Issue with ogrInfo

Dear all, I'm having the following issue when trying to read a
topographical json file:
The file is here
https://github.com/kjhealy/uk-elections/blob/master/maps/topo_wpc.json
uk.map <- readOGR(dsn = "maps/topo_wpc.json", layer = "wpc")
Error in ogrInfo(dsn = dsn, layer = layer, encoding = encoding,
use_iconv = use_iconv,  :
  Cannot open file
traceback()
5: .Call("ogrInfo", as.character(dsn), as.character(layer), PACKAGE = "rgdal")
4: ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv = use_iconv,
       swapAxisOrder = swapAxisOrder, require_geomType = require_geomType)
3: withCallingHandlers(expr, message = function(c)
invokeRestart("muffleMessage"))
2: suppressMessages(ogr_info <- ogrInfo(dsn = dsn, layer = layer,
       encoding = encoding, use_iconv = use_iconv, swapAxisOrder =
swapAxisOrder,
       require_geomType = require_geomType))
1: readOGR(dsn = "maps/topo_wpc.json", layer = "wpc")
sessionInfo()
R version 3.2.0 Patched (2015-04-19 r68207)
Platform: x86_64-apple-darwin10.8.0 (64-bit)
Running under: OS X 10.8.5 (Mountain Lion)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] rgdal_0.9-2 sp_1.1-0

loaded via a namespace (and not attached):
 [1] MASS_7.3-40      colorspace_1.2-6 scales_0.2.4     plyr_1.8.1
 [5] tools_3.2.0      gtable_0.1.2     reshape2_1.4.1   Rcpp_0.11.5
 [9] ggplot2_1.0.1    grid_3.2.0       stringr_0.6.2    digest_0.6.8
[13] proto_0.3-10     munsell_0.4.2    lattice_0.20-31

Dear all, I'm having the following issue when trying to read a
topographical json file:
The file is not recognised by OGR either, so is probably not conforming to 
geojson expectations. It declares itself as HTML, but within github puts 
boundaries on a map background, so I think the file is trying to do much 
more than simply represent Welsh parliamentary constituencies.

Roger
The file is here
https://github.com/kjhealy/uk-elections/blob/master/maps/topo_wpc.json

uk.map <- readOGR(dsn = "maps/topo_wpc.json", layer = "wpc")
Error in ogrInfo(dsn = dsn, layer = layer, encoding = encoding,
use_iconv = use_iconv,  :
 Cannot open file

traceback()
5: .Call("ogrInfo", as.character(dsn), as.character(layer), PACKAGE = "rgdal")
4: ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv = use_iconv,
      swapAxisOrder = swapAxisOrder, require_geomType = require_geomType)
3: withCallingHandlers(expr, message = function(c)
invokeRestart("muffleMessage"))
2: suppressMessages(ogr_info <- ogrInfo(dsn = dsn, layer = layer,
      encoding = encoding, use_iconv = use_iconv, swapAxisOrder =
swapAxisOrder,
      require_geomType = require_geomType))
1: readOGR(dsn = "maps/topo_wpc.json", layer = "wpc")

sessionInfo()
R version 3.2.0 Patched (2015-04-19 r68207)
Platform: x86_64-apple-darwin10.8.0 (64-bit)
Running under: OS X 10.8.5 (Mountain Lion)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] rgdal_0.9-2 sp_1.1-0

loaded via a namespace (and not attached):
[1] MASS_7.3-40      colorspace_1.2-6 scales_0.2.4     plyr_1.8.1
[5] tools_3.2.0      gtable_0.1.2     reshape2_1.4.1   Rcpp_0.11.5
[9] ggplot2_1.0.1    grid_3.2.0       stringr_0.6.2    digest_0.6.8
[13] proto_0.3-10     munsell_0.4.2    lattice_0.20-31

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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
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)"

Barry
On Sun, May 10, 2015 at 6:12 PM, Barry Rowlingson

 Solution is usually "use gdal/ogr tools to convert to plain old
geojson (ogr2ogr)"
Actually that's a really stupid solution. If ogr2ogr can do it, you
need the support in the first place! Doh!

 You need a separate tool. Something here might help:

http://recology.info/2015/01/geojson-topojson-io/
Barry

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

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at r-project.org
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
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).

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, 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

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at r-project.org
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

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo

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

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at r-project.org
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

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at r-project.org
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