Date: Wed, 05 Jan 1994 11:07:19 +0100
From: olthof@ecn.nl (H. Olthof)
Subject: i.rectify2Hello 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@charon.er.usgs.gov
voice: (508)563-6766 Postal: P.O. Box 1027
fax: (508)457-2310 N.Falmouth, MA 02556-1027