[gdal-dev] OGR Field Types?

[Stefan Keller]

2015-05-22 0:53 GMT+02:00 Even Rouault <even.rouault at spatialys.com>:
...
>> * "Easting","Northing"
> X,Y or Geometry(X), Geometry(Y) or Point(X),Point(Y) would perhaps be easier
> to get. I don't know.

So let's propose Point(X),Point(Y) or PointX,PointY.

-S.


2015-05-22 0:53 GMT+02:00 Even Rouault <even.rouault at spatialys.com>:
> Le vendredi 22 mai 2015 00:33:43, Stefan Keller a écrit :
>> 2015-05-21 23:34 GMT+02:00 Even Rouault <even.rouault at spatialys.com>:
>> ...
>>
>> >> 4. "Geometry(Easting)","Geometry(Northing)"
>> >
>> > For points only I guess?
>>
>> Yes.
>>
>> >> 5. "Geometry" -- encoded in WKT; having subtype values WKT (default),
>> >> Point, LineString, Polygon.
>> >
>> > "WKT" is not really consistant with Point,LineString,Polygon since the
>> > later would be expressed as WKT I guess. So perhaps WKT, WKT(Point),
>> > WKT(LineString), WKT(Polygon) ?
>>
>> Right, d'accord. So, let's introduce following two geometry types:
>> * "Easting","Northing"
> X,Y or Geometry(X), Geometry(Y) or Point(X),Point(Y) would perhaps be easier
> to get. I don't know.
>> * WKT, WKT(Point), WKT(LineString), WKT(Polygon)
>>
>> There are additional restricions to these geometry types:
>> * "Easting","Northing" must co-occur and should be neighboring columns
>> (in either order).
> I guess most people would do that, but I don't see a strong rationale to
> impose neighboring coumns
>> * if WKT is given, all rows are expected to contain the same geometry type.
> For generic WKT, all geometry types should be possible (as currently). Only
> for WKT(xxxx), geometries should be restricted to the specified type.
>> * There's only one geometry column per .csvt, namely either
>> <<"Easting","Northing">> or <<WKT>>.
> Kind of makes sense for Easting,Northing. But for WKT columns I don't see a
> reason for such a restriction. Actually there's already a
> secret/undocumented/debug mode in the CSV driver to read multiple geometry
> columns (I won't reveal it unless I'm tortured, but you can look at the code).
> This was mostly useful at the first stages when developing RFC 41.
>
>>
>> OK?
>
> Not sure what kind of committment would be expected if I say "OK", so I'll
> abstain ;-)
>
>>
>> --S.
>>
>> 2015-05-21 23:34 GMT+02:00 Even Rouault <even.rouault at spatialys.com>:
>> > Le jeudi 21 mai 2015 23:17:26, Stefan Keller a écrit :
>> >> Hi Even
>> >>
>> >> I just see some type mod and subtype definitions for .csvt files in
>> >> the CSV docs [1] :
>> >> <<
>> >> In a single line the types for each column have to be listed with
>> >> double quotes and be comma separated (e.g., "Integer","String"). It is
>> >> also possible to specify explicitly the width and precision of each
>> >> column, e.g. "Integer(5)","Real(10.7)","String(15)". The driver will
>> >> then use these types as specified for the csv columns. Starting with
>> >> GDAL 2.0, subtypes can be passed between parenthesis, such as
>> >> "Integer(Boolean)", "Integer(Int16)" and "Real(Float32)"
>> >> <<
>> >>
>> >> Following questions and suggestions about .csvt:
>> >> 1. Do type names really have to be in double quotes?
>> >
>> > No
>> >
>> >> 2. Is the separator always comma or can it also be a semicolon?
>> >
>> > Yes, always comma
>> >
>> >> 3. What about a Geometry type with subtypes? I suggest to add
>> >> 4. "Geometry(Easting)","Geometry(Northing)"
>> >
>> > For points only I guess? Well you can build points with a OGR VRT from 2
>> > CSV columns. I might perhaps add in some time an open option to specify
>> > the columns for the easting/longitude and northing/latitude.
>> >
>> >> 5. "Geometry" -- encoded in WKT; having subtype values WKT (default),
>> >> Point, LineString, Polygon.
>> >
>> > "WKT" is not really consistant with Point,LineString,Polygon since the
>> > later would be expressed as WKT I guess. So perhaps WKT, WKT(Point),
>> > WKT(LineString), WKT(Polygon) ?
>> >
>> >> What do you think?
>> >> This could also make QGIS "Add Delimited Text Layer..." even better.
>> >>
>> >> --S.
>> >>
>> >> [1] http://www.gdal.org/drv_csv.html
>> >>
>> >> 2015-04-29 22:57 GMT+02:00 Stefan Keller <sfkeller at gmail.com>:
>> >> > Salut Even,
>> >> >
>> >> > Merci!
>> >> >
>> >> > 2015-04-29 20:35 GMT+02:00 Even Rouault <even.rouault at spatialys.com>:
>> >> >> Stefan
>> >> >>
>> >> >>> Questions:
>> >> >>> 1. How is 'binary' encoded? E.g. when defining binary in a CSV file,
>> >> >>> how is it encoded? Hex?
>> >> >>
>> >> >> There's no support in the CSV driver for binary data
>> >> >>
>> >> >>> 2. Can a field in a CSV input files have a IntegerList or a Binary?
>> >> >>
>> >> >> No. Well on writing, the IntegerList will be serialized as a string.
>> >> >> But not recognized as IntegerList on reading
>> >> >>
>> >> >>> 3. What is the value delimiter in a field of type IntegerList,
>> >> >>> Integer64List, RealList, StringList?
>> >> >>
>> >> >> The default serializatoin will be
>> >> >> (number_of_elements:val1,val2,...,valn), but currently it is
>> >> >> truncated to 80 chracters
>> >> >>
>> >> >>> 4. "Boolean, Int16, Float32" are mentioned as subtypes. Are there
>> >> >>> more subtypes?
>> >> >>
>> >> >> Not currently. See
>> >> >> https://trac.osgeo.org/gdal/wiki/rfc50_ogr_field_subtype
>> >> >>
>> >> >> Even
>> >> >>
>> >> >> --
>> >> >> Spatialys - Geospatial professional services
>> >> >> http://www.spatialys.com
>> >
>> > --
>> > Spatialys - Geospatial professional services
>> > http://www.spatialys.com
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com