Tagged Questions

Where features overlap

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0
votes
1answer
81 views

How to find line segment between line intersections?

Given 1 non-self-intersecting line (red) and 2 other non-self-intersecting lines (light-green), what is the best way to find the coordinates of the line in between the 2 intersections? I threw this ...
1
vote
1answer
791 views

OGR Layer Intersection

I am using what I would describe as the most primitive method of doing intersection with OGR. The short script below describes how I do it. Is there a best way of doing this? from osgeo import ...
0
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0answers
109 views

Draw point on google map

i try to add google map on my own wms and wfs layer. everything works but when i create point, i intersect point geometry and my geojson data. So without googlemap it was run. But when add google map, ...
1
vote
1answer
62 views

How to preserve line segment ObjectIDs in point output from line Intersect?

I am using the Intersect tool in ArcGIS for Desktop 10.1 to identify all the intersections in a polyline shapefile. The tool generates a point shapefile, but when I inspect the data it does not ...
0
votes
2answers
159 views

Intersect and MBR in POSTGIS and Mysql

I would like to know if POSTGIS and MySql with Spatial Extension use true geometry to find intersections/overlaps between geospatial objects. But i don't find it precisely in the documentation. I know ...
7
votes
1answer
864 views

Find Nearest Line Segments to Point

Background From a known Point, I require to establish the nearest surrounding "visible perimeter" against a table of MultiLineStrings, as shown on the diagram. I've searched this site with a number ...
1
vote
1answer
172 views

creating a st_contains query with geographies not geometries

I'm trying to find all the geography points that are contained in a geography polygon, let say all the traffic lights within a given city or neighborhoods, how can i convert this working st_intersect ...
1
vote
1answer
113 views

determining what polygons intersect another layer

I am attempting to establish what spatial relationship exists (if any) between two layers. I have two layers - one is a road network with a buffer of 500m, and the other is a collection of polygons ...
1
vote
2answers
299 views

unionize intersections of merged polygons

[Updated quesion] I am using the following code to merged polygons from shapefiles for the purpose of calculating the surface area; library(maptools) library(rgdal) library(rgeos) #enter slots, ...
2
votes
1answer
262 views

Creating buffers that will not overlap in QGIS

I am dealing with a .shp with a number of points in it. The distances between points range from ~300m to 5km. I wish to create a 1 km buffer around each point with as little overlap as possible. Each ...
2
votes
3answers
307 views

Produce a list of polygons that a line crosses

I have a polyline feature class and a polygon feature class. What I want to do is add a field to the lines that lists all polygons that touch the line. This is effectively performing a ...
1
vote
1answer
66 views

Mismatch in area calculation using Field Calculator vs Group Stats in QGIS 2.0

I have two polygon files (A being my area of interest and B being a categorised land cover layer). Both layers were in the same projection (projected and not geographic). Using QGIS 2.0, I used the ...
1
vote
1answer
92 views

Separating distinct lines in PostGIS

I have a table of linestring segments in Postgis. These segments make up distinct non-intersecting lines as shown by the diagram. To add confusion the direction of the linestrings are not uniform. I ...
2
votes
2answers
148 views

How to check if vertex exists (on polyline) based on location of point layer using ArcPy?

Using ArcGIS for Desktop Advanced 10.1 (with all extensions) I am building a centerline network that will be used by a MapObjects program to do routing based on "turns at any vertex" (as opposed to ...
0
votes
1answer
295 views

Maximum size on the bounding box with ST_MakeEnvelope and && and geography column in PostGIS?

I've done quite a few google searches, but haven't managed to find anything that has helped me directly. I've got a few features in a PostGIS table with a geography column. The features are focused ...
3
votes
2answers
157 views

Is there a way to speed up gIntersections for large spatial objects?

I'm attempting to perform a gIntersection of a big grid on a shapefile for country boundaries, so that I can calculate the % area of each grid cell that lies within the country. It takes a few seconds ...
0
votes
0answers
22 views

Program crashes when trying to do intersection.

I'm trying to get the intersection between a highways shapefile and some states in Mexico but it seems that the program always crashes. I attach the images of what I'm trying to do and the error that ...
0
votes
1answer
227 views

Intersecting polygons in Oracle

Have a polygon in table 2 with its id, no and geometry. In table 1 I have polygons with the same fields. The polygon in table in intersects with a few polygons from table 1.What I am trying to do is ...
2
votes
2answers
185 views

Separate a polygon in different polygons depending of the distance to another polygon

I have a reference polygon "R", and others polygons (in grey). I want to separate each grey polygon in multiple polygons, depending on the distance to R with different Buffers : - The red line is R ...
2
votes
1answer
530 views

PostGIS: Calculate the length of just the portion of linestring that intersect with a polygon

I want to calculate the portion of the linestring that lies within the limits of a polygon. Better with an image What is the length of the portion of linestring within Province A? and within ...
4
votes
1answer
536 views

How to use the Intersects function in the Field Calculator of QGIS?

I would like to have an example on how to use the Intersects function in the Field Calculator of QGIS. Basically, I want to know which feature from a polylines layer intersects a polygons layer and ...
2
votes
3answers
1k views

Intersect (analysis) of polygons generating empty output

I have previously asked a question on determining the area of polygons with another polygon boundary. Determining the area of each polygon within a polygon boundary? I came to the conculsion that ...
1
vote
3answers
269 views

ST_Intersection point of two 3D linestrings - how is the Z value calculated?

I have two 3D linestrings (geometry type LINESTRING Z) in a PostGIS database that intersect in 2D space, but not in 3D space. Given that there is technically no 'shared portion' of geometry in 3D, how ...
1
vote
1answer
107 views

Load Raster Values into Shapefile [duplicate]

I have a shapefile containing many points. Some of these points fall within an area for which I have raster data. I would like to load the values of the raster which underlie each point into the ...
3
votes
2answers
200 views

geospatial libraries like postgis

I'm pretty comfortable with postgis, but I realized that for part of my application, having a database is pretty heavy. I'd like to be able to take a stream of Point objects and check against an in ...
6
votes
1answer
404 views

Performance in calculating raster statistics in PostGIS

I'm trying to calculate raster statistics (min, max, mean) for each polygon in a vector layer using PostgreSQL/PostGIS. This GIS.SE answer describes how to do this, by calculating the intersection ...
1
vote
1answer
216 views

How to calculate the intersect two shapefiles [duplicate]

I have two shapefiles. 1. the clinic buffers 500m area. 2. the postcode area. Is there a simple way to calculate the intersect two shapefiles ? I'm using QGIS Dufour. I tried to use fTools to ...
1
vote
1answer
97 views

How to perform intersect operations in the Field Calculator in QGIS?

How to use the Intersect function? How would I specify to REPLACE layer1.field1 with layer2.field2 WHEN layer1.geometry INTERSECTS layer2.geometry Is that feasible in QGIS?
2
votes
0answers
75 views

How to copy the contents of an attribute from one vector layer to another one that touches it or intersects it?

I have 2 layers that intersect, called layer A and layer B. Layer A has an attribute (X) that I want to copy wholesale (for the whole layer) to layer B, so that when object A1 intersects object B1, ...
3
votes
1answer
156 views

intersection between two multipolygons yielding anomalous GeometryCollection object full of LineString's & Polygon's (trying to get intersect area)

Normally when I call the #intersection method on a multipolygon to find the intersection shape on another multipolygon I get a multipolygon returned back to me. Either that or something else I can ...
0
votes
0answers
107 views

Line - Line and Line - Polygon intersection in WGS84

What is the correct way (which formula, what algorithm, etc) to determine the intersection point of two lines specified in Lat/Lon coordinates on a WGS84 model? Note that the lines might be very long ...
1
vote
1answer
285 views

Intersection of multi-polygons in postgis

How can I get the intersection of 3 multi-polygons in postgis? I have three geometry collection and I want a fourth with the result of intersection of the other three. ...
2
votes
2answers
2k views

How to delete overlapping polygon features from one of two layers?

I really need your help! I have two overlapping layers of polygons, and i need to somehow erase the areas the overlaps. -This way i should end up with two layers of non overlapping polygons. Sounds ...
5
votes
1answer
807 views

Split polylines at polygon boundaries in QGIS

I have a set of contour lines and a polygon set containing glaciers. Because I want the glaciers to have blue contours, I need to split the contour lines at the glacier boundaries. I can achieve this ...
1
vote
2answers
90 views

Using st_intersects caused mismatch when a marking (tagging) shape marked a polygon overlapping only on the edge

I have accidentally marked a landshape as being tagged "CU GO-M" because it seems to share an edge with a tagshape for "CU GO-M" but nothing else. I used the st_intersects method to join these shapes ...
0
votes
2answers
258 views

Intersection between points and polygons in QGis

I have the following problem. I have a shapefile of points and a shapefile of polygons. I want to know WHAT points (not how many) fall inside EACH of the polygons of my multipolygon shp. I thought ...
0
votes
0answers
208 views

Creating a BATCH with multiple INPUTS (variables) to run a workbench that intersects LINES AND POLYGONS

I'm trying to create a batch file to run my workbench.fmw in which I have two input files: 8 pipeline shapefiles and 96 communal areas shapefiles. The workbench allows cutting pipeline relative to the ...
1
vote
2answers
174 views

Integrate grid and polygon of municipalities keeping the biggest municipality per cell with QGIS (or another)

I have a 9x9 grid and a polygon of municipalities of an extensive area of Brazil. My goal is to have a field indicating the biggest municipality per grid cell. I've been trying with intercept without ...
1
vote
0answers
51 views

Broadband coverage GIF image layer needs to be selectable (ArcGIS)

I am working on a project on Arcmap where I have 80,000 co-ordinates of postcodes and a broadband coverage map. I need to know which of the co-ordinates intersect with the coverage map. I have added ...
4
votes
1answer
743 views

Obtain voronoi polygons which extend till the boundary of another polygon

I have certain hubs (coloured yellow) in a district (coloured light blue). I need to find polygons indicating the closest hub to every point in the district. The voronoi polygons that I obtained ...
0
votes
1answer
54 views

Is it possible to draw a point interactively and execute an intersection operation (drill down) to identify spatial relationship with other layers?

Is it possible to draw a point interactively and execute an intersection operation (drill down) to identify spatial relationship with other layers using GeoServer? I am a newbie with GeoServer…
2
votes
1answer
48 views

Need to put points on overlapping boundaries

I have two layers: a route (Line) and a county boundary (polygon). I need to intersect them so that the output layer is a point layer. The ArcGIS Intersect tool places a point where the route passes ...
1
vote
3answers
124 views

PostGIS intersect on insert?

I have a large amount of point data that I have in CSV form. I am able to insert it all into a PostGIS table no problem. What I want to do though, is split the data up on insert into multiple separate ...
0
votes
2answers
602 views

Detecting invalid polygons (self-intersecting or touching)

An invalid polygon can be defined as one that intersects itself, or one where the lines make contact, ie, the two shapes at the top of this picture. Given the XYPoints of a polygon, what logic ...
0
votes
0answers
75 views

Vector/Raster Intersection - Speedup and replacement for ST_Centroid

I have some raster data which is the altitude above sea level and also some vector data which represents building outlines. What I want to do is grab some buildings outlines and fetch all the raster ...
1
vote
0answers
100 views

how to avoid Intersection of polygons via python code

i am using QGIS 1.8 and i can set the check box in Setting\Snapping Options "Snapping and Digitizing " dialog to avoid polygon intersections and enable topological editing but i am looking for a way ...
1
vote
1answer
69 views

st_intersects on postgis

I'm trying to write a command to see whether a given point lies within a multipolygon boundary (in this case, a watershed). I have a table of watershed boundaries and another table with the point I'm ...
2
votes
2answers
107 views

How to hand over polygon attribute to new point while digitizing?

My task is to work with bird observation data in an area, that is divided into zones as different polygons (A1, A2, etc.). I have the hand-written lists of observations and want to bring all entries ...
2
votes
1answer
69 views

Intersecting Layers Returns Empty Collection Despite Visible Intersection

When I perform an intersection of a polygon I draw in OpenLayers and a postgis database layer, it seems that I am getting incorrect results. Intersection works correctly on some layers. For ...
4
votes
1answer
505 views

How to split a polygon using R

I have an irregular polygon which is a spatial object. I want to divide it into multiple polygons (say, n=25) with equal height. To show how I want to divide it, I've plotted grids on the ...