A geometric element defined by a pair of x,y coordinates.
19
votes
6answers
2k 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 ...
14
votes
2answers
2k 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:
...
13
votes
4answers
819 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 ...
12
votes
5answers
10k 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 the corresponding x y coordinates for each point. Is there a way for me to extract a list of coordinates for ...
11
votes
7answers
310 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
8answers
5k 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 ...
10
votes
4answers
620 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 ...
10
votes
3answers
2k views
How to join 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 ...
10
votes
2answers
219 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 ...
9
votes
3answers
2k views
What is quickest way to select polygon by point in ArcGIS 10 using ArcPy?
I keep thinking that I must be missing something, but there does not seem to be a tool in ArcGIS 10 to select features (in particular polygons) from a layer at a point (X,Y) location via ArcPy. The ...
8
votes
2answers
773 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 ...
8
votes
1answer
343 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 ...
8
votes
1answer
126 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, ...
7
votes
8answers
11k views
In arcgis 10 how can I turn a csv file into a point shape file using lat/long data within the csv?
Greetings everyone! 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 ...
7
votes
4answers
8k views
How to find the distance of a point along a 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 ...
7
votes
2answers
668 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 ...
7
votes
3answers
456 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 ...
7
votes
2answers
334 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 ...
7
votes
4answers
2k 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: ...
7
votes
2answers
838 views
For a given feature find the closest point along a given path
Looking for a Java based (foss4g) solution for the following:
I am using a path along with a buffer to find features that are along the path. For each of the features returned I want to find the ...
6
votes
7answers
2k 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.
6
votes
3answers
243 views
Classifying point coordinates to countries or continents?
I have about 50 000 points (latitude and longitude), and I would like to find out in which country each of the points is located. It does not need to be super precise, though.
(Or actually I only ...
6
votes
4answers
3k views
How do I create point features with exact (manually entered) coordinates?
How do I create point features with exact (manually entered) coordinates i Quantum GIS (QGIS)?
I get precise gps coordinates from a survey team which I need to add to a point layer. What I want: -Add ...
6
votes
4answers
235 views
How to calculate the “depth” of a linestring using postgis
I have linestring features, which look like bent linestrings, hemicycles or convex or concave linestrings. In the moment I can select the distance between the startpoint and endpoint of each feature. ...
6
votes
2answers
2k 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 ...
6
votes
4answers
673 views
Output PostGIS geometry data as centroid or polygon depending on zoom level (GeoServer)
This is what I want: when I zoom out, cities of the country should appear as points and at a certain level when I zoom in, I want them to appear as polygons (showing the area of the city and ...
6
votes
4answers
637 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 ...
6
votes
2answers
185 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)
6
votes
2answers
284 views
How to Match Point Data in QGIS?
Please, how do I match the same points (WGS84) in two different point layers? Like I want to get the points that lie exactly upon each other in the two datasets.
6
votes
2answers
119 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 ...
6
votes
1answer
201 views
How to draw shapes with highest possible decimal accuracy
I am trying to read input of lat and long to draw the shape based on condition.The input is standard array of lat and long with 15 decimal accuracy. I am realizing - I am loosing some decimal accuracy ...
6
votes
2answers
189 views
Why am I getting duplicate ghost points (features), i.e., one point in the feature class but two points?
When editing some of the attributes in a point feature class in ArcMap 9.3, duplicate labels started showing up. When I click on the point, I discovered that the point has duplicated itself BUT there ...
6
votes
3answers
721 views
Converting point data into a weighted raster
I am completely re-writing my question as i think it was quite confusing before:
I have a number of different points, each point has a -z value.
I need to create some sort of raster or a series of ...
6
votes
1answer
519 views
Interpolation: irregular shape, merging DEM's
my problem is quite complex, though I hope that solution may be simple or at least possible.
I do have .img DEM 0.5x0.5m. DEM consists of river bed, river valley and adjacent areas (it is strip of ...
6
votes
1answer
255 views
QGIS or Postgis - How to split polylines with a point layer?
In QGIS, I would like to split the polylines in a layer loaded in the workspace with the points in another loaded layer. If a point intersects a polyline, this polyline should be transformed into two ...
6
votes
1answer
110 views
How many GIS projects deal with just basic “putting markers on a map”?
Is there an academic paper or conference contribution, where someone estimated how many GIS projects actually deal with only a very basic usage of GIS data? Something equivalent to the infamous "80% ...
5
votes
3answers
180 views
Methods for lat/lon quality control?
I have a database with fields including latitude, longitude, city, state, and country.
When mapped, it is clear that a number of the sites are in the wrong location - most commonly because of a sign ...
5
votes
3answers
126 views
GIS file format for space and time data?
I need some advice with GIS file format choice.
Here is my problem:
I have about 100 stations.
At each station water temperature is measured daily for 1 year
I want to load this data to QGIS and be ...
5
votes
1answer
194 views
How to determine optimal windmill placement to maximize production?
How can I add automatically the maximum number of points (dots) with 6m diameter and 100m distance each point from other into an area. The dots will present the windmill base (6m) and I want the ...
5
votes
3answers
262 views
Is there a tool to add “noise” to overlapping X, Y coordinates so they are no longer in the EXACT same place?
I have a series of points representing animal observations. Many of them overlap, having the exact same coordinates, and this is causing me trouble when I want to run some analytical tools which ...
5
votes
9answers
7k views
ArcGIS: Create a line layer from a point layer and csv data file
UPDATED DECEMBER 20
I have a Regular point layer and a csv file that has the same ids as the point layer. The csv file is organized as
ID From To Weight
-- ---- -- ------
01 ...
5
votes
3answers
1k 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. ...
5
votes
1answer
2k 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) ...
5
votes
3answers
926 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 ...
5
votes
3answers
242 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 ...
5
votes
1answer
138 views
Given 2 LINESTRINGs with common point, how to extract common point?
I have 2 LINESTRING geometries. I know both share a common point. Using PostGIS for Postgres, what is the cleanest way to extract the common point?
Example with illustration:
How do I extract the ...
5
votes
2answers
102 views
How can I join a spreadsheet to a point layer?
I have a layer with point data for the grave positions in our cemetery. We are gathering data from each headstone. If I enter the data to a spreadsheet can I later associate the spreadsheet with the ...
5
votes
2answers
602 views
Creating a line (closest vertex to line)
I am working in reorganising our utilities data. Only since two years ago, we have started collecting Water Private Service line. We still have a lot of them to extract from old Record Drawing.
...
5
votes
3answers
2k views
Is there a way to label points in a regular interval in ArcGIS 10? [SOLVED]
Estou trabalhando com linhas em estradas representadas por uma grande grande quantidade de pontos em sequencia.
Uma vez que colocar o nome de todos os pontos tornaria a identificação impossível, ...
5
votes
2answers
1k 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 ...
