Lambert Azimuthal and 1st standard

Gerald I. Evenden gie at charon.er.usgs.gov
Tue May 2 09:08:05 EDT 1995


>Subject: Lambert Azimuthal and 1st standard
>Sender: grass-lists-owner at moon.cecer.army.mil
>To: grassu-list at max.cecer.army.mil
>Date: Mon, 1 May 95 17:32:38 MDT
>
>Good Afternoon,
>
>I am trying to get a LAEA projected image into grass. I have the laea PROJ file
>set up and can display the image but it is extremely scretched west to east.
>
>I am interested to know if I am specigying the right 1st standard parallel
>when asked for by the projection menu.

What "standard parallel?"  I do not recall any standard parallel for
Lambert Azimuthal Equal Area.

>Basically I have an OTTER image, with
>Center Lat = 44.4242
>Center Lon = -122.3086

Presumably lat_0 and lon_0 or point of tangency of projection plane.

>1st Standard Parallel = 45.8311 (upper latitude) is this correct ?

laea does not have a standard parallel.  Has someone mixed this up
with lcc or Lambert Conformal Conic?

>Also what is the standard ellipsoid that can be used with this projection
>clark66 or clark80 , what are people using for the best results.

It is not a matter of "best results," its a matter of datum.  Your area
appears to be in North America so it would either be NAD27's clrk66 or
NAD83's WGS80.

>The stretch in the image should be about 2:1 (east west:north south)

???

>Any suggestions
>
>Thanks
>
>Jeremy

I am certainly confused by your request.  This confusion may be
furthered by the software you are attempting to use and variation of
the forms of reference as compared to those that I use in the PROJ
system (upon which the aforementioned software *may* be dependent).  I
am also surprised by the use of an azimuthal projection for image
(presumably satellite) data.

Anyway, for Lambert Azimuthal Equal Area projection, there is nothing
that is normally termed "the standard parallel" nor "upper latitude."

Gerald (Jerry) I. Evenden   Internet: gie at charon.er.usgs.gov
voice: (508)563-6766          Postal: P.O. Box 1027
  fax: (508)457-2310                  N.Falmouth, MA 02556-1027



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