MAPS-L Archives

Maps-L: Map Librarians, etc.

MAPS-L@LISTSERV.UGA.EDU
Options: Use Forum View

Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
Coordinate transformation - please help!! (fwd)
From:
Johnnie Sutherland <[log in to unmask]>
Reply To:
Maps and Air Photo Systems Forum <[log in to unmask]>
Date:
Thu, 13 Jul 2000 13:47:33 -0400
Content-Type:
TEXT/PLAIN
Parts/Attachments:
TEXT/PLAIN (60 lines) 
---------- Forwarded message ----------
Date: Thu, 13 Jul 2000 18:46:08 +0200 (CEST)
From: Umberto Fracassi <[log in to unmask]>
To: [log in to unmask], [log in to unmask]
Cc: [log in to unmask], Gis-list <[log in to unmask]>
Subject: Coordinate transformation - please help!!

Hi all, and sincere apologies for cross-postings..

I am working on shapefiles representing contours of the Campo Imperatore
are (central Italy). They have been digitized at 1:10.000 by a regional
cartographic board (apparently from the IGM official cartography) in Italy
- using Gauss-Boaga projection...! It is basically a Transverse Mercator
projection, using the International 1924 spheroid and the Rome 1940 datum
- yes, I know, it's a very local projection style..

I imported these files in Erdas, and I was initially unaware and
ininformed they were digitized from maps in Gauss-Boaga. For a number of
practical reasons, I'd prefer to have all the material in UTM (using the
Inernational 1909 spheroid and the European ED 1950 datum).

Trouble is, when I reproject the dataset, numbers get quite out of place.
While northings appear to be realistic, I couldn't say the same for
Eastings. Gauss-Boaga has a false Eastings of 1.500.000m, and this is very
visible on the reprojection. Just an example for the upper left pixel
coords:

Gauss-Boaga Int 1924, Rome 1940
X       2403253         Y       4695060

UTM Int 1909, ED 1950, zone 33
X       909026          Y       4665704

The 909026 is the one that really doesn't fit.. From the 1:25.000 map of
the area this value should be some 400.000 m (ie. about 2.000.000 m less
than the Gauss-Boaga figure)..

Anybody any idea on the everlasting issue of coordinate conversion..?

Many thanls in advance for any suggestion - I've been wasting quite a bit
fo time so far with this rather basic detail..

Ciao,


Umberto Fracassi

---------------------------------------------------------------
Dip.to di Scienze della Terra
Universita' di Firenze
Via I. Nardi, 2
50132 Firenze
Italy

Tel:    +39-055-243486
Fax:    +39-055-241595
Email:  [log in to unmask]
WWW:    http://geosciences.org/umberto
---------------------------------------------------------------

ATOM RSS1 RSS2