[Qgis-user] vector layer only displays when zoomed out to layer extent

[Lee Eddington]

So for the first question I asked below, I was referring to your statement that "When you cross 360 degrees, some projections have difficulty dealing with that.”  My lines don’t technically cross 360 deg, but they cross 0 deg, as the data values for the line positions are all  > -360 and < 360 deg.  So they cross at 0 deg with values like -0.345, 33.00 to 0.231, 32.94.

I was able to save the densification layer to a file as you suggested, but when I do that the lines in the densified file will only display when the zoom is for the full extent of the layer like the original file.  Only if the densified lines are in a temporary scratch layer will they display at other zoom levels.

Regarding the other suggestion "It's likely a corrupt spatial index on the file. Try removing and recreating it.”.  I don’t know how to find, remove and recreate a corrupt spatial index.  Any instructions on how to do this would be appreciated.

Thanks,
Lee


> On Dec 17, 2019, at 1:54 PM, Nicolas Cadieux <nicolas.cadieux at archeotec.ca> wrote:
> 
> Hi,
> 
> Not sure for question one.  Have you tried creating a spatial index as others have suggested? When you run the densify tool, If you don't specify the name, the output will be a temporary layer. You should be able to do a save as for the layer.  Remember to close the temporary file after exporting it or else you will get that message.
> 
> Nicolas
> 
> On 2019-12-17 12:51 p.m., Lee Eddington wrote:
>> If my layer extent is > -360 and < 360 am I really crossing 360?  I’m crossing 0 from negative values to positive values.  Is that the same?
>> 
>> Also, regarding not being able to save the layer I created with densification, when I try to close QGIS it says I have a ’scratch’ layer that will be lost, which would be this layer created by densification.  How do you save a scratch layer?
>> 
>> Best,
>> Lee
>> 
>> 
>>> On Dec 16, 2019, at 7:43 PM, Nicolas Cadieux <nicolas.cadieux at archeotec.ca> wrote:
>>> 
>>> Hi,
>>> When you cross 360 degrees, some projections have difficulty dealing with that.  Try not crossing that or try splitting the shapes that cross it.
>>> Nicolas
>>> 
>>>> Le 16 déc. 2019 à 22:32, Lee Eddington <lee.w.eddington at gmail.com> a écrit :
>>>> 
>>>> I’m not sure that’s the reason as I have plenty of points in my lines.  Also, I saved the densified layer to disk, but the saved layer has the same display problem as the original layer.
>>>> 
>>>> Lee
>>>> 
>>>> 
>>>>> On Dec 16, 2019, at 8:35 AM, Nicolas Cadieux <nicolas.cadieux at archeotec.ca> wrote:
>>>>> 
>>>>> Hi,
>>>>> 
>>>>> If you have a very long straight line represented by only two point, reprojection operates only on those two points (called vertices or nodes).  The lines just represent a straight connections between two point.  The problem is that the earth is round (contrary to some popular belief :) and those long straight lines need to be bent depending on the projection being used.   Since reprojection and zooming only operates on vertices or nodes, densification adds nodes to the line giving more points to calculate and thus, less errors.
>>>>> Cheer!
>>>>> Nicolas
>>>>> 
>>>>> 
>>>>> 
>>>>>>> Le 16 déc. 2019 à 10:23, Lee Eddington <lee.w.eddington at gmail.com> a écrit :
>>>>>> Hi Nicolas,
>>>>>> 
>>>>>> Vector densification worked.  I went with the default 1 vertices to add and it created a new layer that now displays at any zoom level.  Can you explain why my original layer doesn’t display?
>>>>>> 
>>>>>> Thanks,
>>>>>> Lee
>>>>>> 
>>>>>> 
>>>>>>> On Dec 14, 2019, at 3:13 PM, Nicolas Cadieux <nicolas.cadieux at archeotec..ca> wrote:
>> .
>>