The measure of separation between two entities or locations that may or may not be connected, such as two points.

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13
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6answers
4k views

What tools in Python are available for doing great circle distance + line creation?

I need to use Python to create a great circle distance -- both a number, and preferably some kind of 'curve' that I can use to draw in a client-side map. I don't care about the format of the curve -- ...
2
votes
1answer
76 views

How to compute the distance from the beginning of a line for every points using postgis

I have a line, for which I need to know, for every point that compose it, what is the distance from the beginning. The data is stored in PostGis 2.0 For example, for the line with the point a, b, c, ...
1
vote
0answers
151 views

Can QGIS Measure Line tool compute correct geodetic distance?

As I understood, this tool normally shows distance in the project CRS units, not the geodetic meters (despite it actually says the distance is in meters). However, now I read (Section III, 4 - ...
2
votes
0answers
197 views

Specifying a bounding rectangle using Google's S2 package for spherical geometry [duplicate]

This is my first post on GIS, I hope it is not too trivial a question. I work on a project on Google AppEngine, which is backed by a NoSQL datastore. This makes a proximity filter different from ...
2
votes
1answer
78 views

Where would a perfectly vertical vertical tunnel through the earth come out?

I am a programmer. I have a point P1 (lat,lon) given by GPS (WGS84) and I want to know the location of a point P2 if I make a straight line from P1 to the other side of the earth. I have read some ...
4
votes
1answer
340 views

meeting point minimizing travel distance for participants?

The problem is to find the point minimizing the travel distance for around 100 persons in different regions who want to meet in the same place. Travel is by car not by plane. Assuming that I get ...
7
votes
2answers
1k views

projection change to create buffer in QGIS

I am about to become desperate... I like to create buffer around several points - if possible - with a declaration of the size in km of these buffers. Just to show you what I am working with: My ...
3
votes
2answers
192 views

Converting lat lon into co-ordinates (in ft of m)

I have a set of latitude and longitude of a series of points which specific the trajectory of a vehicle. If I consider the first point as the origin (0,0), is it possible to convert the trajectory ...
0
votes
1answer
108 views

How to visualise “distance from amenities”?

I'm interested in calculating for every point the distance to the nearest amenity of each of a certain number of types (train station, supermarket and so on). I think the calculation will be ...
1
vote
1answer
86 views

PostGIS integer loop

PostGIS is very new to me, and I'm having difficulty performing an operation that probably isn't too difficult. I have vector layers each filled with the outline of a landmass through time. I want to ...
3
votes
0answers
165 views

Constructing a Voronoi diagram using a complicated travel time metric

I have in my possession four sets of shapefiles: 1. Locations (points), around 1000 2. Roads (lines), each road has a speed attribute 3. Terrain (polygons), each zone also has a speed attribute 4. ...
1
vote
2answers
283 views

find latlngs that are some x distance away from a point to south to north to east to west

I have a latlng i want to find four points with equal distance from this latlangs in all directions east, west, south an north is there any formula . I am trying to build polygons around higways so ...
5
votes
1answer
963 views

How to generate a point distance matrix using shortest network distance?

My problem is as follows. To start with, I have the following spatial datasets: A road network; 13,000 odd point locations representing populated localities (ie places where people live); Service ...
1
vote
1answer
316 views

QGis creating shape file of several points out of two Excel sheets

I am about to create a Qgis file on which it should be visible which companies are working together. As source I have got two Excel Tables. Table = Distribution Centers Table = Point of sales I ...
4
votes
1answer
121 views

How to calculate average distance from points to points?

I have a point layer of 400,000 voter residencies and a point layer of 500 polling places. I am trying to find the average distance it takes voters to get to their polling location. Distance by road ...
3
votes
0answers
276 views

calculate total Miles in a polygon using Google Map

I have an application that allows the users to create any custom polygon layer on top of google maps, i am interested to know if their is a way to select the road layer in this polygon and then ...
0
votes
0answers
403 views

Bearing Distance to Line tool from dBASE table only draws one line in ArcGIS 10

I am using the Bearing Distance To Line tool to draw geodesic lines to points defined by a bearing and distance. This is an aside, but I will then use the Feature Vertices To Points tool to convert ...
1
vote
0answers
53 views

windows function with points in a mixed (multipoint/point) table

I have a table comprising multipoints (tracks) and points (stops between tracks). there can be several consecutive multipoints. now, i want to merge any points lying very closely to each other ...
3
votes
1answer
292 views

Python - OGR: Distance different than in ArcGIS

I want to determine the shortest distance between a point and a line. I use the following Python script to do so. If I compare the result of the script with the result of ArcMap's Near Analysis, I get ...
1
vote
1answer
1k views

Distance between DB field and Point using PostGIS

I'm using Postgresql 9.0 with PostGIS 2.0 extension. I've got the table and geographic field location: =# SELECT * FROM geography_columns; f_table_catalog | f_table_schema | f_table_name | ...
4
votes
2answers
669 views

ST_Distance is not delivering right results

I want to calculate the distance between lat/lon points. I tried the following queries: Select ST_DISTANCE(ST_GeomFromText('POINT(-73.97923 40.75571)', 4326), ST_GeomFromText('POINT(-73.974509 ...
3
votes
0answers
670 views

Performing a Multicriteria Analysis Using Distance Along a Road Network

There is the possibility that I will be working on a project which will look at thousands of properties in a region and measure their accessibility to different services (schools, parks, hospitals, ...
5
votes
2answers
355 views

How to create a point along a line given a distance from another point

I'm trying to figure out a point(D) on B-C that is a specific distance from A. I really don't have any idea on how to proceed with the ellipsoidal math so I figured I'd ask here. How would I figure ...
5
votes
1answer
2k views

How do I perform a proximity search with Postgis?

OK, so I downloaded the Geonames database (cities1000) and wrote a small Ruby program to import them into my table (geo_cities). I then added geography column called geog. So after all of that, I ...
8
votes
1answer
295 views

How to automatically reduce polygon size?

I am working with two polygon layers (counties & states) which I will 'intersect' to find which counties are within which states. Due to data inaccuracies I have to change all county polygons and ...
5
votes
5answers
12k views

For every point, distance to nearest polygon of type X?

In ArcGIS how might one calculate as an attribute value the distance to the nearest polygon of type X? Say we have a point layer of wildlife observations and we want to know how far each of them is ...
3
votes
1answer
46 views

Does IDistanceOP.EucDistanceFull require a projected coordinate system?

I have designed an implementation of ArcObjects' IDistanceOP.EucDistanceFull. It takes its input as a feature class and converts it to a GeoDataset with which EucDistanceFull can work with. It works ...
5
votes
1answer
437 views

How to access the road graph plugin in python?

I am developing a few scripts in Python for QGIS 1.8 to automate some geo-tasks and one of them would be to calculate the shortest distance from a hospital to each building in a town. I would like to ...
15
votes
3answers
2k views

How do I find the distance between two coordinates in an ellipsoid?

Lets say I have two sets of latitude and longitude. How do I find the distance between the two locations if I assume the earth is a perfect ellipsoid (with an eccentricity of 0.0167)?
4
votes
3answers
477 views

How to efficiently find points within an elliptical area?

Using PostGIS 2.0.0 I need to filter the results of a function, which returns many POINTs, to find the ones that lie within an elliptical area defined by two points and a distance (all parameters ...
3
votes
1answer
158 views

Get the total distance from a point to the end of a linestring

I have a list of GPS coordinates that make up a bus route: busRoute = [(x1, y1), (x2, y2), ... (xn, yn)] I also have a point that may not be exactly on that route (due to GPS error): ...
1
vote
1answer
1k views

postgis distance calculation between points with lat, long coordinates

Team, I am new to postgis, but a postgres user for quite a while. I would like to compare the geospatial capabilities between postgresql and mongodb. I have the lat.lon, zip code of US locations; ...
1
vote
1answer
148 views

What is the preferable value for setting tolerance for selecting a feature

I know it's really a basic question. But I am really confused about this. For selecting a point feature by mouse click, we need to set a tolerance value to create the envelope. And here is the problem ...
22
votes
3answers
11k views

Why is law of cosines more preferable than haversine when calculating distance between two latitude-longitude points?

In fact, when Sinnott published the haversine formula, computational precision was limited. Nowadays, JavaScript (and most modern computers & languages) use IEEE 754 64-bit ...
3
votes
1answer
309 views

What formula does SQL Server 2008 use in STDistance?

I am analyzing the accuracy of the STDistance function for geographical objects in SQL Server 2008, in order to understand its behaviour better I need to find the underlying formula. Does anyone ...
13
votes
2answers
2k views

What is the approximate error of the Pythagorean Theorem vs. Haversine Formula in measuring distances on a sphere at various scales?

Many people when first trying to calculate distances between two longitude / latitude pairs ask if Pythagorean theorem works as an appropriate distance function. Most often people answer "no, the ...
0
votes
1answer
59 views

error in estimate distance?

i do some experiment place two sensor node between them 4 meter as distance. then i get these GPS information: node1: Latitude: 32, 33.255 , Longitude: 36, 0.6632 node2: Latitude: 32, 33.228 , ...
3
votes
1answer
544 views

Pivot a polyline at vertex or distance using ArcObjects C#

I hope you can help me with that one. I'm using ArcObjects with C# trying to rotate only one part of a polyline at a vertex or distance along the polyline. The polyline is zAware and has values at ...
1
vote
1answer
465 views

Accurate and fast nearest neighbour, which distance function should I use and how to it speed up? [duplicate]

I am solving the following problem: I have a map with many points in it and I need to find the nearest point to given location. Each point carries information about it's latitude and longitude. This ...
0
votes
0answers
160 views

Offset a Polygon defined in Lat Lng points by a given distance of miles or km

I am trying apply a positive offset/buffer (enlarge a shape equally from the borders) to a polygon that is made up of a series of latitude/longitude coordinates by a distance that is defined in either ...
4
votes
1answer
237 views

API for time and distance between two addresses?

The Google TOS appears to limit the use of API for time and distance between two addresses to use in conjunction with a displayed map. Does anyone know of any other mapping data source that offers a ...
2
votes
1answer
388 views

Correct coordinate systems, but trustworthy distance between points?

I have limited GIS experience with projections and I have some questions about trying to accurately display point data from two different sources in ArcGIS 10.1 in order to do a proximity analysis. ...
0
votes
0answers
20 views

Distance from rivers-Zonal Statistics [duplicate]

I am using arcgis 10.1 I am trying to calculate euclidean distance from each feature using this large rivers shapefile http://www.arcgis.com/home/item.html?id=44e8358cf83a4b43bc863646cd695945 . And ...
9
votes
1answer
268 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, ...
1
vote
1answer
693 views

Get the distance from a point on a polyline to polyline's from point

I have a polyline and a point on the polyline. I need to find the distance from the from point of the polyline to that point. ICurve.QueryPoint method does the opposite thing. It gives a point ...
2
votes
1answer
573 views

Trilateration 3D - Vincenty's Formula

with reference to Trilateration using 3 latitude and longitude points, and 3 distances. The accepted answer was votes as shown in wikipedia at: http://en.wikipedia.org/wiki/Trilateration in ...
4
votes
1answer
229 views

Distance from waterways

I have an sdc file with water bodies, i.e. oceans-rivers-lakes. I want to combine it with a shapefile with the boundaries of countries all over the world and produce two measures: 1) The average ...
0
votes
2answers
246 views

Road network Analysis

I have a Road layer and Point features of some Bus stops from the same area.I want find the Road distance between the Bus stop.Please help me find it. I have QGIS,ArcGIS,and FME. Thanks, RKM
1
vote
0answers
378 views

Get the distance between 2 WGS84 GEOSGeometries

I currently want to check if 2 given GEOSGeometry objects of type Point are within 100m of each other. (length flexible) Looking at previous asked questions on this topic, most of the answers were ...
3
votes
2answers
850 views

Calculating the distance from each point in one layer to the nearest point in another layer

I am trying to find the average distance from several points in a layer to points in another layer. I am using ArcMap Basic - I know there is a way to do this using the Advanced version of ArcMap but ...