[Mapserver-users] documentation bug (was Re: projecting a point
in PHP MapScript)
Chris Black
cblack at CalAcademy.Org
Wed Mar 5 14:21:18 EST 2003
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Ok, I've stepped up to 3.7, which I downloaded as
mapserver-3.7-win32-php4.3.0-gd2.zip from
http://www2.dmsolutions.ca/mapserver/dl/ (since I'm on Windows, I'm
trying to avoid doing any compilation myself).
The behavior has changed somewhat; I now get an explicit failed return
code and an error message. I'm still not succeeding. Is there any way
to get a more explicit error message about why the projection is
failing? Is there a different 3.7 binary and libraries I should try?
Thanks.
-- Chris
my code:
----------------
1 <?php
2
3 dl('php_mapscript_37.dll');
4
5 $outproj =
ms_newProjectionObj("proj=utm,zone=10,datum=NAD27,ellps=clrk66,units=m,no_defs,north");
6 $inproj = ms_newProjectionObj("proj=longlat,ellps=clrk66");
7
8 $crab_here = ms_newpointobj();
9 $crab_here->setXY(38.20527700, -122.37277700);
10 $retval = $crab_here->project($inproj, $outproj);
11 if ($retval == MS_SUCCESS) {print("Succeeded. ");} else
{print("Failed. ");}
12 print(" x is ");
13 print($crab_here->x);
14 print("; y is ");
15 print($crab_here->y);
16 ?>
-------------------------
output with error message:
-----------------------
Warning: MapServer Error in : in c:\inetpub\scripts\debug_projection.php
on line 10
Failed. x is 38.205277; y is -122.372777
---------------------------------
metadata describing the map I want to print the point onto, and from
which I am therefore taking the definition of $outproj:
------------------------
SPATIAL_REFERENCE_INFORMATION
Horizontal_Coordinate_System_Definition
Planar
Grid_Coordinate_System
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 10
Transverse_Mercator
Scale_Factor_at_Central_Meridian: implied
Longitude_of_Central_Meridian: implied
Latitude_of_Projection_Origin: implied
False_Easting: implied
False_Northing: implied
Planar_Coordinate_Information
Planar_Coordinate_Encoding_Method: Row and column
Coordinate_Representation:
Abscissa_Resolution: 30.0
Ordinate_Resolution: 30.0
Planar_Distance_Units: Meters
Geodetic_Model
Horizontal_Datum_Name: North American Datum 1927
Ellipsoid_Name: Clarke 1866
Semi-major_Axis: 6378206.4
Denominator_of_Flattening_Ratio: 294.98
----------------------
Daniel Morissette wrote:
>Chris Black wrote:
>
>
>>Eric Bridger wrote:
>>
>>
>>
>>>Chris,
>>>1) pointObj->project() does not return a point, it just reprojects the
>>>pointObj, so getting a null is not an error.
>>>
>>>
>>>
>>In that case, the online PHP class documentation should be modified.
>> The doc at
>>http://mapserver.gis.umn.edu/doc36/phpmapscript-class-guide.html#proj
>>has this code snippet:
>>
>>
>>
>
>Actually the 3.6 version "tries to" return a point but it's broken, it
>returns a point with an invalid internal poinObj reference, and the
>initial object is updated internally but the PHP wrapper is not, if you
>continue to play with the returned object you'll eventually end up with
>a crash. In 3.7 it won't return a point any more, instead it updates
>the point on which the project() method is called.
>
>I think your problem is simply that the project() method is broken in
>3.6 and cannot be relied upon. I'll see if I could backport the 3.7
>changes to 3.6, I just hoped that we could avoid that since very few
>people seemed to use those methods. The other option would be for you
>to use 3.7 in which the project() method works very well.
>
>
>
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Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title></title>
</head>
<body>
Ok, I've stepped up to 3.7, which I downloaded as mapserver-3.7-win32-php4.3.0-gd2.zip
from <a class="moz-txt-link-freetext" href="http://www2.dmsolutions.ca/mapserver/dl/">http://www2.dmsolutions.ca/mapserver/dl/</a> (since I'm on Windows, I'm
trying to avoid doing any compilation myself).<br>
<br>
The behavior has changed somewhat; I now get an explicit failed return code
and an error message. I'm still not succeeding. Is there any way to get
a more explicit error message about why the projection is failing? Is there
a different 3.7 binary and libraries I should try?<br>
<br>
Thanks.<br>
<br>
-- Chris<br>
<br>
my code:<br>
----------------<br>
1 <?php<br>
2<br>
3 dl('php_mapscript_37.dll'); <br>
4<br>
5 $outproj = ms_newProjectionObj("proj=utm,zone=10,datum=NAD27,ellps=clrk66,units=m,no_defs,north");<br>
6 $inproj = ms_newProjectionObj("proj=longlat,ellps=clrk66");<br>
7<br>
8 $crab_here = ms_newpointobj();<br>
9 $crab_here->setXY(38.20527700, -122.37277700);<br>
10 $retval = $crab_here->project($inproj, $outproj);<br>
11 if ($retval == MS_SUCCESS) {print("Succeeded. ");} else {print("Failed.
");}<br>
12 print(" x is ");<br>
13 print($crab_here->x);<br>
14 print("; y is ");<br>
15 print($crab_here->y);<br>
16 ?><br>
-------------------------<br>
output with error message:<br>
-----------------------<br>
<br>
<b>Warning</b>: MapServer Error in : in <b>c:\inetpub\scripts\debug_projection.php</b>
on line <b>10</b><br>
Failed. x is 38.205277; y is -122.372777<b><br>
---------------------------------<br>
</b>metadata describing the map I want to print the point onto, and from
which I am therefore taking the definition of $outproj:<br>
------------------------<br>
SPATIAL_REFERENCE_INFORMATION<br>
<br>
<br>
<br>
Horizontal_Coordinate_System_Definition<br>
<br>
Planar<br>
<br>
Grid_Coordinate_System<br>
<br>
Grid_Coordinate_System_Name: Universal Transverse Mercator<br>
<br>
Universal_Transverse_Mercator:<br>
<br>
UTM_Zone_Number: 10<br>
<br>
Transverse_Mercator<br>
<br>
Scale_Factor_at_Central_Meridian: implied<br>
<br>
Longitude_of_Central_Meridian: implied<br>
<br>
Latitude_of_Projection_Origin: implied<br>
<br>
False_Easting: implied<br>
<br>
False_Northing: implied<br>
<br>
Planar_Coordinate_Information<br>
<br>
Planar_Coordinate_Encoding_Method: Row and column<br>
<br>
Coordinate_Representation:<br>
<br>
Abscissa_Resolution: 30.0<br>
<br>
Ordinate_Resolution: 30.0<br>
<br>
Planar_Distance_Units: Meters<br>
<br>
Geodetic_Model<br>
<br>
Horizontal_Datum_Name: North American Datum 1927<br>
<br>
Ellipsoid_Name: Clarke 1866<br>
<br>
Semi-major_Axis: 6378206.4<br>
<br>
Denominator_of_Flattening_Ratio: 294.98<br>
<br>
----------------------<br>
<b><br>
</b><br>
<br>
<br>
Daniel Morissette wrote:<br>
<blockquote type="cite" cite="mid3E6526D6.1EF85B21 at dmsolutions.ca">
<pre wrap="">Chris Black wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Eric Bridger wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Chris,
1) pointObj->project() does not return a point, it just reprojects the
pointObj, so getting a null is not an error.
</pre>
</blockquote>
<pre wrap="">In that case, the online PHP class documentation should be modified.
The doc at
<a class="moz-txt-link-freetext" href="http://mapserver.gis.umn.edu/doc36/phpmapscript-class-guide.html#proj">http://mapserver.gis.umn.edu/doc36/phpmapscript-class-guide.html#proj</a>
has this code snippet:
</pre>
</blockquote>
<pre wrap=""><!---->
Actually the 3.6 version "tries to" return a point but it's broken, it
returns a point with an invalid internal poinObj reference, and the
initial object is updated internally but the PHP wrapper is not, if you
continue to play with the returned object you'll eventually end up with
a crash. In 3.7 it won't return a point any more, instead it updates
the point on which the project() method is called.
I think your problem is simply that the project() method is broken in
3.6 and cannot be relied upon. I'll see if I could backport the 3.7
changes to 3.6, I just hoped that we could avoid that since very few
people seemed to use those methods. The other option would be for you
to use 3.7 in which the project() method works very well.
</pre>
</blockquote>
<br>
</body>
</html>
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