[QGIS-Developer] Shapefile not correctly shown in some areas

[Aurélie Tisson (BastaPrint)]

Thanks a lot Andrea, you found the reason! 
The extent was wrong, and if I calculate & write it correctly, the file works. 
(Basically, I calculated it on the GPS points themselves, and not on the interpolated points, and it makes a difference because I interpolate points "before any GPS info" or "after the last GPS point"). 





To answer to other suggestions: 
- indeed, writing the file again from QGIS saves the new file in the right format 
- the .dbf file was not fautly. I had the same symptoms with or without it, so I did not mention it / send it. 

- I write the shapefiles "by hand", using the ESRI norm, playing around with the Little Endian and Big Endian formats (why did they make it so complex?). 



Thanks again ! 
Aurélie 


----- Mail original -----

De: "Andrea Giudiceandrea via QGIS-Developer" <qgis-developer at lists.osgeo.org> 
À: qgis-developer at lists.osgeo.org 
Envoyé: Samedi 13 Janvier 2024 11:47:33 
Objet: Re: [QGIS-Developer] Shapefile not correctly shown in some areas 

Hi all, 


> Colin Sare-Soar colin.saresoar at terrashape.co.uk 
> Fri Jan 12 19:21:21 PST 2024 
> I cannot see the point numbers or any info. The table is blank. 

This is due to the fact the the .dbf sidecar file which stores the 
fields names and values has not been provided or has not been created at 
all. 


> Il 12/01/2024 17:11, Aurélie Tisson (BastaPrint) via QGIS-Developer 
ha scritto: 
> If my viewing area includes the point 1612, I see all 
> the points, well aligned, but I cannot click points 1613 and further. 
> If I zoom in, or if I move the area and the point 1612 is out of the 
> area, I see nothing anymore. 

It looks like this issue is due to the fact that the extent stored in 
the .shp and in the .shx files is incorrect. 

As you can see in the Layer Properties / Information dialog window, the 
extent stored for such layer is: 

645765.5000000000000000,6860847.0000000000000000 : 
645766.3750000000000000,6860852.0000000000000000 


The points with Feature ID from 0 to 34 and from 1613 to 2000 are 
outside such extent. 

As suggested by Richard, just exporting the layer in a new ESRI 
Shapefile layer will write the right extent in the .shp and .shx files 
and the issue will not occur using the new layer. 

While I guess there is an issue in the code used to create the ESRI 
Shapefile layer, which not correctly updates the extent of the created 
layer, I also see some issue in QGIS itself and or in the GDAL/OGR library: 

- QGIS should be less strict and also display the features outside the 
stored extent and or warn the user about the incorrect extent 
- the "Updade extent" functionality in the Layer Properties / Source 
dialog window seems not working, at least for ESRI Shapefile layers 
- the "Repair Shapefile" processing algorithm (based on GDAL/OGR 
functionality) doesn't repair the incorrect extent stored in the .shx file. 

Best regards. 

Andrea 
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