# 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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### Geometry from multiple selected features into one geometry

Lets see if I can explain what I'm trying to do. First of all I have developed an AddIn for ArcMap that can take one selected feature (Polygon) on a layer, grab the geometry of that feature, and save ...
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### Get shortest distance between two geometries in ArcPy

I'm using ArcPy and using a cursor to step through one polygon feature class. For each of these 'source' polygons, I am creating a SearchCursor to find all polygons in a second feature class that ...
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### geometryType property of Vector Layers in OpenLayers

ORIGINAL: I have a couple questions that are focused around the geometryType property with vector layers. When you create a vector layer you can set the geometryType property to limit the geometry ...
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### What is geometry datatype?

What are the basic that one should know about geometry datatype? How is it computed ? Why do we need geometry data type? Edit: I wanted to know why there is a different datatype called geometry. Is ...
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### Measuring straightness of a curve segment (represented as a polyline)

I'm working on an automatic elevation contour labeling algorithm and one of the factors that I want to take into account when deciding the positions of labels is how "straight" a particular segment of ...
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### Topology - To be, or not to be, that is the question [closed]

Topology, I mean "real" topology, is not a new concept and it's available since a long time in GRASS gis. I won't speculate the reasons myself but, after a long period of spaghetti model ...
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### Problems with Multipatches

I have some polygonal features that have minimum and maximum z values. I'm trying to calculate the difference between a fixed extruded polygons and the sum of extruded related polygons. Here's how ...
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### arcpy Geometry tools give incorrect results?

I'm new to python and arcpy but I've been trying to learn how to run geoprocessing tools using arcpy. I have (for this example) 2 shapefiles, a and b, which are both polygons. From plotting them in ...
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### Any .NET library to calculate polygon area?

Is there a .NET library to calculate area enclosed by polygon made up of geo coordinates (lat longs)?
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### How do I find the points of intersection between a small circle and a great circle?

I only actually need to intersect a great circle arc i.e. the shortest path between two points, with a given small circle. I found this tutorial for intersecting two great circle arcs, but ...
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### Intermediate points on a small circle

I need to interpolate lat/lon points along a small circle, with a given centre and radius. I've successfully used these formulas for great circles. What is the equivalent for small circles?
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### Determine point relation to given line

In ArcGIS engine I have a polyline with From and To points. I also have a Point. How can I determine if the point is located on the right or left of the line on the plane considering the direction of ...
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### ArcGIS 10.0/arcpy: Can't retrieve the points in a polyline geometry obect: any idea why?

My arcpy script builds a Python dictionary, dictCLPnts, that holds the geometry objects of a polyline feature class. The following code snippet shows the attempt to access the geometry object with ...
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### OpenLayers: WFS request to GeoServer to retrieve “name” & “featureNS”

Using WFSGetCapabilities I sent a GetCapabilities request to GeoServer. From the result of WFSGetCapabilities().read(), I can loop each featureType and retrieve some basic info(e.g., name, title, ...
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### OpenLayers + Geoserver: how to dynamically retrieve the “geometryName” of a feature layer in GeoServer

I am trying to get the list of feature layers on GeoServer and then user can add layers into map at anytime they want. my question is: when using OpenLayers.Protocol.WFS loading a layer, is ...
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### Is there a way to convert 3D polylines to 3D points in ArcGIS?

I need to convert a huge number of very dense (densified to 1m) 3D polylines to 3D points. I need each vertex along the line and no duplicates (two of the same XYZ coordinates) if possible. Is there ...
2k views

### Python, shapely library: is it possible to do an affine operation on shape polygon?

I am trying to create a rotated rectangle in lat/lon coordinates. Basically, I have the coordinates of the center and rotation angle around the center. Is it possible to do using, shapely or gdal, ...
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### Visualising WKT geometry string in QGIS

A very simple question: Is there a simple tool in QGIS to graphically visualise geometry formatted as text? Example geometry: "POLYGON((571178 6337246,571178 6402217,598061 6402217,598061 ...
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### Moving graphics in Esri Flex Feature Layer

I have an ESRI Flex 2.3 FeatureLayer with some graphics in it. I am able to access the graphics geometry and parse the geometry as Esris MapPoint class for Flex Api. I am calling the update(x,y,srs) ...
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### Open dataset(s) with centroids or other geometry for WOEIDs?

The Yahoo! GeoPlanet data is available for download but this data only includes the object hierarchies without any associated geometry. Do anyone know if there is an open source for geometry ...
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### How to create Esri Flex Geometry from WKT

I am working with Esri flex 2.3 API, I am also using Abode BlazeDS for server side binding. I am sending a geometry as WKT from server into my flex client and I am looking for a way to convert the ...
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### LinearRing getVertices implementation

I'm fairly new to OpenLayers so please excuse me if this is an ignorant question. I'm curious why the LinearRing getVertices implementation getVertices: function(nodes) { return (nodes === true) ...
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### polygon map overlay algorithm

There are many algorithms for binary map overlay operation in vector data format which take two layers of map and produce resultant layer i.e overlaid layer as output. I am wondering whether there are ...
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### Building orientation and simplification using Opencarto Java library

I need to find out orientation of buildings and perform simplification of sides of buildings with a tolerance. I came to know from StackExchange that OpenCarto has useful libraries for geometrical ...
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### Is the Intersection Operation Commutative?

In map overlay, is intersection of map layers a commutative operation ie layer_A intersection layer_B = layer_B intersection layer_A? If layer A is a square and layer B is a triangle. In this case, (A ...
115 views

### Outward buffering

I get the ConvexHull of a set of polygons using ST_UNION and ST_CONVEXHULL functions using PostGIS. I want to know how to create an outward buffer of the created convexhull in PostGIS?
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### Calculate midpoint from a series of latitude and longitude coordinates

I've got a series of longitude and latitude coordinates which represent a building outline e.g. -0.5485381346101759,53.2285150736142 -0.5482220594232723,53.22842450827133 ...
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### Find closest lat long to an input lat long (SQL Server 2008)

I have a point cloud in my database (SQL Server 2008 spatial). That is about 6 million records. There are 3 columns: id, value, geom. What is the optimal way of getting the 'value' at input lat long?? ...
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### Invalid geometry zoo

Many a time and oft I've spent hours struggling with bizarre bugs resulting from invalid geometries. The symptoms vary greatly, including: Database slowdowns Incorrect\Null query results Log files ...
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### Sort by geometry using INHERITS?

hope everyone's doing well. I have a statewide point data set (parent table: 600K rows, 500 columns) I need to analyze at multiple scales based on several different spatial divisions. I'll also need ...
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### How could I compare polygons with appropriate circle?

My problem is that I have a polygon shape file with 1034 records which are the Greek municipalities. My goal is to compare the shape of every record with the circle. In other words, I want to observe ...
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### How do I find the intersections of 2 circles on earths surface?

I have the circles' center in lat & long, as well as the radius in meters. How do I find the circles intersections? Edit: EXAMPLE: Circle 1: Center on Earth's surface (43.564627,-116.220524) ...
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### Terminology: Polygon or Area?

When writing about GIS geometry I'm unsure whether to use the term "polygon" or "area". In particular, does the word "polygon" suggest a specific type of geometry? For example, a colleague suggested ...
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### Is there a standardized or “most used” dummy Z value?

Creating and importing both 2D and 3D data, I have many times encountered the situation where I have no Z value for a coordinate set, that the value of a Z coordinate seems out of range (like -99, ...
584 views

### Setting Spatial Reference for Geometry Bag using ArcObjects and VBA?

Within the ESRI SDK resources there is an example of combining polygons by use of a geometry bag. The following code appears: 'Define the spatial reference of the bag before adding geometries to ...
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### How to store lines and polygons in JSON documents?

Looking at the increasing NoSQL movement and considering that databases like MongoDB offers a new perspective in flexible data storage for GIS. What is the best way to store lines and polygons in ...
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### Which projection casts rays from a point on the surface of the globe to a cylinder?

What is the name of a map projection that casts rays from a point on the surface of the globe to a cylinder? Some people who make sundials put a map of Earth on the sundial. I want to use the "right" ...
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### Does the Chamberlin trimetric projection map (some) great circles to straight lines?

I know that, in general, the Chamberlin trimetric projection maps most great circles on the sphere to some sort of non-straight curve on the flat map. But what about the 3 special great circles ...
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### Creating line of varying distance from origin point using Python in ArcGIS Desktop?

I'm trying to create a line feature from a single point, using a set distance and angle. Using ArcGIS and Python (I hope). I have a point at these coordinates: X = 400460.99, Y = 135836.76 From ...
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### Update geometry(polygon) of shape file based on a point layer

I have two shapefiles. Polygon shapefile Point file contains some points. Now i want to delete all the vertex of polygon shape file which are available in point file. I am using ArcGIS ...
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### Given a list of surveyor points, what is the algorithm used to simplify the points and retain the terrain characteristics?

Given a terrain and surveyor points sampled from from it or from its contours, is there any algorithm that one can use to simplify the points ( i.e., reduce the surveyor points number) and at the same ...
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### Cutting up a shape file into smaller parts

I've downloaded the 350MB coastline shape file from Openstreetmap, but I really would like to work with a small part of them, is there a way to generate a shapefile of a small area. I'm using MacOSX ...
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### Is the Fourth Dimension used in GIS?

Whilst working with OGR, I came across the following field used define a geographic dataset: COORD_DIMENSION The spatial dimension (2, 3 or 4 dimensional) of the column. Whilst I've used 2D and 3D ...
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### create temporary point geometry feature from coordinates in OGR with Python

I have two shapefiles containing two types of geometry features: one contains polygons and the other linestrings. Because I'd like to use the Within method to check whether the end(or start) of a ...
3k views

### How to create a circle in arcpy

Suppose I have a dataset where each record has an x,y and r (the centroid and radius of a circle). How can I create a polygon feature class containing parametric circles? Sorry to those who have a ...
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### Way to Ensure that the Image Centroid is Within Image Bounds

My application uses the ArcGIS Silverlight API to select polygons from a map layer. It uses the Geometry.Extent.GetCenter() method to get the centroid of the shape and add a thumbtack image at those ...
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### Point (of a linestring) within Polygon using ogr and Python

I'm currently working on a project in which I need to build a topological network out of the geometry features I find in shapefiles. So far using Ben Reilly's open source project I've managed to ...
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### How do i find out geometries for areas?

I was wondering if anyone could help me out with a website which I can use to get geometries for a area. What I'm looking for is something like google maps where I can drag a cursor over a area of the ...