Tagged Questions

(1) abstract geometry; (2) storing geographic data in projected coordinates; (3) a generic ESRI term for vector features; a class for "geometry" objects.

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1
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2answers
149 views

Is there an average size for British postcodes?

Is there an average size for British postcodes? Or a method of determining the size for a particular British postcode? Thanks. Considering creating a related program and this would be valuable ...
0
votes
0answers
42 views

Speed drastically reduced when including geometry, is there a way to improve?

-- EDIT: Issue is that the shape files being used are at too small of a precision and way too large, output was 488M total, looking for different source -- I'm having some speed issues with a complex ...
2
votes
1answer
180 views

QGIS 2.2 rendering problems

i have a problem with some geometry. When i run the check geometry validity i get an error coming back that the rings are not closed, so recangular forms that i have surveyed are showing up as ...
4
votes
4answers
437 views

How to determine if an object is a circle

I have a polygon shapefile that consists of many different shaped features. I would like to identify only those shapes that are circles. Is there a way to do this? Is it a calculation I could do in ...
0
votes
1answer
45 views

Getting wrong value for area of geometry using Spatialite?

I am trying to implement a measuring tool on apple maps for IPAD. As a part of that i collect all the touch points on the map into an array and constructing a geometry object from that and then ...
1
vote
1answer
73 views

How do I convert OS coordinates (X and Y) to longitude and latitude coordinates?

How do I convert OS coordinates (X and Y) - Eastings and Northings to longitude and latitude coordinates? For example X and Y below X (Eastings): 347904 Y (Northings): 287484
1
vote
1answer
106 views

How do I figure out the grid references (Eastings and Northings) necessary to create a circular 1 mile radius around one location?

How do I figure out the grid references necessary to create a circular 1 mile radius around one location? For instance: Grid Reference: SO 47904 87484 X (Eastings): 347904 Y (Northings): 287484 ...
3
votes
1answer
147 views

How do I figure out the longitude and latitude coordinates necessary to create a circular 1 mile radius around one location?

How do I figure out the longitude and latitude coordinates necessary to create a circular 1 mile radius around one location? I don't mind how many coordinates that takes. For instance: Latitude = ...
0
votes
1answer
104 views

Get the vertices on a LineString either side of a point (Sql Server 2008)

I have a point that sits on top of a LineString, both Sql Geometry types. POINT('0.5 0.5') LINESTRING('0 0 NULL 1, 1 1 NULL 1') I want to find the vertices of the LineString that lie either side ...
1
vote
0answers
99 views

Using M 'Measure' value in SQL Server 2008

MS Sql Server 2008 geometry type supports adding Z and M values to geometry objects, including linestrings. However, I cannot find any way to make use of these values, since methods such as ...
2
votes
1answer
721 views

How to draw polygons from the python console?

I've been visiting and revisiting the page on geometry handling in the PyQGIS Cookbook: https://www.qgis.org/en/docs/pyqgis_developer_cookbook/geometry.html but can't seem to figure out how to get the ...
3
votes
1answer
173 views

Get geometry column back when counting points in polygon using PostGIS

I have two PostGIS tables: earthquakes and borders, which contain point data on earthquake locations, and polygons of countries in the world respectively. I want to try and count the earthquakes ...
1
vote
1answer
67 views

Adding geometry to rows with missing X,Y inArcGIS

I have a table with X, Y data that contains many rows with still missing coordinates. Now I would like to edit it in ArcGIS 10 and simply add the geometry for selected lines after identifying the ...
2
votes
1answer
346 views

Multipoint vs point PostGIS

Is it normal to use the geometry type 'multipoint' instead of 'point' knowing that I use it to store only one point. How can I convert from multipoint to point
5
votes
3answers
104 views

What is the PostGIS 2.x equivalent of the pre-PostGIS 1.5 ~= operator?

Stemming from my other question: When would a PostGIS geometry compare using ~= return true when ST_Equals returns false?, what is the PostGIS 2.x equivalent of the pre-PostGIS 1.5 ~= operator? It ...
2
votes
1answer
86 views

When would a PostGIS geometry compare using ~= return true when ST_Equals returns false?

I have a couple of featureclasses in a 10.2 geodatabase/PostgreSQL 9.2.2 database and I've been struggling with the FeatureCompare tool--it is telling me geometries are different on some features ...
1
vote
2answers
89 views

Problem - ST_AsGeoJSON return text with accolade

I am saving a result of ST_AsGeoJSON(..) into csv file. But the results I got can't be interrupted as an object later on. How can I polish and delete the accolades that I don't need. ...
0
votes
0answers
21 views

Is there a way of converting polygon vertices to points using GDAL python? [duplicate]

I have an ArcGIS standard license and I want to convert polygon vertexes to points in a script. Since I don't have a good enough ArcGIS license I've been using ET Geowizards to get the points. The ...
1
vote
2answers
235 views

Get the vertices on a LineString either side of a Point

I have a shapely LineString and defined a shapely Point which lies along the LineString. How can I find the vertices of the LineString which lie either side of the point? (split the line in two). ...
0
votes
0answers
91 views

Which geo-location available in Twitter data should I use?

I am extracting twitter location on my side.Few tweets has perfect location but in most cases additional details are available (i.e. Country,bounding_box,poly lines etc) So confused regarding ...
5
votes
2answers
113 views

Can someone give the absolute lowdown on the following list of spatial operators

Ok, I have to admit, I don't really delve too deep into the semantics of the spatial operators list below, I'm more of a user, I write software to drive the SQL most of the time and don't really think ...
3
votes
1answer
628 views

Multiple geometry columns for points, lines, and polygons in spatialite?

I'm rather new to the GIS world and even newer to Spatialite and trying to create a new DB for our application. I would like to create spatial index(es) on the geometry column(s), but our geometry ...
1
vote
0answers
90 views

Error When Generating INSERT Statements for Geometry Field SQL Server

I am populating a column of linestrings from a list of points in sql with which I use to create insert statements to populate an ID and a geometry field in a table. This creates a temporary dataset ...
1
vote
0answers
114 views

Inaccurate result while clipping on gis data

I am trying clip polyline data using a polygon geometry. I am using itopologicaloperator to do this task. However, resultant clipped data is off by 1 feet. Meaning that the polylines at the boundaries ...
0
votes
0answers
199 views

Feature.geometry.transform not working

// World Geodetic System 1984 projection var WGS84 = new OpenLayers.Projection("EPSG:4326"); // WGS84 Google Mercator projection var WGS84_google_mercator = new ...
8
votes
1answer
294 views

What is the precision of SELECT DISTINCT on PostGIS geometry column?

I wonder what the precision of the SELECT DISTINCT operator is on a PostGIS geometry. On my system, the following query gives me a count of 5, which means that the inserted points are considered equal ...
0
votes
0answers
355 views

Polygon to point conversion in ArcMap

I tried to convert polygons to point using Feature to Point under data management toolbox in arcGIS 10.2 (got it from uni. licensed). I got the point layer but it is not showing anything. I added X ...
3
votes
1answer
264 views

Retrieve geographic coordinates from OSM imported data

We have just finished importing OSM data into our PostGIS (Postgresql) database. And we are having difficulty understanding the geometry of various shapes imported. We run a query to retrieve the ...
2
votes
2answers
167 views

How to convert Point coordinates into CSV format?

The GDAL documentation describes how to convert a ShapeFile into CSV data. The layer create options (-lco parameter) allows to prepend the coordinates of Point features to the actual attributes ...
1
vote
1answer
65 views

Mismatch in area calculation using Field Calculator vs Group Stats in QGIS 2.0

I have two polygon files (A being my area of interest and B being a categorised land cover layer). Both layers were in the same projection (projected and not geographic). Using QGIS 2.0, I used the ...
1
vote
0answers
141 views

pgRouting results to LINESTRING geometry type

I am doing some routing queries, using pgRouting's second version of pgr_trsp function. What I can't do effectively yet is storing the results. That is, I want to able to store in a table: either ...
0
votes
0answers
33 views

Identify primary routes in Postgis

I have a table of linestrings that make up a route network. I want to identify the primary routes and separate out the interconnections. Problem is that the primary routes are split into separate ...
1
vote
1answer
188 views

Get Polygon or IGeometry from Envelope in ArcObjects

I would like to create a Polygon Feature from the geometry of an IEnvelope in C# ArcObjects SDK 10. Is there an easy way how to do it?
3
votes
2answers
241 views

How to rename points by clockwise direction or change starting point in polygon features?

I have a polygon feature class. I convert it to a point. Name of field (for example !Number!) in a point feature converted from polygon "A2"(The first point should be in the upper left corner ...
0
votes
1answer
92 views

How to automate creating box (rectangular) polygons in ArcGIS for Desktop?

Can anyone suggest a way to automate creating rectangle shaped polygons in ArcMap? If I had many 30m x 60m rectangles to digitize and I just want to click a starting corner coordinate on screen, ...
1
vote
1answer
97 views

Clip geometries in table based upon value

I have defined a view in postgres that returns a set of polygons and can be queried as follows:- SELECT wkb_geometry, grade_count FROM ng_schema.grade_count_report [sql.where] order by grade_count ...
0
votes
1answer
77 views

Missing a Geom field in PostGis

I am working in a Database preaparation for that I exported a shapefile from Qgis to PostGis.The Problem is this: In Qgis I can see a Polygon feature but when the same polygon feature is exported to ...
1
vote
3answers
319 views

KML to Shapefile using GDAL (LIBKML) - MultiGeometry data not transforming

I am trying to convert a KML file to Shapefile using GDAL (ogr2ogr). Regular KML files convert fine but KML files containing MultiGeometry features (eg: Geometry containing both Point and Polygon) do ...
0
votes
2answers
157 views

Calculating minimum/maximum width for overlay of two polygon strips in ArcGIS or some Opensource GIS

Is there some solution for calculating minimum and maximum width for overlay of two polygon strips? When I clip these strips the result is another strip with variable width about 1 km and 20 km long. ...
5
votes
1answer
345 views

How is ST_PointOnSurface calculated?

The PostGIS documentation states that ST_PointOnSurface returns "a POINT guaranteed to lie on the surface". It seems like this function could be trivially implemented to give results that satisfy the ...
1
vote
1answer
73 views

PostGIS Geometry folder is missing

I have installed PostgreSQL 9.2 and PostGIS 2.0.3 from Stackbuilder. My template_postgis_20 does not have a geometry table only spatial_ref_sys table. Is that a problem? and if not how can i create ...
0
votes
1answer
102 views

Problem of linear records with zero shape length and no geometry in attribute table

I am working with a bicycle and pedestrian facility file geodatabase in ArcMap. I noticed a some of the records in the shapefiles/feature classes have a shape length of zero in the shape length ...
2
votes
3answers
251 views

Fastest way to join points table to polygons tables in ORACLE

I have two tables in 11g oracle db, one with points geometry, one with polygons. Currently I need to enrich the points table daily with the name of the polygon (country) that the point is inside, but ...
0
votes
0answers
203 views

How to get the top left and lower right coordinates of polygon in ArcObjects?

First of all, draw the rectangle ESRI.ArcGIS.Display.IScreenDisplay screenDisplay = Map1.ActiveView.ScreenDisplay; screenDisplay.StartDrawing(screenDisplay.hDC, (System.Int16) ...
3
votes
5answers
754 views

How to Identify and Delete duplicate vertices?

I am trying to figure out how to delete duplicate vertices. I have successfully determined that there are duplicate vertices using PLTS Data Reviewer, but I am confounded as to how I identify and ...
4
votes
1answer
500 views

Buffer polygon inward by percentage of area [duplicate]

I would like to buffer a polygon inward by a percentage of its area, using the polygons below as an example. How could I shrink each polygon inward resulting in a 35% reduction of area? I am using ...
5
votes
3answers
982 views

How to convert geoJSON to python objects?

New to the site, and to geoJSON, and to python. My goal is to read in a file with geoJSON data, and use it to generate shapes to be used in an application that is using python scripting. Python has ...
4
votes
2answers
763 views

How to efficiently determine if a collection of coordinates (polygon) is an ellipse?

I'm attempting to determine a geometry type based on a collection of coordinates and have come across a situation where I'd like to differentiate between what is a "polygon" and what is an "ellipse". ...
6
votes
3answers
1k views

How to fill a hole in a multi-polygon layer on QGIS 2?

I need to fill a hole in a multi-polygon layer on QGIS 2.0. I've set the snapping option for the layer as follows : mode: to vertex and segment tolerance 4 pixels avoid intersection "enabled" ...
7
votes
1answer
226 views

Draw middle ordinate perpendicular to chord, out to curve, with arcpy

I've been assigned to find the radius of road curves. My boss found this article describing a pretty straightforward method of doing so: find the start/end points of the curve; create a chord; ...