# Tagged Questions

A geometric element defined by a pair of x,y coordinates.

9k views

### How to compare two spatial point patterns?

If I have two point pattern distributions within the same geographic region, how would I go about visually and quantitatively comparing those two distributions? Also assume I have many points within ...
45k views

### Get list of coordinates for points in a layer?

I've got a layer in QGIS that is comprised of points. Its attribute table doesn't have (show) the corresponding x and y coordinates for each point. Is there a way for me to extract a list of ...
46k views

### How do I create point features with exact coordinates?

How do I create point features with exact (manually entered) coordinates in QGIS? I get precise GPS coordinates from a survey team which I need to add to a point layer. What I want: -Add point, type ...
13k views

### How can I convert an excel file with x, y columns to a shapefile?

How can I convert an excel file with x, y columns to a point shapefile? There are some somewhat optional requirements in addition to the correct creation of a shapefile: Column types (as per Excel'...
9k views

### Joining attributes from nearest point in QGIS?

I have two layers with points, call them A and B, each with different attributes. For each point in A I want to join all the attributes from the nearest point in B. Ideally this would also include ...
7k views

### How can I find a point inside a polygon in PostGIS?

How can I find a point that is guaranteed to be within a given polygon in PostGIS? I am aware of the ST_Centroid function. However, the centroid is not always within a polygon, see below: ...
23k views

### Finding distance of point along polyline?

We need to find the distance of a series of point along a given polyline. We have a polyline dataset repsenting rivers in a catchment, broken up into river reaches (FID 1 through 35 for example). We ...
2k views

### algorithm to place maximum number of points within constrained area at a 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 ...
2k views

### How much sense does it make to average (lat,lon) samples in order to increase 2D accuracy of a GPS location?

Several GPS applications, like this one, or this one, acquire multiple (lat,lon) samples of a given location, assuming that the GPS unit is not moving, and then take an average of the samples in order ...
11k views

### How to create points in a specified distance along the line in QGIS？

I want to use QGIS creating points along the line, but in specified distance. I found two GRASS tools in SEXTANTE Toolbox： v.to.points v.segment I tried v.to.points, setting the maximum distance ...
5k views

### Aggregating points to grid using R

I have a question with regard to spatial aggregation in R. What I am trying to do is aggregate a point dataset to a grid. I am unsure however how to do this as I have little experience with this sort ...
14k views

### Converting Polygon into single or all Points using QGIS?

I want to convert polygons into points using QGIS. I know how it's done in ArcGIS Desktop.
13k views

### Extract raster values at points

How can I extract values from a raster by points. I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.
2k views

### Moving points onto lines (~neighborhood)

I do have two vector layer, of which one is a point layer based on "events" by remote sensing and the second one is a line layer from local research. In my case these are earthquakes and tectonic ...
456 views

### Public reprojection services

Are there any free public services where I can send one point in a coordsystem and it returns the point reprojected in a specified coordinate system? I will not be doing many requests, for now it is ...
1k views

### How to model a graveyard - one point per deceased or one per grave? [closed]

This is a continuation of my previous question about our project on how to economically get away with the implementaion of a graveyard in a GIS system… On the graveyard we can find Regular ...
840 views

### Point Pattern Analysis Algorithms

I'm looking for point pattern analysis algorithms and literature on point pattern analysis, online resources and book titles welcome. The topics may range from general descriptions of algorithms to ...
2k views

### PostGIS raster value of a lat/lon point

I have a tiff raster in my PostGIS 2.0 database. I want to get the value of the raster at a specified lat/lon point. I have: postgresql-9.1 postgis-2.0-svn with raster support a raster imported ...
3k views

### How to filter wrong GPS points?

I have a database of GPS points. There aren't any tracks, only points. I need to calculate some value for every 100 meters, but sometimes GPS gave a wrong coordinates that lies far from real GPS ...
7k views

### How to randomly subset X% of selected points?

What methods are available in ArcGIS 10.2 to randomly subset a selection of points. For example, in the attached screenshot I am interested in keeping 20% of the selected points and deleting the rest....
19k views

### Creating polygons around extent of similar points using ArcGIS Desktop?

I've millions of points collected for lithology layer. They have used a coding for different types of rocks. I need to create a polygon around the extent of similar points. What is the easiest ...
9k views

### Get all the points of a polyline

I have some polyline feature objects in python. Now I want to get all the points of polylines. For example, if a polyline has start point [0,0] end point [5,5]. Result: [1,1];[2,2];[3,3];[4,4];[5,5]...
12k views

### Draw lines from points in QGIS

(I found here similar questions but they all reffer to ESRI's programs, and I use QGIS) I have a point layer and need to draw a line passing through or in the vicinity of the points (up to 0.5m ...
2k views

### Creating a line (closest vertex to line)

I am working in reorganising our utility data. Two years ago, we have started collecting Private Service water line. We still have a lot of them to extract from old Record Drawings. I was ...
682 views

### How to identify and simplify point clusters with regard to time in PostGIS?

I just started to work with spatial databases and I want to write a SQL(PostGIS) query for automatic generalizing of raw GPS-tracks (with fixed tracking frequency). The first thing I am wokring on is ...
4k views

I am looking for a simple point shapefile which indicates where the cities of the world are. I cannot seem to find one which is free of charge and meets my requirements. Ive got this one: http://...
3k views

### How to remove small “salt & pepper” polygons from a layer?

I have a map made up of multiple polygons, with a few hundred thousand points very small polygons on within it. I need the larger polygons, but not the points small polygons. How do I select and ...
9k views

### Simple PostGIS ST_Distance query for two points from the same geometry table?

Note: This question was published at Stackoverflow at first. I have a geometry table points_table with SRID 4326 and a few points in it. I need to find a distance between a pair of points (features) ...
316 views

### Proximity in space and time

I have some point data which represent daily lat-lon locations of an animal, with an associated timestamp. I would like to identify all points where STATIONARY = TRUE. A point qualifies as being ...
5k views

### PostGIS: Find points that lie within a set of coordinates

I have a PostGIS db, and I want to find the points that lie within some region (a bounding box). I have two sets of coordinates, from which I can get all four rectangle points that form the box (if ...
340 views

### Measuring distances between simultaneous points

I am working with GPS data and so I have UTM's with DATE/Time information. I have 2 groups of species (moose and wolves). I want to join the information from moose to wolves that match in time. So, ...
238 views

### Point sampling along a pole-wrapping coastline with PostGIS

I am working on a task that requires me to get sample points every 1000 km along coastlines, and have run into a problem with Antarctica. From what I can tell, it seems to be an issue with the use of ...
18k views

### ERROR 000212: Cannot create XY event source Failed to execute (MakeXYEventLayer)?

I have a csv file that is 133mb in size and has over 1.3 million lines of data. Each line of data has its own lat/long and I was wondering what would be the best way to display those points based off ...
8k views

### How do I retrieve start and end point coordinates with Python/arcpy?

How do I retrieve start and end point coordinates with Python/arcpy for a polyline feature class? I expect to pass a segment identifier to a subroutine and have it pass back start and end coordinates. ...
5k views

### How to create different diameter circles round points?

I want to map a tree survey. I am thinking that I will plot positional points of the trees and then add other data like tree type etc. to the attribute table later. Is there a way I can have an ...
5k views

### Calculating distance to points in QGIS

Is there a way of calculating the distance to the nearest points in QGIS? In ArcGIS there is a function called Euclidean Distance, which can take an input vector or raster, and generate a raster of ...
776 views

### How can I transform polylines into points every n metres in PostGIS?

Question in pretty much the same as this, but I need to use PostGIS. I have a number of polylines, and want to trasform them into points every n metres along these lines. edit: Thanks a lot to ...
2k views

### How can I create random points along a polyline in QGIS?

I am trying to create random points along a polyline shapefile in QGIS. Basically, like the 'random points' tool in 'research tools' but for polylines instead of polygons. I have tried converting ...
208 views

### Automatic numbering of points during digitization in QGIS?

Does somebody know how to automatically number the points during digitization in Qgis. To explain, when I create the new point there is the window where I must to type the point number. Is there any ...
77 views

### How can I export a list of points as a matrix in ArcGIS 10.0?

I have a grid made of points (see attachment) with values for altitude extracted from a DEM. I need to export these values not as list, but as a matrix of size 50x50 to be read in SciLab. The grid is ...
1k views

### How to add vertices to existing linestrings?

If I have Linestring(1 2, 1 5, 1 9) and a Point(1 3) Is there any function that can merge linestring and point preserving the order so output would be: Linestring(1 2, 1 3, 1 5, 1 9)
250 views

### Algorithms for optimally locating points

I am trying to compare locations of where several thousand facilities have been actually built to where they would be optimally located to minimize travel times of the population (represented by ...
4k views

### Label points at regular intervals using ArcGIS for Desktop?

I'm working with lines on roads represented by a large number of sequencial points. Since labeling all of them would make the points impossible to identify, I'd like to know if there is a way to label ...
3k views

### Creating evenly distributed points within an irregular boundary

I need to create an evenly distributed series of points within a series of oddly shapped polygons (formerly squares, but now squares with donut holes). The way I have solved this problem so far is to ...
219 views

### Is “puntal” an accepted and defined geometric term?

There are definitions for the geometric qualities of polygons and lines: polygonal: Having many angles; hence characteristic of a polygon. Ref: http://en.wiktionary.org/wiki/polygonal ...
1k views

### Creating raster or vector raster from DEM point file?

i have a point shape of 75.000 elevation points in a regular 5 m grid. We now want to create a polygon grid with the elevation points as "centroids". Unfortunately, all attempts to do so fail: I ...
5k views

### How to extract POINT from a [LINE|MULTILINE]STRING

I'd like to create a vectorLayer in QGIS to display all the points that form a LINESTRING or a MULTILINESTRING stored in a PostGIS DB. I think that I need to transform all points of LINESTRING (or ...
2k views

### Easily find centre point of a raster in ArcMap 10 document?

If I have, say, a rectangular and georeferenced raster file loaded in an ArcMap 10 document (.tiff w/ associated tfw), how do I easily find its centre point and store that point in a points vector ...