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

[Richard Duivenvoorde]

Hi Aurélie,

I can reproduce your findings.

I'm not an expert on shapefile format, but how do you create the shapefile?

Is it possible that the shx file is not in line anymore with the shp/dbf file?
If I'm correct the shx is the shape-index file, probably used by QGIS or other tools to quickly find points within a bbox etc.
See: https://gis.stackexchange.com/questions/294868/explaining-difference-between-shx-and-shp-files-of-shapefile

I think your shp and shx file are not in line with each other anymore.

As a test, I exported your shapefile in QGIS to another shp file, and THAT copy works fine.

So I think you have to dive into your shp file creation software, and make sure it also update the shx OR (re)create the shx after creating shp and dbf

Regards & hth,

Richard Duivenvoorde

On 1/12/24 17:11, Aurélie Tisson (BastaPrint) via QGIS-Developer wrote:
> Hello,
> To make things short, I have a device which gathers data in the fields (hundreds of data per second), and gets the position through a GPS (every second).
> Between 2 GPS positions, I triangulate the positions, so the points are aligned.
> Sometimes, the device "writes" the data so it spends some time doing so, and it does not gather anything, so I have a "hole".
> 
> Then, to visualize the data, I create a Shapefile, only with Points.
> 
> In one Shapefile, I had some strange points: points that appear on the map, but are not clickable and disappear when I zoom in too much. I attach the files ; they can be downloaded here, too:   https://www.grosfichiers.com/sjNC3yx7Kvi
> 
> For instance, in the file I join, the position number 1613 and further are problematic. 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.
> 
> The code to generate the Shapefile has a systematic approach: it takes the points one after the other, and writes their position by incrementing the values. So I suspect there is no bug.
> In a previous test, the same problem occured BEFORE point 1217 : I could only see the first points if the area included point 1217.
> 
> Questions:
> - can anyone try to see my shapefile and confirm the problem?
> - does this bug ring a bell to anyone?
> - what may be the problem?
> 
> Thank you very much!
> My versions are detailled below. I just updated to the LTR to try to solve the problem, but the bug exists with the 3.22.7-Białowieża  and 3.28.14-Firenze versions.
> 
> 
> Aurélie
> 
> 
> Version de QGIS
> 
> 	
> 
> 3.28.14-Firenze
> 
> 	
> 
> Révision du code
> 
> 	
> 
> b09131c512 <https://github.com/qgis/QGIS/commit/b09131c512>
> 
> Version de Qt
> 
> 	
> 
> 5.15.3
> 
> Version de Python
> 
> 	
> 
> 3.9.5
> 
> Version de GDAL/OGR
> 
> 	
> 
> 3.8.2
> 
> Version de Proj
> 
> 	
> 
> 9.3.1
> 
> Version de la base de données du registre EPSG
> 
> 	
> 
> v10.098 (2023-11-24)
> 
> Version de GEOS
> 
> 	
> 
> 3.12.1-CAPI-1.18.1
> 
> Version de SQLite
> 
> 	
> 
> 3.41.1
> 
> Version de PDAL
> 
> 	
> 
> 2.6.0
> 
> Version du client PostgreSQL
> 
> 	
> 
> unknown
> 
> Version de SpatiaLite
> 
> 	
> 
> 5.1.0
> 
> Version de QWT
> 
> 	
> 
> 6.1.6
> 
> Version de QScintilla2
> 
> 	
> 
> 2.13.4
> 
> Version de l'OS
> 
> 	
> 
> Windows 10 Version 2009
> 
> 
> 	
> 	
> 	
> 
> Extensions Python actives
> 
> QGeoloGIS
> 
> 	
> 
> 1.9.0
> 
> db_manager
> 
> 	
> 
> 0.1.20
> 
> grassprovider
> 
> 	
> 
> 2.12.99
> 
> MetaSearch
> 
> 	
> 
> 0.3.6
> 
> processing
> 
> 	
> 
> 2.12.99
> 
> sagaprovider
> 
> 	
> 
> 2.12.99
> 
> 
> 
> ======= Previously  =========
> 
> Version de QGIS
> 
> 	
> 
> 3.22.7-Białowieża
> 
> 	
> 
> Révision du code
> 
> 	
> 
> 5a65627a <https://github.com/qgis/QGIS/commit/5a65627a>
> 
> Version de Qt
> 
> 	
> 
> 5.15.3
> 
> Version de Python
> 
> 	
> 
> 3.9.5
> 
> Version de GDAL/OGR
> 
> 	
> 
> 3.4.3
> 
> Version de Proj
> 
> 	
> 
> 9.0.0
> 
> Version de la base de données du registre EPSG
> 
> 	
> 
> v10.054 (2022-02-13)
> 
> Version de GEOS
> 
> 	
> 
> 3.10.2-CAPI-1.16.0
> 
> Version de SQLite
> 
> 	
> 
> 3.38.1
> 
> Version de PDAL
> 
> 	
> 
> 2.3.0
> 
> Version du client PostgreSQL
> 
> 	
> 
> 13.0
> 
> Version de SpatiaLite
> 
> 	
> 
> 5.0.1
> 
> Version de QWT
> 
> 	
> 
> 6.1.6
> 
> Version de QScintilla2
> 
> 	
> 
> 2.13.1
> 
> Version de l'OS
> 
> 	
> 
> Windows 10 Version 2009
> 
> 
> 	
> 	
> 	
> 
> 
> 	
> 
> 	
> 
> 	
> 
> 	
> 
> 	
> 
> 	
> 
> 
> 
> 
> 
> 
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