0 behaviour, you can add the following to the :ref:`WEB` object's METADATA section in your
mapfile:
::
"ows_enable_request" "*"
This will enable access of all layers to all OGC Web Service requests.
Where do I find my :term:`EPSG` code?
-------------------------------------------------------------------------------
There is a text file "epsg" in your PROJ4 installation (e.g.
"/usr/local/share/proj/epsg") which contain the EPSG information used by
PROJ4. In Windows, this is often located in C:\\proj\\nad or is found with an
environment variable called PROJ_LIB.
http://spatialreference.org allows you to search for EPSG codes.
You can also have a look at:
http://ocean.csl.co.uk
More information to EPSG:
http://www.epsg.org
More information to PROJ4:
http://trac.osgeo.org/proj
How can I reproject my data using ogr2ogr?
-------------------------------------------------------------------------------
With ogr2ogr of course! ogr2ogr is a powerful utility that will transform the
projections of your shapefiles when passed the appropriate parameters. In my
case, I was using MapServer to serve data in RI State Plane Feet. In order to
do so, the data had to first be converted to meters. Here is the command I
used:
::
ogr2ogr -t_srs EPSG:32130 output.shp input.shp
Since my data already had a projection defined, I did not need to explicitly
state a source projection. This command uses the EPSG definition for NAD83
Rhode Island (32130) and performs the feet to meters conversion.
Now say my data wasn't already projected? Here's how we deal with that:
::
ogr2ogr -s_srs "+proj=tmerc +lat_0=41.08333333333334 +lon_0=-71.5 +k=0.999994 +x_0=100000 +y_0=0 +ellps=GRS80 +datum=NAD83 +to_meter=0.3408 +no_defs" -t_srs EPSG:32130 output.shp input.shp
Let's examine what is going on here:
The -s_srs parameter explicitly defines a projection for the data. The
parameters used here were taken out of the EPSG definition (in this case,
32130) in the epsg file(see the `projection FAQ `__ for more
details on locating EPSG definitions). The entry for RI in the epsg file is as
follows:
::
# NAD83 / Rhode Island
<32130> +proj=tmerc +lat_0=41.08333333333334 +lon_0=-71.5 +k=0.999994 +x_0=100000 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs no_defs <>
You can see how the definition in the initial command is formulated. Notice
that the "+units=m" parameter has been changed to “+to_meter=0.3408”. This is
important for the conversion. Where did the value of 0.3408 come from you ask?
From the EPSG file! It has many goodies buried in it so by simply running
'grep "to_meter" epsg’ you can refresh your memory if you need to.
The next parameter in the command is "-t_srs EPSG:32130". This command tells
ogr2ogr to transform the data to the EPSG code of 32130. After this is
declared, all you need to do is declare a file name for your new shape file
and to set which file is being used as the input (note: make sure you don’t
confuse the order of these two).
Hit enter, bombs away, and enjoy your new data in meters!
How can I help improve the documentation on this site?
-------------------------------------------------------------------------------
New documentation material and corrections to existing documentation
are definitely very welcome. These contributions are handled through
the same issue tracker used to track software bugs and enhancements.
Follow the directions for submitting bugs at:
http://www.mapserver.org/development/bugs.html.
When creating a ticket, in the Component field, select `MapServer
Documentation`. If our ticket pertains to a specific web page, please
include the URL to that page.
If you have tips or examples that don't really fit the definition of
documentation, a good place to put them is the MapServer wiki at:
http://trac.osgeo.org/mapserver/wiki
What's with MapServer's logo?
-------------------------------------------------------------------------------
The MapServer logo illustrates the confluence of the `Minnesota`_ and `Mississippi`_
rivers, quite near to the home of the `St. Paul Campus`_ of the `University of Minnesota`_, which
was the `birthplace of MapServer`_.
.. _`Minnesota`: http://en.wikipedia.org/wiki/Minnesota_River
.. _`Mississippi`: http://en.wikipedia.org/wiki/Mississippi_River
.. _`St. Paul Campus`: http://en.wikipedia.org/wiki/University_of_Minnesota#St._Paul_campus
.. _`University of Minnesota`: http://en.wikipedia.org/wiki/University_of_Minnesota
.. _`birthplace of MapServer`: http://lists.osgeo.org/pipermail/mapserver-dev/2009-December/009435.html