Where features overlap
16
votes
4answers
3k views
Separate polygons based on intersection using PostGIS
I have a PostGIS table of polygons where some intersect with one another. This is what I'm trying to do:
For a given polygon selected by id, give me all of the polygons that intersect. Basically, ...
13
votes
2answers
1k views
Identifying road intersections using PostGIS
I'm trying to identify where roads intersect each other, and to make a point at this intersection, with the number of roads that form the intersection listed.
I was wondering if there was some way ...
11
votes
4answers
1k views
PostGIS: Select features that do NOT intersect
This seems to me like such a simple question (and it probably is) yet I cannot seem to find an example that gives me the answer. Using PostGIS, I just want to select points that fall outside of ...
11
votes
5answers
3k views
How to use ST_Intersection?
Here's a quick summary about what I'm trying to do: I have 3 tables in Postgres, 'a' and 'b', each have a Polygon column, and 'c' has a Point column. What I'm trying to do here is to get the ...
8
votes
4answers
1k views
Best way to find the polygons crossed by a line
I'm trying to find all the polygons crossed by a single line (a GPS track).
I'm using the OGR library (from python) for computing this, but it's currently a bit 'brute-force' (and slow). For every ...
8
votes
4answers
2k views
Lines that intersect vs. Lines that touch - how to distinguish?
How do I distinguish between these cases in ArcGIS 10? I am looking at the Trim Line function but that's not what I want (destructive).
Case 1: Both endpoints of a line touch another line
Case 2: ...
6
votes
2answers
2k views
How to create a new layer from overlap between two layers?
I'm new to desktop GIS, and will try to ask while lacking the proper terms from the GIS lingo:
If QGIS was like Photoshop I would like to make a selection from one layer, and then match that ...
6
votes
1answer
518 views
Intersection of multiple layers in PostGIS
I need to write PL/pgSQL stored procedure for calculation of intersection of multiple layers. For example, for three layers A, B, C this function should return ABC geometry:
Function takes as input ...
5
votes
7answers
2k views
Intersection algorithm that correctly handles the 180° meridian and poles?
Is there a well known intersection algorithm that correctly handles 180 meridian and poles?
For example, let's say we have a list of latitude and longitude values that represent Antarctica. Let's ...
5
votes
2answers
297 views
Best strategy for polygon search?
I have a fairly simple question. What is the best strategy to do the following scenario? I think this is a very common scenario:
I have a several thousands of dataset with polygon/points. Each ...
5
votes
1answer
164 views
Intermediate points on a small circle
I need to interpolate lat/lon points along a small circle, with a given centre and radius. I've successfully used these formulas for great circles. What is the equivalent for small circles?
5
votes
2answers
851 views
Calculate area of intersecting polygons in QGIS
I have two collections of shapefiles:
1 - postal codes, administrative and political areas
2 - various land use categories like parks & allotments, and points like trees
I want to produce ...
5
votes
3answers
302 views
Extract Overlapping Polygon Data to Points
I have a polygon data set of corn yield collected by a combine. However, as the combine drove through the field, there was slight overlap between passes, leading to overlapping polygons within the ...
5
votes
2answers
794 views
Need help calculating forest cover within a buffer when it overlaps with other buffers
I'm new to ArcGIS and having real trouble getting this done… Hopefully someone can help. Thanks in advance!
I have a layer showing forest cover in a landscape. I'm trying to create a 5km buffer ...
5
votes
1answer
250 views
Intersect between Surface and Ray
I am interested in finding the intersection of a Ray and a Surface in ArcObjects.
I already know of two solutions. First solution is to use the Locate method of ISurface:
Dim intersectionPoint As ...
5
votes
1answer
792 views
How do I find the intersections of 2 circles on earths surface?
I have the circles' center in lat & long, as well as the radius in meters. How do I find the circles intersections?
Edit: EXAMPLE:
Circle 1: Center on Earth's surface (43.564627,-116.220524) ...
5
votes
1answer
291 views
ArcGIS Intersect using Geometry Service
I am using the intersect service from the ArcGIS Geometry service.
referring : http://help.arcgis.com/en/webapi/sil....htm#Intersect
I have modified it to make it work with polylines
it works fine to ...
5
votes
1answer
287 views
Apportioning Points at a street intersection (arcgis or mapinfo)
I can't seem to find any evidence of this question, but I'm surprised by that, so pardon if this has been asked.
If one is mapping crime location reports, by XY coordinates to streets, to create ...
4
votes
2answers
109 views
Creating space at intersection of two links
I have a shapefile consisting of two links which are crossing over each other.
I want to create an empty space at the point of intersection of the two links.
As of now, I have been manually doing ...
4
votes
1answer
1k views
How to get the intersecting polygon of two polygons? (using JSTS intersection)
I want to intersect two polygons within an OpenLayers layer. I found the JSTS library, which should be able to intersect two polygons, and return the new created polygon of the intersection.
The ...
4
votes
2answers
225 views
How to select features that intersect but don't touch (using ArcObjects)?
So how do I do that? ArcMap's Select By Location selects also all features that touch, but I only need the ones that actually intersect the area.
I currently use ...
4
votes
2answers
179 views
No intersection found between polygons I know intersect!
I'm using two geographies: one is made up of small areas (about 2200), the other large areas (about 70). Both cover all of Australia, and the small areas are not necessarily nested inside large areas. ...
4
votes
2answers
314 views
How to Intersect between a vector (administrative areas) and a raster layer (slope)?
What I've got:
1: A vector-layer with administrative areas of my country
2: A raster-layer with the slope of the terrain of the same country (it is derived from SRTM elevation data with QGIS)
What ...
4
votes
1answer
377 views
Spatial Join in PostGIS according to Line Attribute
I am in the process of building a data warehouse in PostGIS, that will store the length of the road network of a country (Lines) per Administrative Area (i.e. Province or State, referred to as AA ...
4
votes
1answer
549 views
PostGIS geometry intersection test results different for Point and Linestring
Can anyone please tell me what I'm doing wrong, and how do I avoid the problem? I'll attempt to clarify what I'm doing as things go along.
The geom column is a multipolygon column, all values are ...
4
votes
3answers
117 views
Trying to combine nearby points into a polygon
We have collected millions of cell phone strength readings. I am trying to group points of the same strenght that are within a distance of each other in to a polygon. I asked on the
postgis mailing ...
4
votes
2answers
279 views
is there a way to tell if two linestrings “really” intersect in JTS or GEOS
In JTS (or GEOS) you can't tell if two linestrings really cross each other. The result is exactly the same whether the lines simply have a point in common but don't cross or if they really cross.
Is ...
4
votes
1answer
1k views
can I extract overlap of polygons within the same layer?
I am trying to extract the overlap of polygons that are within the same layer in 10. The layer came from a buffered street centerline and I'm trying to extract and delete the intersections from the ...
4
votes
1answer
195 views
adding multiple points to a linestring in PostGIS
Though a newbie to PostGIS, I'm having trouble solving something that I think should be farily straightforward.
I have two linestring tables, both consisting of simple, 2-node line objects: one has ...
4
votes
2answers
112 views
Keep nonintersecting polygons during clip
I am using ArcMap 10. I have two datasets, one of which consists of many small contiguous polygons, and one which has many small non-contiguous polygons. The first dataset is census blocks, and the ...
4
votes
1answer
274 views
Line intersection with circle on a sphere (globe or earth)
How can I find the intersection point of a line and a circle on a sphere (on earth)
Please, if any one knows a good solution help.
Thanks in response :)
4
votes
1answer
280 views
automating forest cover calculations with Python
I have a layer of forest cover comprising ~ 30,000 individual forest patches, and I need to calculate the amount of forest cover within a 5 km buffer of each patch. The buffers all overlap each other, ...
4
votes
2answers
392 views
OpenLayers - Get features inside a polygon
In my OpenLayers map I allow users to draw an ad-hoc polygon vector. Then I need to get all the features from a WFS vector layer that fall within the ad-hoc polygon.
Here is the code I have that ...
4
votes
1answer
184 views
Finding intersection density for weighted lines connecting points across the continental USA
I'm working on an one-time problem that I'm hoping to solve with a computer program using free GIS libraries (preferably for VB.Net, C#, or Python... Java or C/C++ could work too). Alternatively, I ...
3
votes
3answers
140 views
Is the Intersection Operation Commutative?
In map overlay, is intersection of map layers a commutative operation ie layer_A intersection layer_B = layer_B intersection layer_A?
If layer A is a square and layer B is a triangle. In this case, (A ...
3
votes
4answers
196 views
How can all polylines within a polygon be selected and then operated on to determine the average value from an attribute field?
I have two files illustrated wonderfully below: 1) Polyline (shown in red), 2) Polygon (shown in black).
The polyline file contains a numeric attribute (elevation in meters).
I would like to select ...
3
votes
3answers
131 views
ArcObjects C#: select intersecting polylines
My questions seems trivial but it is a real blocker for me. So please help!!!
How can I, using ArcObjects with C#, select only those polylines in one layer that intersect with each other?
It sounds ...
3
votes
2answers
2k views
Measure the area of a polygon resulting from the intersection of two other polygons?
How can I measure the area of a polygon resulting from the intersection of two other polygons? If I use the measure tool or open the attribute table for the resulting polygon, it shows me the areas of ...
3
votes
1answer
108 views
Postgis: aggregate function for intersection
I have a PostGIS Table with LINESTRINGS.
I like to a query that returns all Roads that are connected.
So I get a set of unconnected trees (in german 'Wald (Graphentheorie)')
pseudo code:
select ...
3
votes
2answers
643 views
Find intersection points of two polyline features
I'm currently working with street intersections trying to find point(or points) where 2 given streets intersect(!disjoin). Streets are all Polyline features, and I have to work with 2 features at ...
3
votes
2answers
507 views
Selecting points not snapped
I have a point layer and a polyline layer. I want to select all points in the point layer that are not snapped to a vertex in the polyline layer. How can I accomplish this? I'm using MapInfo and ...
3
votes
1answer
802 views
Intersect two polylines using ArcObjects
I have two polylines and would like to find the intersection(s) using ArcObjects / VB.NET.
I'm using the following code:
Dim topoOp As ITopologicalOperator = TryCast(pTestPoly2, ...
3
votes
2answers
414 views
How do I find the points of intersection between a small circle and a great circle?
I only actually need to intersect a great circle arc i.e. the shortest path between two points, with a given small circle.
I found this tutorial for intersecting two great circle arcs, but ...
3
votes
1answer
132 views
PostGIS: Using a polygon to 'mask' linestrings returns both multi and linestrings
I have a table of linestrings (OSM roads, in fact) that I'm displaying on a map. I want to filter them so that only those within a certain area are displayed- I've already done this with the coastline ...
3
votes
1answer
269 views
select polyline intersections from one shapefile using QGIS
I'd like to find out if there is a way to select all of the polyline intersections within one shapefile. The lines are a road network. I've looked through the posts, and the only tip I can find is the ...
3
votes
1answer
295 views
Is there a commandline tool for intersecting Shapefiles?
in QGIS vectorlayers can be intersected. That is apparently done by ftools and seems to be integrated into the QGIS-program itself.
That is different from many other functions that call GDAL-tools.
...
3
votes
1answer
224 views
ArcMap: extracting overlapped buffers
I have a set of points in ArcMap which I create a buffer for each point. Then I use intersect to extract the overlapping buffers. The result is something like this:
The lighter color are the ...
3
votes
1answer
332 views
ITopologicalOperator.Intersect, how does this work?
I'm trying to intersect all features of a layer with another's but I'm getting the web ADF application stuck while executing the "ConstructUnion" function
Here's the code I've written so far
// ...
3
votes
1answer
73 views
Help with intersections in QGIS
I have a shapefile which defines for me the area of each oil field in the North Sea (~300 fields). I also have a shapefile which defines the location of every well that has been drilled (~13000) ...
3
votes
1answer
236 views
ArcObjects 9.2 SDK: How to intersect two SelectionSets (in-memory pointers) and return a FeatureClass?
[Update]
Since posting this question, I've come to the conclusion I'm not fighting flaws in the BasicGeoprocessor object, but more likely having issues with poor object lifecycle management on my ...
