(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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3
votes
2answers
729 views

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 ...
5
votes
1answer
261 views

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?
3
votes
2answers
449 views

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 ...
1
vote
0answers
683 views

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 ...
4
votes
0answers
725 views

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, ...
3
votes
2answers
1k views

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 ...
4
votes
4answers
1k views

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 ...
5
votes
5answers
1k 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, or ...
28
votes
3answers
7k views

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 ...
0
votes
1answer
2k views

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) ...
3
votes
1answer
376 views

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 ...
2
votes
3answers
1k views

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 ...
2
votes
1answer
237 views

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) ...
2
votes
1answer
439 views

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 ...
1
vote
1answer
293 views

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 ...
4
votes
3answers
208 views

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 ...
2
votes
1answer
112 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?
4
votes
5answers
7k views

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 ...
6
votes
2answers
5k views

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?? ...
9
votes
3answers
374 views

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 ...
4
votes
1answer
340 views

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 ...
6
votes
3answers
528 views

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 ...
5
votes
1answer
1k views

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) ...
13
votes
5answers
527 views

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 ...
9
votes
4answers
276 views

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, ...
19
votes
3answers
6k views

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 ...
5
votes
1answer
296 views

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" ...
5
votes
2answers
306 views

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 ...
10
votes
2answers
5k views

Using python in ArcGIS, create a line of varying distance from an origin point

What I'm trying to do is create a line feature from a single point, using a set distance and angle. Using ArcGIS and Python (I hope). Here's the scenario: Say I have a point at these coordinates: ...
35
votes
4answers
7k views

What are the pros and cons of PostGIS geography and geometry types?

My company uses geometry (the_geom) data type for storing geospatial data. I've recently been acquainted to the concept of geography (the_geog) data type which, as I understand it, stores the SRID ...
3
votes
4answers
716 views

Update geometry(polygon) of shape file based on a point layer

I have two shape files. Polygon shape file 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 ...
11
votes
4answers
404 views

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 ...
9
votes
2answers
4k views

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 ...
4
votes
3answers
1k views

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 ...
4
votes
2answers
1k views

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 ...
7
votes
3answers
2k 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 ...
3
votes
2answers
660 views

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 ...
10
votes
2answers
3k views

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 ...
2
votes
3answers
722 views

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 ...
3
votes
1answer
496 views

postgres command to save the line coordinates in openlayers

I am working on project that we create one map ant editing toolbar. Then by using that editing tool bar we can draw point, line, polygon on the map. Next we are converting the line, point, polygon ...
1
vote
0answers
273 views

Export topology tables to txt files using ArcObjects, generating directed graph, and finding intersections

I want to export topology tables to text files: for points: 1 id x y for lines: line id fompoint.x from point.y topoint.x topoint.y for polygons: id line id 1, line id 2... 2 arc ...
9
votes
1answer
436 views

Performing Overlay of Two Triangulated Irregular Networks (TIN)

I am referring to the paper here, section 2.6.1, on the adding and subtracting of two TINs: The addition of two TINs can be determined exactly and stored into a new TIN, because the addition ...
15
votes
6answers
6k views

Converting between Esri Geometry and WKT using ArcObjects?

It seems like there is no means of converting an ArcObjects geometry to the Well-Known Text representation (and vice versa) in ArcGIS ArcObjects API. The only thing I was able to find is conversion to ...
8
votes
6answers
1k views

Real-world example of Affine Transform?

From the Wikipedia article: In geometry, an affine transformation or affine map or an affinity (from the Latin, affinis, "connected with") between two vector spaces (strictly speaking, two affine ...
0
votes
2answers
156 views

modeling of spatial objects

I have a line and polygon in this image. If i find the intersection of line exterior and polygon boundry, what will be the graphical representation of both objects intersection.. its my concept.. ...
6
votes
3answers
832 views

Retrieve polygon smallest MBR

I have a postgis table containing polygons. I want to transform my polygons to 4 points polygons : retrieve the smallest MBR. Here comes an illustration of what I want : My original polygon is ...
9
votes
1answer
6k views

How to create a script tool that will create a copy of a feature class and offset it by a given distance? (arcpy)

I want to duplicate a polygon feature class and offset all of the polygons by about 10 feet in both the x and y directions. I asked if there was any way to do this last week, and I was informed that I ...
-4
votes
1answer
138 views

vector with epsilon [closed]

if there are two points p1 and p2.and vector of both is ab .. now if i say -1 < ab < 1 condition true than return F.. is that mean by points p1 and p2 intersect to each other...?
2
votes
2answers
133 views

MMP of geometries

MBR is used for extent of geometries.. then what is the use of MMP.. is it for visualization the objects?
18
votes
4answers
2k views

Generalisation Strategies for Building Outlines

I have a dataset of building footprints vectorised from a raster dataset. The dataset is currently just a vector representation of the raster data. I would like a polygon dataset that only has ...