<div class="gmail_quote">---------- Forwarded message ----------<br>From: "Matt Priour" <<a href="mailto:mpriour@kestrelcomputer.com">mpriour@kestrelcomputer.com</a>><br>Date: Sep 19, 2013 11:59 AM<br>Subject: Re: [GeoJSON] Fwd: data series, time series in GeoJSON<br>
To: "Matt McClure" <<a href="mailto:matthewlmcclure@gmail.com">matthewlmcclure@gmail.com</a>><br>Cc: <br><br type="attribution"><p dir="ltr">If you want extra dimensions in your crs then you should add them to the end. If you prepend coordinates with time values, no existing geojson parsers/readers are going to be able to properly represent those coordinates. They will take the first value as x and second value as y and may or may not do anything with 3rd or 4th coordinates.</p>
<div class="gmail_quote">On Sep 19, 2013 11:24 AM, "Matt McClure" <<a href="mailto:matthewlmcclure@gmail.com" target="_blank">matthewlmcclure@gmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Thanks, Tom. I hadn't found that conversation before.<br>
<br>
In that thread, Jerry Sievert came to the same LineString<br>
conclusion[1] that I did. And Sean Gilles countered that a collection<br>
of Points[2]. Enumerating each Point as JSON seems pretty verbose, but<br>
MultiPoint seems like a reasonable compromise that's not very<br>
different from LineString.<br>
<br>
Is there any precedent for using CRSs where the first two elements in<br>
a Position are not (easting, northing) or (latitude, longitude)? I'm<br>
unclear on whether the spec indicates that those MUST be the first two<br>
elements, or if a GeoJSON file MAY specify an alternative CRS that<br>
uses different kinds of values in the first two elements.<br>
<br>
[1]: <a href="http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000826.html" target="_blank">http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000826.html</a><br>
[2]: <a href="http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000825.html" target="_blank">http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000825.html</a><br>
<br>
On Thu, Sep 19, 2013 at 11:51 AM, Tom MacWright <<a href="mailto:tom@macwright.org" target="_blank">tom@macwright.org</a>> wrote:<br>
> There's a bit of a more recent conversation from last month[1] on the more<br>
> general case of 'values along a line', with a similar conclusion - it's not<br>
> an easy thing to implement for any general case and it's something that's<br>
> possible to do 'by convention' without a change to the standard.<br>
><br>
> [1]:<br>
> <a href="http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000821.html" target="_blank">http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2013-August/000821.html</a><br>
><br>
><br>
> On Thu, Sep 19, 2013 at 11:48 AM, Matt McClure <<a href="mailto:matthewlmcclure@gmail.com" target="_blank">matthewlmcclure@gmail.com</a>><br>
> wrote:<br>
>><br>
>> Hi,<br>
>><br>
>> I'm reading the GeoJSON spec as I'm working on a way to represent time<br>
>> series data. I've looked through the mailing list archives and I've<br>
>> found a conversation from October[1] and November 2011[2], and a<br>
>> rejected proposal on the wiki.[3]<br>
>><br>
>> Does section 3[4] allow arbitrary CRS values, or does the condition<br>
>> that "" disqualify all CRSs that would use dimensions other than one<br>
>> of the two examples in section 2.1.1.[5]?<br>
>><br>
>> I wonder if a time series representation would conform to the existing<br>
>> GeoJSON 1.0 spec using an alternative CRS. For example, using URNs as<br>
>> described in "Definition identifier URNs in OGC namespace"[6], I might<br>
>> construct a compound CRS and use it as follows:<br>
>><br>
>> {<br>
>> "crs": {<br>
>> "type": "name",<br>
>> "properties": {<br>
>> "name":<br>
>><br>
>> "urn:ogc:def:crs,dataType:OGC:1.1:time,crs:OGC:1.3:CRS84,verticalDatumType:OGC:1.0:geoidal"<br>
>> }<br>
>> },<br>
>> "type": "LineString",<br>
>> "coordinates": [<br>
>> [<time>, <lat>, <lng>, <alt>], [...], ...,<br>
>> ]<br>
>> }<br>
>><br>
>> Would an example like this conform to GeoJSON 1.0?<br>
>><br>
>> Best,<br>
>> Matt<br>
>><br>
>> [1]:<br>
>> <a href="http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2011-October/000597.html" target="_blank">http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2011-October/000597.html</a><br>
>> [2]:<br>
>> <a href="http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2011-November/000601.html" target="_blank">http://lists.geojson.org/htdig.cgi/geojson-geojson.org/2011-November/000601.html</a><br>
>> [3]: <a href="https://github.com/GeoJSONWG/geojson-spec/wiki/Data-Series-Proposal" target="_blank">https://github.com/GeoJSONWG/geojson-spec/wiki/Data-Series-Proposal</a><br>
>> [4]:<br>
>> <a href="http://www.geojson.org/geojson-spec.html#coordinate-reference-system-objects" target="_blank">http://www.geojson.org/geojson-spec.html#coordinate-reference-system-objects</a><br>
>> [5]: <a href="http://www.geojson.org/geojson-spec.html#positions" target="_blank">http://www.geojson.org/geojson-spec.html#positions</a><br>
>> [6]: <a href="http://portal.opengeospatial.org/files/?artifact_id=24045" target="_blank">http://portal.opengeospatial.org/files/?artifact_id=24045</a><br>
>><br>
>><br>
>> --<br>
>> Matt McClure<br>
>> <a href="http://matthewlmcclure.com" target="_blank">http://matthewlmcclure.com</a><br>
>> <a href="http://www.mapmyfitness.com/profile/matthewlmcclure" target="_blank">http://www.mapmyfitness.com/profile/matthewlmcclure</a><br>
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><br>
><br>
><br>
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<br>
<br>
<br>
--<br>
Matt McClure<br>
<a href="http://matthewlmcclure.com" target="_blank">http://matthewlmcclure.com</a><br>
<a href="http://www.mapmyfitness.com/profile/matthewlmcclure" target="_blank">http://www.mapmyfitness.com/profile/matthewlmcclure</a><br>
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