[Proj] Bad Mercator Projection string?

[Geoff Shipton]

Mikael,

 

Many thanks you could be right, I had noticed that the lat_ts parameter was
not present in any of the other "typical" Mercator Proj4 strings I came
across - I will give this a try and let you know.

 

Geoff

 

From: Mikael Rittri [mailto:Mikael.Rittri at carmenta.com] 
Sent: Thursday, July 19, 2012 10:41 AM
To: <geoff at tritonimaginginc.com>; PROJ.4 and general ProjectionsDiscussions
Cc: proj at lists.maptools.org; Howard Unkeles
Subject: Re: [Proj] Bad Mercator Projection string?

 


I don't know what the trouble is, but maybe GeoTIFF doesn't support Mercator
with

a lat_ts parameter (latitude of true scale). If so, you can try to use a
scale factor instead. 

 

That is, replace your

 

    +lat_ts=41.5

 

by

 

    +k_0=0.750058844766239

 

This will give you an equivalent definition, and maybe it will work better. 

 

Best regards,

 

Mikael Rittri

Carmenta

Sweden

http://www.carmenta.com


18 jul 2012 kl. 19:16 skrev "Geoff Shipton" <geoff at tritonimaginginc.com>:

Hello everyone,

 

We "inherited" this Proj4 string from a previous product - it has always
seemed to work but we are having problems using it with gdalwarp, the warped
.tif image looks valid but has errors in the TIF tags.  If anybody has any
idea what's wrong I would be grateful.  Comparing it with other Mercator
Proj4 strings it looks a bit simple.

 

Here's the string:

 

+proj=merc +datum=WGS84 +lon_0=0 +lat_ts=41.5 +x_0=0 +y_0=2000000

 

I am not a geodesist, be gentle.

 

Many thanks,

Geoff Shipton,
Triton Imaging Inc.
Customer Support.
Capitola CA.
geoff at tritonimaginginc.com

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