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

[Peter Hopfgartner]

Chris Hermansen wrote:
> Peter;
>
> The canonical description of DBase files seems to be
>
> http://www.clicketyclick.dk/databases/xbase/format/
>
>   
Well, first of all, I do not know which dBase version is targeted by ArcGIS.

Second, I doubt the exact values in 
http://www.clicketyclick.dk/databases/xbase/format/data_types.html#DATA_TYPES.

 From our tests, both dbase III and dBase IV can handle text fields <= 
254 characters (and not < 254).
Further, dBase III can handle numerics with <= 19 digits and not < 18 
digits. dBase IV limits this to <= 20 digits.

The above mentioned tool identifies ArcGIS generated files as dBase IV, 
in clear conflict on what is said in the above mentioned Wikipedia article.

Cheers,

Peter
> On Tue, 2009-12-01 at 17:28 +0100, Peter Hopfgartner wrote:
>   
>> 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
Via Johann Kravogl-Str. 2
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Email: peter.hopfgartner at r3-gis.com
Tel. : +39 0473 494949
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www  : http://www.r3-gis.com

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