<font color='black' size='2' face='arial'><font face="Georgia, Times New Roman, Times, Serif" size="2">I have been assuming that someone who knows something about proj would speak up. I don’t know anything about proj. However, Snyder’s formulation of Hammer includes a W parameter which controls the amount of bending in the parallels. The standard Hammar uses W = 1/2. Eckert-Greiffendorf uses W=1/4.<br>
<br>
Perhaps M is the horizontal compression/vertical exaggeration.<br>
<br>
To achieve Briesemeister under these assumptions, you would set W = 1/2, M = 0.93541 (or perhaps its reciprocal), and the projection center to 45°N. So, again, though I know nothing about proj, I assume you will need “ob_tran”, which I infer to mean oblique transformation or somesuch.<br>
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<div style="font-family: helvetica,arial; font-size: 10pt; color: black;">-----Original Message-----<br>
From: William Kyngesburye <woklist@kyngchaos.com><br>
To: PROJ.4 and general Projections Discussions <proj@lists.maptools.org><br>
Sent: Wed, Jan 19, 2011 11:47 am<br>
Subject: Re: [Proj] hammer parameters?<br>
<br>
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<pre style="font-size: 9pt;"><tt>So, can anyone tell me what the M and W parameters mean, or at least what values <br>
to use to get the Breisemeister (without using ob_tran)?<br>
<br>
On Jan 13, 2011, at 11:01 AM, William Kyngesburye wrote:<br>
<br>
> On Jan 12, 2011, at 5:33 PM, Frank Warmerdam wrote:<br>
> <br>
>> Folks,<br>
>> <br>
>> For what it is worth, it is possible to embed a literal PROJ.4 string<br>
>> in GDAL/OGR WKT in which case that will be used as the translation to<br>
>> PROJ.4 format.<br>
>> <br>
>> eg.<br>
>> PROJCS["UTM Zone 11, Northern Hemisphere",<br>
>> GEOGCS["WGS 84",<br>
>> DATUM["WGS_1984",<br>
>> SPHEROID["WGS 84",6378137,298.257223563,<br>
>> AUTHORITY["EPSG","7030"]],<br>
>> TOWGS84[0,0,0,0,0,0,0],<br>
>> AUTHORITY["EPSG","6326"]],<br>
>> PRIMEM["Greenwich",0,<br>
>> AUTHORITY["EPSG","8901"]],<br>
>> UNIT["degree",0.0174532925199433,<br>
>> AUTHORITY["EPSG","9108"]],<br>
>> AUTHORITY["EPSG","4326"]],<br>
>> PROJECTION["Transverse_Mercator"],<br>
>> PARAMETER["latitude_of_origin",0],<br>
>> PARAMETER["central_meridian",-117],<br>
>> PARAMETER["scale_factor",0.9996],<br>
>> PARAMETER["false_easting",500000],<br>
>> PARAMETER["false_northing",0],<br>
>> UNIT["Meter",1],<br>
>> EXTENSION["PROJ4","+proj=utm +zone=11 +datum=WGS84 +wktext"]]<br>
>> <br>
>> When passing proj.4 strings to GDAL utilities which take<br>
>> PROJ.4 as input you can include the +wktext option to force<br>
>> literal inclusion of the PROJ.4 string. For projections<br>
>> completely not supported by GDAL you will need to create<br>
>> WKT with some sort of fake projection (perhaps just use<br>
>> the above and update the EXTENSION[] portion.<br>
>> <br>
> I tried this a few months ago for another unsupported projection in GDAL with <br>
no luck. Doesn't work here either. Quote from Evan Rouault:<br>
> <br>
> "+wktext cannot help when OSR doesn't recognize the projection. It only helps <br>
> to keep the extra options that OSR doesn't handle by itself."<br>
> <br>
> So, if GDAL doesn't support ob_tran, +wktext won't help.<br>
> <br>
> -----<br>
> William Kyngesburye <kyngchaos*at*kyngchaos*dot*com><br>
> <a href="http://www.kyngchaos.com/" target="_blank">http://www.kyngchaos.com/</a><br>
> <br>
> First Pogril: Why is life like sticking your head in a bucket filled with <br>
hyena offal?<br>
> Second Pogril: I don't know. Why IS life like sticking your head in a bucket <br>
filled with hyena offal?<br>
> First Pogril: I don't know either. Wretched, isn't it?<br>
> <br>
> -HitchHiker's Guide to the Galaxy<br>
> <br>
> <br>
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-----<br>
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com><br>
<a href="http://www.kyngchaos.com/" target="_blank">http://www.kyngchaos.com/</a><br>
<br>
All generalizations are dangerous, even this one.<br>
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</tt></pre>
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