Am 15.12.2010 16:47, schrieb Howard Butler:
On Dec 15, 2010, at 9:30 AM, Ari Jolma wrote:
On 12/15/2010 05:11 PM, Frank Broniewski wrote:
Hello Ari,
yes that is definitely helpful. But I still wonder if it might be
easier/quicker to use GeoJSON as a interchange format and tranform from geojson
to other formats than using OGRs internal structure. I already have some
convenience classes for creating GeoJSON structures in Python. I know there is
already a geojson python module [1], but onfortunately it doesn't deal with
projections afaik.
GDAL has support for GeoJSON too. And it seems to support projections.
GeoJSON explicitly supports projections, and OGR's implementation tries its
best to deal with them. GeoJSON's original intent is as a
slightly-more-up-to-date, Javascript-consumable interchange format. A better
WKT, if you will. With a light concept of features and feature collections.
It's a great way to interchange geometries and (sometimes) features between
softwares of the Python world, the Javascript world, and the PostGIS world.
There are some gotchas with GeoJSON as far as features are concerned though. A
GeoJSON feature object is essentially free-standing, and an array of them need
not have a common schema to describe the layout of all of the features in that
array. In practice, the features of an array typically have a common schema,
but this requirement is not enforced in any way. This property of GeoJSON can
cause some leakage in that respect.
ESRI's JSON output is not GeoJSON, and AFAIK there is no interchange capability
there.
Howard_______________________________________________
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Hello Howard,
thank you very much for your detailed answer. I know that GeoJSON
supports projections, the before mentioned python package (from Sean
Gillies and Matt Russel) doesn't: "Version 1.0 does not consider
coordinate systems." [1]
I am doing database based CAD to GIS conversions and therefore I was
looking for an easy to use interchange format. Having used GeoJSON
before with a number of OpenLayers Web applications, I know this format
well and the really pleasant way to create this format from a number of
different data sources. My only concern was actually if it wouldn't be
more efficient to use OGRs internal data format directly. But I will be
using GeoJSON as my transport format now. So I don't have to deal too
much with OGRs C-API which I don't understand very well. I am just a
geographer, not a programmer.
Luckily I won't have to deal with ESRIs data formats - apart from
Shapefiles of course :-)
Frank
[1] - http://trac.gispython.org/lab/wiki/PythonGeoInterface
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