[osg-users] [vpb] Correct way to get texture data from USGS or any other source?

[Christian Schulte]

Hello,

how I found it ? Easy (LOL!), the EPSG:2238 is the official map 
projection for north of Florida and from the values in the file (Center 
( 1657500.330, 572499.510)) you can see (okay, I admit if you are used 
to look at this kind of data :-) ) that it is a distance in feet from a 
reference point. That is typical for a Mercantor or Lambert projection. 
In every case I would advise you to check in a converter what latitude 
and longitude you will obtain from the centre of the image and double 
check with google maps or equivalent that you find again the same point.
Because you can convert a lot of different projections to latitude and 
longitude, as the equations are nearly the same only the correction 
factors or the reference ellipsoid will change. So it will convert but 
you are not sure to be in the right place in the world...
For your information, the EPSG:3857 is a non officially recognized 
projection as it uses a sphere as earth reference and not a ellipsoid. 
Furthermore this projection system is centred on Equator/Greenwich so 
you may have in the United States an error up to 43 km in map 
projection, (nearly 21 km on the ground).

Regards,

Christian


Le 09/06/2015 23:15, Elias Tarasov a écrit :
> Hello!
>
>
> Christian Schulte wrote:
>> Hello!
>>
>> I totally agree with Sebastian. These data is surely geo-referenced, as
>> I myself often used in the past data from USGS. Locking at the metadata
>> you provided I would say that you are in an EPSG:2238 Lambert Conformal
>> Conic projection, which is the main projection system for north Florida.
>> You may try to specify to GDAL the source projection using this EPSG code.
>>
>> Regards,
>>
>> Christian
>>
> Yes, it worked! However, i dont understand how did you figure out that projection is 2238. No such a number is presented into metadata.
> For a test, i also used EPGS:3857 and it seems to work similar.
>
> Thanks a lot!
>
> Elias.
>
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-- 
SCHULTE Christian
Ingénieur Recherche
Responsable du Laboratoire de Simulation
ONERA - DCSD/PSEV
Département Commande des Systèmes et Dynamique du Vol
ONERA - Centre de Salon de Provence
BA 701
13661 SALON AIR Cedex - France
Tel :04.90.17.01.45