[R-sig-Geo] Issue with ogrInfo

[Roger Bivand]

On Mon, 11 May 2015, Barry Rowlingson wrote:

> If you go far enough into the file (which appears to be without line
> breaks, so somewhere on line 1... You'll see:
>
> "arcs":[[[7533,1255],[-1,8],[0,4],[2,3],[-1,8],[2,2],[-2,2],[-1,0],[-1,1] .....
>
> which I think is the geometry (arcs have a start point and then x-y deltas).

Support for geometries like these may be coming to OGR, I think curves 
were also discussed. Using the converter here seems the best way forward.

Roger

>
> I can read this file if I first convert to geojson using the command
> line converter:
>
> $ topojson-geojson topo_wpc.json
>
> which gives me wpc.json, and then in R:
>
> > d=readOGR("./wpc.json","OGRGeoJSON")
> OGR data source with driver: GeoJSON
> Source: "./wpc.json", layer: "OGRGeoJSON"
> with 632 features and 3 fields
> Feature type: wkbPolygon with 2 dimensions
>
> Hmmmm
>
> Barry
>
>
>
>
> On Sun, May 10, 2015 at 6:38 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
>> On Sun, 10 May 2015, Barry Rowlingson wrote:
>>
>>> On Sun, May 10, 2015 at 4:31 PM, Daniel Marcelino <dmarcelino at live.com>
>>> wrote:
>>>>
>>>> Dear all, I'm having the following issue when trying to read a
>>>> topographical json file:
>>>
>>>
>>> That's a **topological**  (not topographical) geojson file. Instead
>>> of recording each polygon separately, and thus duplicating common
>>> boundaries, a topojson file stores all the line segments once, and
>>> then defines polygons as which sequence of line segments draws the
>>> polygon.
>>>
>>> I'm guessing your ogr library doesn't have topojson support. Does the
>>> output of ogrDrivers() agree with me?
>>>
>>> Solution is usually "use gdal/ogr tools to convert to plain old
>>> geojson (ogr2ogr)"
>>
>>
>> Right, but while the geojson driver does read topojson from 1.11, ogrinfo
>> says no-go. On inspecting the file, it appears only to contain lost of links
>> to other stuff and no geometries that I (or OGR) recognise. The geometries
>> must be hidden in one of the links, but are not exposed.
>>
>> Roger
>>
>>>
>>>
>>> Barry
>>>
>>> _______________________________________________
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>>>
>>
>> --
>> Roger Bivand
>> Department of Economics, Norwegian School of Economics,
>> Helleveien 30, N-5045 Bergen, Norway.
>> voice: +47 55 95 93 55; fax +47 55 95 91 00
>> e-mail: Roger.Bivand at nhh.no
>>
>> _______________________________________________
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>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 91 00
e-mail: Roger.Bivand at nhh.no