June 2005
Beginner to intermediate
372 pages
10h 1m
English
Content preview from Web Mapping IllustratedBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Using Projections with Other Applications
MapServer is just one application of many that use PROJ.4
to help project coordinates. Two other utilities discussed elsewhere in
this book can use the power of PROJ.4 to project data/features into new
projections. This is often accomplished using a few command-line
options. The gdalwarp and ogr2ogr command-line tools (part of the GDAL/OGR
package hosted at http://gdal.org) allow
you to convert raster and vector data, respectively, between formats.
You can also specify a target spatial reference system using the
-t_srs option. For example, to
convert an image that is referenced to latitude/longitude coordinates,
into a Mercator projection, the following command might be used:
> gdalwarp -t_srs "+proj=merc +ellps=WGS84" in.tif out.tifThere is also an option, -s_srs, that allows you to specify the source
SRS. This is essential if the data you have isn't already encoded with
projection information.
Here is another example; it uses the ogr2ogr vector conversion utility to convert a
shapefile from one SRS to another. The source SRS is also supplied
because there was no projection information (or .prj file) supplied with the data.
> ogr2ogr -s_srs "+proj=latlong" -t_srs "+proj=merc +ellps=WGS84" city_merc.shp city_in.shpBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.