Questions tagged [geometry]
(1) abstract geometry; (2) storing geographic data in projected coordinates; (3) a generic ESRI term for vector features; a class for "geometry" objects.
339
questions with no upvoted or accepted answers
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805
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Change from LineString to MultiLineString when saving layer edits in QGIS
In QGIS, when a user creates a new single part line in an open editing session for a “Multi-Line” SpatiaLite dataset, the QGIS data type is initially a “LineString”. But, when the user commits the ...
- 967
5
votes
0
answers
721
views
QGIS geometry error:Hole lies outside shell
I am using QGIS 3.8 and I am using a layer from OSM of Tokyo city.
The layer is consisted from many polygons and I have tried to merge it but I got error.
This is how the original layer was look like:...
- 2,047
4
votes
0
answers
804
views
QGIS Convert Shapefile to MSSQL as geography type
I am using QGIS 3.16 and SQL Server 2019.
I have a shapefile loaded into the project. I have been able to successfully convert the Shapefile to a spatial dataset in SQL Server. My method for doing ...
4
votes
0
answers
2k
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how to orthogonalize building outlines
I'm looking for a way to orthogonalize building outlines which I've extracted from a high-res DEM. I'm using the FOSS GIS stack (QGIS, GRASS, SAGA, PostgrSQL, PostGIS) and can code in Python (or Java)....
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4
votes
1
answer
993
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How to offset/displace overlapping lines in a web map?
I have a dataset of points representing a To/From status - something like distribution centres and delivery addresses.
When the user clicks on a point I'd like to show the relationships between this ...
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3
votes
1
answer
114
views
How can I get the closest linestring in my database to the linestring drawn by some user, following a path?
I have to take a geometry drawn by an user and return the geometry in my database that represents the drawing. I tried in PostGIS
In my database I have a column 'way' with the geometry that I want to ...
3
votes
0
answers
320
views
High cost of geometry bitmap heap scan
I have a PostGIS database with tables osm_admin (with contains all administrative boundaries from osm data) and osm_landusages (with contains all landuse areas form osm - like forests, industrial/...
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3
votes
1
answer
337
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Optimising Large Spatial Queries in SQL
I'm sure similar answers have been given elsewhere but no matter what I have tried I am unable to optimise this query.
Details: TableA has 3.5mill records TableB Had 57000 records but I have ...
- 99
3
votes
0
answers
491
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Generate arc from projection coordinates
I have a mind to generate arc from given parameters:
start point coordinates
arcDistance
arcBearing
arcOrigin coordinates.
My concept is, calculate the end point of arc (function geo.sphere....
- 1,066
3
votes
0
answers
83
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Lines length plugin - QgsVectorLayer error
Several similar questions have already been made, but none of the is helping me.
I have a layer of polygons and I want to known the length of each line of each polygon. And based on the length I ...
- 43
3
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0
answers
750
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Calculate length of selected features in PyQGIS
I create a selection with getFeatures(QgsFeatureRequest()) and I want to calculate the length of the result which is a QgsFeatureIterator :
select = QgsExpression(" myexpression ")
selectedfeats = ...
- 1,097
3
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0
answers
2k
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What is geometry(4326), and can you do Cartesian calculations with unprojected ellipsoidal coordinates?
I know Geography(4326) is an unbounded, and unprojected, and covers the entire world with ellipsoidal coordinates. I get that the math on this system is done on a spheroid. I also get that with a ...
- 7,031
3
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274
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ST_ApproximateMedialAxis producing strange outputs
My problem is as follows: I have some lines (yellow), that I want to merge in one line if they are at a certain distance (blue, buffer), and after a long research I found this function from PostGIS/...
- 1,103
3
votes
1
answer
2k
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Removing vertex from Polygon geometry in OpenLayers 5
I could able to remove the recent modified vertex of a feature using removePoint method of modify interaction, as well as using deleteCondition event of modify interaction. However, that is not what I ...
- 619
3
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0
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1k
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How to plot geometry(MultiPolygon, 3044) QGIS based datatype in python
I have a table tb_regions in Postgresql having a column c_geometry which contains geometry(MultiPolygon, 3044) datatype from QGIS. I know how to retrieve data from Postgresql using pythons psycopg2 ...
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3
votes
0
answers
465
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Building footprint polygon simplification / generalisation
I'm looking for implementations of polygon simplification algorithms that preserve topology and overall rectilinearity. The input data is building footprints which often have squarish protrusions and ...
- 515
3
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0
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507
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Dissolve fails, geometry errors, and cleaning problems
I fairly new to GIS, and I'm having an issue with dissolving a vector. To start, I'm running QGIS 2.14.15 on Windows 7 Pro. When I try to dissolve the polygons it creates a blank shapefile. All of the ...
3
votes
0
answers
706
views
What does "Feature doesn't have a geometry" mean in QGIS?
When I open the .shp file and click on specfic item in the attribute table, in the canvas, it said "Feature doesn't have a geometry". Is it the same as "geometry is not valid", or does it simply mean ...
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3
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0
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273
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How to measure orthogonal distance of line from point in QGIS?
As I am fairly new to QGIS I'm seeking your help.
I'm trying to measure the distance between points in a point Layer P and the end of lines in a line layer L. In L there are two categories (attributes)...
- 41
3
votes
0
answers
531
views
Interpolating point to nearest polygons to compute street width in postgis
I am trying to calculate the width of streets (line.shp) in postgis using reference point (ref_point.shp) (yellow point features) and building polygons (building.shp). The red point features are the ...
- 1,081
3
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0
answers
627
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Geometry issues when digitising in QGIS
I'm digitising a large number of maps from hand drawn mud maps and digital images, and although I have used the snapping tools ("snap to vertex and segment", Tolerance 10 pixels, avoid intersections) ...
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3
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0
answers
426
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What is the area that OGR extracts from the (geometry) shp files for polygons?
The ESRI July 1998 technical documentation for polygon shapefiles at page 10 makes no mention of either area measures or length measures (apart from byte/record-layout matters). Yet OGR enables me to ...
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3
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answers
108
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PostGIS does not export shortest path to Shapefile
I am trying to draw a bunch of lines overlaying the globe map in a WGS84 projection. To this effect I have created a PostGIS DB with a table that has one column containing linestring data.
My problem ...
- 151
2
votes
0
answers
34
views
QGIS converting MultiPolygon to MultiSurface - can I disable QGIS from doing this?
I have MultiPolygon data stored in a PostgreSQL DB (13.9) and am editing this through QGIS (using 3.28.3-Firenze). Occasionally when editing, some features are saved back as MultiSurface features. ...
- 21
2
votes
0
answers
115
views
Geometry comparisons in SQL
Newbie to GIS here.
Equality can be defined on a geographic value by seeing if they have a collection of the same points. For example, something like:
-- The equality
-- `LINESTRING(1 1, 2 2) = ...
- 131
2
votes
0
answers
60
views
Selecting geographically identical (underlying) line segments and offset them in QGIS
My project has three lines representing three routes along town streets. All three routes lie on the same street for part of their lengths; two of them lie on the same street for another part of their ...
- 1,076
2
votes
0
answers
172
views
QGIS: Calculate distance between two point layers based on matching ID
I have two point vectors in QGIS. One contains several coordinates, which are grouped geographically by a reference in the field name PID.
I also have a point vector of the centroids from each group ...
- 21
2
votes
0
answers
100
views
PostGIS 3.3, ST_DWithin Query - "lwgeom_distance_spheroid returned negative!" by changing third arg? Postgres 11, Ubuntu 20.04
The unexpected error:
lwgeom_distance_spheroid returned negative!
By making a tiny change in the third argument (distance) to ST_DWithin, we get an error in one version but not another. In other words,...
- 21
2
votes
0
answers
17
views
Reconstructing the original geometry of an object by using negativ and positiv buffers
I have serveral objects with a "thin" geometry which are connected by a very slim passage.
My goal is to remove this connection so the object is devided into two separeted features. My idea ...
- 193
2
votes
0
answers
101
views
Exporting curved geometries as a GPKG with linear geometries
I have a layer (based on PostGIS or GPKG) containing complex, curved geometries (think MultiSurface(CurvePolygon(CompoundCurve(CircularString(...).
How can I export this layer as a new GeoPackage that ...
- 10.8k
2
votes
1
answer
243
views
Overlaps function in GeoPandas/GeoSeries is not working
There seems to be wrong with the overlaps function. Suppose I have this GeoDataFrame consisting of LineString geometries only with crs='EPSG:3347:
Then I went ahead to extract only the first row's ...
- 31
2
votes
0
answers
139
views
Automatically update geometry from attribute
Using the field calculator one can update the geometry of a feature in dependence of one of its attributes. The process is described in
Updating feature geometry from attribute fields in QGIS
My goal ...
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2
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0
answers
231
views
Cannot add geometry layer to QGIS although geometry column is recognized
The geometry column POINT in the View (not Table) View_MyGeometry is generated in the SQL database GeoData with Microsoft SQL Server Management Studio. QGIS recognizes this column as a geometry column ...
- 445
2
votes
0
answers
190
views
Languages to represent ellipse geometry (WKB/WKT)
I am new to the idea of representing vector geometries in a text markup language. I am looking into different representations for geometries consisting of smooth curves and three dimensional objects, ...
- 21
2
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0
answers
51
views
Style rule based on feature adjacent edges and ignore vertices
I have a set of square tiles which I want to show in a different colour when the tile to the north, south east & west are present in the same way as below with the links I want in black.
I have ...
- 21
2
votes
0
answers
57
views
How to make a projection of a linear layer on an another layer
I'd like to know how to make a projection of a complex linear layer on an another layer, overlapping their geometries perfectly and considering the extremities of lyr_1; using geoprocessing of QGIS. ...
- 935
2
votes
1
answer
816
views
Snap points to polygon/lines in python shapely?
I have a shapefile of point features
And a shapefile of polygons features
I would like to snap these points to the polygons, as they are often just outside the polygons and cannot be spatially ...
- 449
2
votes
0
answers
386
views
Compute the distance from a point to polygon given the point and direction
I want to compute the distance from a point to a polygon given the point and direction. Currently I am using shapely and defining a "somewhat" infinite line string. This is not ideal as I ...
- 345
2
votes
0
answers
282
views
Seeking Python library to check validity of 3D polygon
In the case of 2d polygons I have been using shapely:
from shapely.geometry import Polygon
Polygon(points).is_valid
But for 3D polygons, shapely simply computes the validity in the x-y plane as ...
- 345
2
votes
0
answers
193
views
Geometry error present only when writing shapefile to disk in QGIS
I have a complex shapefile that I am trying to use for a Difference spatial operation in QGIS (Madiera 3.4). When doing that I received an invalid geometry error.
Using the QGIS Check Validity tool ...
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2
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answers
261
views
Measure length of shadow from object center in QGIS
I am trying to measure the length of object shadows in QGIS 3 in order to calculate the object's height.
In order to know height (h) I will need to have:
The length (l) of the cathetus (line from ...
- 518
2
votes
0
answers
232
views
"Snapped geometry has invalid geometry" error when snapping geometries to layer
I have two shape layers in QGIS where I want to use the "Snap Geometries to Layer". I get the error message that several polygons of the Reference layer have invalid geometries:
Feature (1) ...
- 631
2
votes
0
answers
56
views
Compare two linear layers with geoprocessing tools
I'd like to know how can i have in output two layers, composed by one of the two layers in input, comparing the geometry and attributes of the 2 input layers (test_1 and test_2) using geoprocessing ...
- 935
2
votes
0
answers
58
views
Geometry Object geoprecessing fails
Theoretically, ArcPy geometry objects can be used as inputs and / or outputs in geoprocessing tools, just pass arcpy.Geometry() as an argument for outputs. However, I have come across several tools (...
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2
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0
answers
91
views
Calculating distances between buildings, plots and road network using geometry expression
I am trying to measure the distance between the edge of a building edge to the closest road within the buildings plot to see whether there is enough space for a Electric vehicle parking space.
I have ...
- 21
2
votes
0
answers
64
views
How to automatically clean hollow lines in middle of polygons in QGIS?
I am trying to correct automatically this kind of errors. I already tried the tools v.clean (maybe I have to tune some parameters?) and correct geometries. I also tried dissolving, but since there is ...
- 457
2
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0
answers
148
views
Geometry Type error preventing saving of layer after editing - geometry type is correct under layer information
I have a problem with a linestring layer that doesn't want to be saved after editing.
The layer itself shows 'LineString' under the information tab. When I add a line with the tool by snapping the ...
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2
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0
answers
138
views
Are latitudes -90 and +90 both valid in WGS84?
Geometrically, I understand that a sphere can be addressed in latitude and longitude on the ranges [-90, +90] and (-inf, +inf) respectively.
However, I am working on the specification for plus codes, ...
- 153
2
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0
answers
200
views
Points interpolation on a polygon geometry
I would like to know how to interpolate point data on a polygon geometry.
I have two PostGIS tables:
the first one contains hourly rain values evaluated in the nodes of a regular grid (specified in a ...
- 21
2
votes
1
answer
68
views
Check geometries distorting polygons when removing gaps
Using QGIS 3.10.9 with the check geometries plugin (v0.1), and I have a simple polygon layer as a test run with a deliberate gap.
I use the check geometries plugin with the topology check 'check for ...
- 51