Questions tagged [point]

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

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60
votes
12answers
128k views

Creating point features with exact coordinates in QGIS?

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 ...
48
votes
7answers
96k views

Getting list of coordinates for points in layer using QGIS?

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 ...
41
votes
7answers
17k views

Comparing 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 ...
30
votes
2answers
57k views

Draw lines from points in 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 ditance between the point and the line). The nodes of the line will recieve the attributes of ...
29
votes
5answers
18k 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 ...
26
votes
9answers
17k 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's ...
23
votes
5answers
37k views

Finding distance of point along polyline using ArcGIS Desktop?

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 ...
23
votes
2answers
7k 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 ...
22
votes
2answers
10k 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: ...
21
votes
11answers
55k views

Extracting raster values at points using Open Source GIS?

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.
20
votes
6answers
35k views

Creating points in specified distance along line using 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 ...
17
votes
4answers
22k 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.
17
votes
4answers
4k views

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 ...
15
votes
6answers
16k 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....
15
votes
1answer
10k 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 ...
15
votes
1answer
3k views

Detecting if point is on left or right side of line in PostGIS?

I have a linestring table and a point table in postgis. I know the closest line to any given point. What I need to know is on which "side" of that line is the point. I guess I have to do that by ...
14
votes
1answer
8k views

Converting Twitter tweets into points?

I've been doing some research on using R to datamine twitter, but I haven't really found an answer or a decent tutorial for my question. I'm interested in pulling tweets from twitter with a certain ...
14
votes
2answers
5k 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 ...
14
votes
1answer
3k 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 ...
14
votes
2answers
11k 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 ...
13
votes
3answers
4k 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 ...
12
votes
4answers
2k 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 ...
11
votes
7answers
506 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 ...
11
votes
5answers
25k 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 ...
11
votes
3answers
26k views

City shapefile for free

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://...
11
votes
1answer
18k 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) ...
11
votes
2answers
7k views

Removing small “salt & pepper” polygons from layer in QGIS?

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 ...
11
votes
3answers
1k views

Generating attributes in an automatic way with QGIS?

I want to autogenerate IDs while I create new features. So every time I create a new point, its ID will increase by 1 like the following: Feature 1: id 1 Feature 2: id 2 Feature 3: id 3 How can I ...
11
votes
2answers
2k views

Creating random points along 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 ...
11
votes
4answers
918 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 ...
11
votes
2answers
8k views

QGIS calculate distance of point along a line

I have a polyline (movement path) and points recorded along the line. I would like to calculate for each point the distance along the line in Quantum GIS. I hope for a result which will add a new ...
11
votes
2answers
2k views

Creating line (closest vertex to line) using ArcGIS Desktop?

I'm using ArcInfo 10 SP3. 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 ...
11
votes
2answers
1k 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 ...
11
votes
4answers
6k 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 ...
11
votes
1answer
2k views

Is there a “Disperse Markers” tool for QGIS?

I am using ArcGIS, but either I would like to use QGIS and maybe want to switch completely later. A have a point overlapping problem, as a result of geocoding of addresses. I have not found any ...
11
votes
1answer
431 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 ...
10
votes
2answers
15k views

How to remove duplicate point features?

I have created many .gpx datas with my Garmin device, but due to the amount of data, I have imported the mapping data from my device several times (also because I didn't want it to be lost)... As a ...
10
votes
4answers
15k 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]...
10
votes
6answers
19k 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 ...
10
votes
1answer
30k views

Making POINT from longitude/latitude coordinates in existing table using PostGIS?

I would like to make a POINT using the longitude and latitude columns of an existing table. Here's a link to the documentation of ST_MakePoint. Here's my table: CREATE TABLE sysinst.bio ( oid ...
10
votes
2answers
4k views

Finding centre point of a raster in ArcGIS?

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 ...
10
votes
2answers
4k views

What is a multipoint shapefile?

What is the difference between a multipoint shapefile and a point shapefile. in the creation of a shapefile In ArcGIS it has the choice of point shapefile and multipoint shapefile. But I do not know ...
10
votes
1answer
404 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 ...
10
votes
1answer
6k views

How does FlowMapper Plugin work?

I downloaded the FlowMapper plugin for Qgis and I can't seem to find any information on how it is supposed to work... Also the text seems to cut-off and not fully showing for the input fields so I'm ...
10
votes
2answers
3k 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)
10
votes
1answer
2k views

Select features from different vector layers at once?

I have two vector files in the layers panel in QGIS (V2.8.2, Wien). I am trying to select points from both vector files simultaneously to view in both attribute tables - both tables are set to show ...
9
votes
2answers
6k views

Is it possible to create a point within a Polygon (not a centroid)?

Is it possible (without writing Python code - sorry I'm not a developer) to create a point layer from a polygon layer but ensure the point is within the polygon? The ftools centroid tool is cool but ...
9
votes
3answers
15k views

Retrieving start and end point coordinates with ArcPy? [closed]

How do I retrieve start and end point coordinates with 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. The ...
9
votes
4answers
9k 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 ...
9
votes
2answers
400 views

Create line segments at point coordinates in QGIS

I have a point vector layer with angle field. How can I create line segments at these points with certain length and angle? I did this with style options but I need this physically as lines vector ...