i.rectify2

[Gerald I. Evenden]

>Date: Wed, 05 Jan 1994 11:07:19 +0100
>From: olthof at ecn.nl (H. Olthof)
>Subject: i.rectify2
>
>Hello  all,
>
>We have rasterdata in lat-lon which cover a large part of Europe (From
>Scandinavia to South-Europe; from the UK to east Russia). We need these
>data in a mapset with lcc coordinates.  I rectified the maps with
>i.rectify2 (3rd order). I edited the POINTS-file for which I calculated
>the lcc coordinates for 15 points,distributed evenly over the area,
>exactly with m.proj.  The results are, however too inaccurate
>(Especially in the corners: the British isles, the Greek islands and
>southern Italy). Now my question:  Has anyone got a solution to
>increase the accuracy?  It is a pitty that r.in.ll is not made for the
>other projections, but only for UTM.
>
>--------------------------------------------
>ps. proj.info:
>
>name: Lambert Conformal Conic
>proj: lcc
>ellps: international
>a: 6378388.0000000000
>es: 0.0067226700
>lat_0: 52.0000000000
>lon_0: 6.0000000000
>lat_1: 33.0000000000
>lat_2: 70.0000000000
>------------------------------------------------
>
>Thanks, Harm olthof

I am jumping into the this only as the author of proj itself and not
the value added GRASS versions referred to here.

I do not understand the problems claimed for accuracy.  Lcc is
a closed form computation and thus is hardware precision limited while
TM (and UTM) is inherently less accruate because it is based upon
truncated approximation series (but still good to mm).

Please specify the details as to your accuracy claims.  What are you
comparing to?  Do you have a set of coodinates that you could send
that illustrate your problem?

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