[GeoJSON] Fwd: data series, time series in GeoJSON

Matt McClure matthewlmcclure at gmail.com
Thu Sep 19 09:24:07 PDT 2013


Thanks, Tom. I hadn't found that conversation before.

In that thread, Jerry Sievert came to the same LineString
conclusion[1] that I did. And Sean Gilles countered that a collection
of Points[2]. Enumerating each Point as JSON seems pretty verbose, but
MultiPoint seems like a reasonable compromise that's not very
different from LineString.

Is there any precedent for using CRSs where the first two elements in
a Position are not (easting, northing) or (latitude, longitude)? I'm
unclear on whether the spec indicates that those MUST be the first two
elements, or if a GeoJSON file MAY specify an alternative CRS that
uses different kinds of values in the first two elements.

[1]: http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000826.html
[2]: http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000825.html

On Thu, Sep 19, 2013 at 11:51 AM, Tom MacWright <tom at macwright.org> wrote:
> There's a bit of a more recent conversation from last month[1] on the more
> general case of 'values along a line', with a similar conclusion - it's not
> an easy thing to implement for any general case and it's something that's
> possible to do 'by convention' without a change to the standard.
>
> [1]:
> http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000821.html
>
>
> On Thu, Sep 19, 2013 at 11:48 AM, Matt McClure <matthewlmcclure at gmail.com>
> wrote:
>>
>> Hi,
>>
>> I'm reading the GeoJSON spec as I'm working on a way to represent time
>> series data. I've looked through the mailing list archives and I've
>> found a conversation from October[1] and November 2011[2], and a
>> rejected proposal on the wiki.[3]
>>
>> Does section 3[4] allow arbitrary CRS values, or does the condition
>> that "" disqualify all CRSs that would use dimensions other than one
>> of the two examples in section 2.1.1.[5]?
>>
>> I wonder if a time series representation would conform to the existing
>> GeoJSON 1.0 spec using an alternative CRS. For example, using URNs as
>> described in "Definition identifier URNs in OGC namespace"[6], I might
>> construct a compound CRS and use it as follows:
>>
>>     {
>>       "crs": {
>>         "type": "name",
>>         "properties": {
>>           "name":
>>
>> "urn:ogc:def:crs,dataType:OGC:1.1:time,crs:OGC:1.3:CRS84,verticalDatumType:OGC:1.0:geoidal"
>>         }
>>       },
>>       "type": "LineString",
>>       "coordinates": [
>>         [<time>, <lat>, <lng>, <alt>], [...], ...,
>>       ]
>>     }
>>
>> Would an example like this conform to GeoJSON 1.0?
>>
>> Best,
>> Matt
>>
>> [1]:
>> http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2011-October/000597.html
>> [2]:
>> http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2011-November/000601.html
>> [3]: https://github.com/GeoJSONWG/geojson-spec/wiki/Data-Series-Proposal
>> [4]:
>> http://www.geojson.org/geojson-spec.html#coordinate-reference-system-objects
>> [5]: http://www.geojson.org/geojson-spec.html#positions
>> [6]: http://portal.opengeospatial.org/files/?artifact_id=24045
>>
>>
>> --
>> Matt McClure
>> http://matthewlmcclure.com
>> http://www.mapmyfitness.com/profile/matthewlmcclure
>> _______________________________________________
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>> GeoJSON at lists.geojson.org
>> http://lists.geojson.org/listinfo.cgi/geojson-geojson.org
>
>
>
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>



-- 
Matt McClure
http://matthewlmcclure.com
http://www.mapmyfitness.com/profile/matthewlmcclure



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