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1500 questions
17
votes
2 answers
QGIS returns "Invalid Layer" message when trying to add PostGIS view?
I'm new to Postgis and QGIS. I created a view defined as
CREATE OR REPLACE VIEW pupr.vstudentmuni AS
SELECT m.id AS munid, m.name AS muname, m.geom, s.code,
(s.name::text || ' '::text) || s.lastname::text AS fullname
FROM pupr.municipio m,…
ufeliciano
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17
votes
5 answers
Seeking algorithm to place maximum number of points within constrained area at minimum spacing?
I have a polygon layer that describes a constraint; I wish to add points within this area. I want to add as many points as possible, but they must have a minimum spacing between them. Is it possible to do this with GIS?
To clarify, it would be…
Matthew Snape
- 6,127
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17
votes
6 answers
Converting between Esri Geometry and WKT using ArcObjects?
It seems like there is no means of converting an ArcObjects geometry to the Well-Known Text representation (and vice versa) in ArcGIS ArcObjects API. The only thing I was able to find is conversion to WKB (the IWkb interface).
Is there a way to…
Petr Krebs
- 10,291
- 1
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- 33
17
votes
6 answers
Preparing CSV files for use in ArcGIS Desktop?
How do I prepare CSV files for use in ArcGIS Desktop.
I ask because I have some troubles using CSV files because ArcGIS attributes wrong field types to my columns and also misinterprets special characters such as á or ê.
I have read in the Esri…
Dspanes
- 1,401
- 5
- 17
- 22
17
votes
2 answers
Showing the number of currently selected layers in QGIS
Although this should seem to be very straightforward, I cannot find out how to see the number of layers I have currently selected in QGIS. For example, in the example below I want to see somewhere in the GUI the number 5, or be able to somehow…
Sytze
- 731
- 6
- 18
17
votes
3 answers
What's the difference between gdalwarp and gdal_merge for mosaicing
I wanted to merge around 20 dem tiffs each around 100MB, and I used gdalwarp (I know about virtual file option):
gdalwarp $(list_of_tiffs) merged.tiff
However this command took very long time, and after some 15min it was processing 5th image from…
zetah
- 843
- 2
- 10
- 25
17
votes
3 answers
How to determine the date of the Bing imagery for an area?
Is it possible to determine how current the Bing imagery for a certain area is? I've checked the community blog and searched through the monthly updates, but I could not find my study area.
I found posts where they mentioned updating the imagery…
Cindy Jayakumar
- 4,045
- 7
- 39
- 75
17
votes
1 answer
Getting area / perimeter / length while digitizing
Is it possible in QGIS to see the area / perimeter of a shape or the length of a line while digitizing (not just after finishing it)?
I know, I can use the Advanced Digitizing Panel to get the coordinates, angles and length but not the area /…
MartinMap
- 8,262
- 7
- 50
- 114
17
votes
2 answers
Creating CSV with geometry as WKT in QGIS (with choosing field delimiter)
Is there a way to choose the field delimiter when exporting a CSV with geometry as wkt in QGIS?
I have a shapefile with donut holes and I'd like to export it as a CSV. It's for a partner whose DB doesn't support spatial data.
I followed Greg…
fgcarto
- 1,524
- 3
- 17
- 27
17
votes
1 answer
Rubbersheeting in GRASS?
We are in the process of getting our property boundaries corrected and a side effect of this is that we need to move any assets that have been drawn relative to the property boundaries, so they are still inline correctly.
The company that does the…
Nathan W
- 34,706
- 5
- 97
- 148
17
votes
2 answers
Seting 0 values in GeoTIFF to nodata using GDAL?
Is there a way to set all the 0 value pixels on a raster to nodata using GDAL?
I would like to use fillnodata to fill some holes, but holes are set to 0, so I need to delete them first
Andrea Ghensi
- 173
- 1
- 1
- 4
17
votes
4 answers
Buffering in PyQGIS
I'm looking for some examples to do simple python scripts in QGIS. How would I do a buffer analysis on a dataset?
I can't seem to find much in the manual and QGIS python that quite matches the ESRI documentation.
GIS Danny
- 733
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- 7
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17
votes
1 answer
Using Elseif Conditional Statement in QGIS Field Calculator?
I am trying to write an ELSEIF conditional statement in QGIS Field Calculator (version 1.8.0). I have used an example I found online:
CASE WHEN val < 0 THEN 'negative'
WHEN val = 0 THEN "neutral'
ELSE 'positive'
END
I modified the statement as…
Ryan Garnett
- 9,479
- 8
- 61
- 106
17
votes
2 answers
When not to create spatial index?
As I realized once again connected with this answer to Joining attributes by location using QGIS, creating a spatial index can result in huge performance improvements.
However, I was wondering why spatial indexes are not created as a default in GIS…
Babel
- 71,072
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- 208
17
votes
2 answers
Is there a standard data model for storing traffic volumes, layout, lanes, timing and phasing information?
I am at a crossroads where I want to store more than a scenarios worth of project data from a Synchro study, but do not want to keep this data in a series of text files. The data output by Synchro is standardized to a tab delimeted text file. The…
Michael Markieta
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- 36
- 65