[postgis-users] Length of Bigint, Double and Text fields

[Peter Hopfgartner]

Mark Cave-Ayland wrote:
> Peter Hopfgartner wrote:
>
>> Dear PostGIS devels,
>>
>> since we right in the middle of comparing interoperability of shape 
>> files between some FOSS programs and ArcGIS, we encoutered also the 
>> following:
>>
>> gvSIG chokes on the Bigint as produced by pgsql2shp. Looking at 
>> ArcGIs generated files, the max length for numbers is 19, compared to 
>> 20 for integers and 32 for floating points as in pgsql2shp. This 
>> seems to be confirmed by some Borland tools, when configured for 
>> dBase III+.
>>
>> Another limit seems to be that of text fields, that must be no longer 
>> then 254. This is the maximum as given by ArcGIS and by the Borland 
>> tool.
>>
>> Another point is Boolean: ArcGIS seems to not allow the creation of 
>> boolean fields and the Borland Tool ("Database Desktop") says that 
>> Booleans have a length of 1.
>>
>> Regards,
>>
>> Peter
>
> Hi Peter,
>
> You've brought up some interesting points here. Can you actually 
> clarify these changes with regard to parts of the official shapefile 
> spec, or have they been found purely through experimentation?
>
>
> ATB,
>
> Mark.
>
Hi Mark,

I do still have to figure out, if there are public specs for this. All 
I've found is, that attributes should be in data base files which are in 
dBase format 
(http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf). From the 
analysis of the file (and Wikipedia: 
http://en.wikipedia.org/wiki/Shapefile), it seems that this should be 
dBase III. I do not have any evidence that there is a public spec for 
dBase III.
So all we did is basically gather some experimental data, where ArcGIS 
and gvSIG are our references. The first, because ESRI introduced the 
shape file format and gvSIG, because it is the desktop environment that 
we encourage our customers to use. Anyway, we have an old 
Borland/Inprise tool ("Database Desktop") here for managing dBase files 
and used it for our tests.

Peter

-- 
 
Dott. Peter Hopfgartner
 
R3 GIS Srl - GmbH
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Email: peter.hopfgartner at r3-gis.com
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