[Freegis-list] FW: [ogdidev] Various Developments
Tue, 19 Sep 2000 09:45:03 -0700
From: Frank Warmerdam [mailto:firstname.lastname@example.org]
Sent: Tuesday, September 19, 2000 9:58 AM
Subject: [ogdidev] Various Developments
I thought I should give people heads up of a few things I have been working
o I have incorporated support in GDAL (http://www.remotesensing.org/gdal)
reading OGDI raster data. The work is preliminary, but it makes
use of ecs_SetRegion() to read back overview data when requested by the
This means that OpenEV (http://openev.sourceforge.net) can now be used as
an OGDI raster viewer. OpenEV understands that the OGDI raster source can
produce overviews at any level efficiently (well more efficiently than
loading full-res data into the application, and downsampling there). It
takes full advantage of this.
o I have implemented a simple OGDI driver for GDAL, so that I can access
any GDAL supported raster format from an OGDI enabled application. I
did this because I didn't think that any of the free OGDI drivers were
likely to generate overviews of rasters efficiently. The GDAL driver
do so, if the underlying file has pre-built overviews. GDAL includes
utilities for generating overviews for a variety of raster formats in
associated GeoTIFF files.
o Amoung other things, the above implementation include implementation of
a PROJ.4 to OpenGIS Well Known Text projection translation module. Code
to translate from OGC Well Known Text to PROJ.4 format was implmented
o Daniel Morissette has implemented read support for OGDI vectors within my
OGR library (a subtree of GDAL). In theory this means that OGR enabled
applications can read OGDI vector sources. Daniel also recently upgraded
the popular UMN MapServer to use OGR as one source of vector data.
can also use OGR to read vectors. While performance accessing vectors in
MapServer through OGR and OGDI layers may not be great, it is an
proof-of-concept of the technology.
I must stress that my recent work on OGDI <--> GDAL compatibility is
preliminary. It is a proof of concept. I haven't bundled binaries of any
of this, but the source is all in CVS. If anyone is interested in using
of these capabilities they can contact me for further details on what was
and how to get access to the code.
When (if?) I get binaries of OpenEV with OGDI support built on Windows (my
work has mostly been on Linux) I will make an announement here.
Both the work that I did, and the work that Daniel did are somewhat limited
by our ongoing problem with identifying layers available from an OGDI
automatically. We made it possible for a user who knows what layers they
to get access to them, but it is not generally possible at this time to get
list of available layers from a data source since there hasn't yet been any
standardization of how to do this as has been discussed at length here, and
elsewhere in the past.
I set the clouds in motion - turn up | Frank Warmerdam, email@example.com
light and sound - activate the windows | http://members.home.com/warmerda
and watch the world go round - Rush | Geospatial Programmer for Rent