GeoRSS is a way of encoding location in RSS or Atom feeds.
OGR has support for GeoRSS reading and writing. Read support is only available if GDAL is built with expat library support
The driver supports RSS documents in RSS 2.0 or Atom 1.0 format.
It also supports the 3 ways of encoding location : GeoRSS simple, GeoRSS GML and W3C Geo (the later being deprecated).
The driver can read and write documents without location information as well.
The default datum for GeoRSS document is the WGS84 datum (EPSG:4326). Although that GeoRSS locations are encoded in latitude-longitude order in the XML file, all coordinates reported or expected by the driver are in longitude-latitude order. The longitude/latitude order used by OGR is meant for compatibility with most of the rest of OGR drivers and utilities. For locations encoded in GML, the driver will support the srsName attribute for describing other SRS.
Simple and GML encoding support the notion of a box as a geometry. This will be decoded as a rectangle (Polygon geometry) in OGR Simple Feature model.
A single layer is returned while reading a RSS document. Features are retrieved from the content of <item> (RSS document) or <entry> (Atom document) elements.
The content returned by OGR will be encoded in UTF-8, after the conversion from the encoding mentioned in the file header is.
If your GeoRSS file is not encoded in one of the previous encodings, it will not be parsed by the
GeoRSS driver. You may convert it into one of the supported encoding with the iconv utility
for example and change accordingly the encoding parameter value in the XML header.
When writing a GeoRSS file, the driver expects UTF-8 content to be passed in.
The driver will return elements found in the base schema of RSS channel or Atom feeds. It will also return extension elements, that are allowed in namespaces.
Attributes of first level elements will be exposed as fields.
Complex content (elements inside first level elements) will be returned as an XML blob.
When a same element is repeated, a number will be appended at the end of the attribute name for the repetitions. This is useful for the <category> element in RSS and Atom documents for example.
The following content :
<item>
<title>My tile</title>
<link>http://www.mylink.org</link>
<description>Cool description !</description>
<pubDate>Wed, 11 Jul 2007 15:39:21 GMT</pubDate>
<guid>http://www.mylink.org/2007/07/11</guid>
<category>Computer Science</category>
<category>Open Source Software</category>
<georss:point>49 2</georss:point>
<myns:name type="my_type">My Name</myns:name>
<myns:complexcontent>
<myns:subelement>Subelement</myns:subelement>
</myns:complexcontent>
</item>
will be interpreted in the OGR SF model as :
title (String) = My title link (String) = http://www.mylink.org description (String) = Cool description ! pubDate (DateTime) = 2007/07/11 15:39:21+00 guid (String) = http://www.mylink.org/2007/07/11 category (String) = Computer Science category2 (String) = Open Source Software myns_name (String) = My Name myns_name_type (String) = my_type myns_complexcontent (String) = <myns:subelement>Subelement</myns:subelement> POINT (2 49)
If the output file already exits, the writing will not occur. You have to delete the existing file first.
A layer that is created cannot be immediately read without closing and reopening the file. That is to say that a dataset is read-only or write-only in the same session.
Supported geometries :
The GeoRSS writer supports the following dataset creation options:
When translating from a source dataset, it may be necessary to rename the field names from the source dataset to the expected RSS or ATOM attribute names, such as <title>, <description>, etc... This can be done with a OGR VRT dataset, or by using the "-sql" option of the ogr2ogr utility (see RFC21: OGR SQL type cast and field name alias)
The driver supports reading and writing to files managed by VSI Virtual File System API, which include "regular" files, as well as files in the /vsizip/ (read-write) , /vsigzip/ (read-write) , /vsicurl/ (read-only) domains.
Writing to /dev/stdout or /vsistdout/ is also supported.
ogrinfo -ro -al input.xml
ogr2ogr -f GeoRSS output.xml input.xml "select link_href as link, title, content as description, author_name as author, id as guid from georss"
#!/usr/bin/python
import gdal
import ogr
import urllib2
url = 'http://earthquake.usgs.gov/eqcenter/catalogs/eqs7day-M5.xml'
content = None
try:
handle = urllib2.urlopen(url)
content = handle.read()
except urllib2.HTTPError, e:
print 'HTTP service for %s is down (HTTP Error: %d)' % (url, e.code)
except:
print 'HTTP service for %s is down.' %(url)
# Create in-memory file from the downloaded content
gdal.FileFromMemBuffer('/vsimem/temp', content)
ds = ogr.Open('/vsimem/temp')
lyr = ds.GetLayer(0)
feat = lyr.GetNextFeature()
while feat is not None:
print feat.GetFieldAsString('title') + ' ' + feat.GetGeometryRef().ExportToWkt()
feat.Destroy()
feat = lyr.GetNextFeature()
ds.Destroy()
# Free memory associated with the in-memory file
gdal.Unlink('/vsimem/temp')