(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
1answer
512 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
278 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
457 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
7k 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
158 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.. ...
7
votes
3answers
900 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
7k 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
134 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
3k 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 ...
17
votes
3answers
4k views

Find tunnel 'center line'?

I have some map files consisting of 'polylines' (each line is just a list of vertices) representing tunnels, and I want to try and find the tunnel 'center line' (shown, roughly, in red below). I've ...
3
votes
1answer
573 views

Is it possible to figure out which “Path”(PointCollection) is clicked on within a PolyLine?

I am using ArcGIS WPF's Polyline to plot several lines (PointCollections). Adding a Path(PointCollection) looks something like this. PointCollection collection = new PointCollection(); PolyLine ...
12
votes
5answers
835 views

Simulating the expansion of polygon features

I've got what I'm hoping will be an interesting question. I'm working on an assignment for an intro to GIS course that uses some Gulf oil spill data to introduce common vector-based spatial analysis ...
12
votes
4answers
2k views

Comparing two Digital Elevation Models (DEMs) from LAS files?

I have two Lidar las files, one is original let's say with X points. And the other is copy of the first las file but with Y points, where Y is less than X. Now, I want to compare how the Digital ...
4
votes
1answer
1k views

Clipping a SqlGeometry

I have been messing around with the SqlGeometry in the Microsoft.SqlServer.Types namespace in .NET, and have been rather impressed. Can anyone provide me with an example of how I could clip a ...
10
votes
2answers
386 views

Tools for importing historical maps into modern GIS systems

What tools exist to derive geometries for use with modern GIS systems from older scanned maps? I am referring more to libraries that generate actual data rather than present an interface for manually ...
6
votes
1answer
682 views

Help simplifying multipolygons in geodjango

I have a few multipolygons that have several hundred points in them. I'm looking to create less complex "thumbnails" polygons. Naturally I'm attempting to use the simplify method, which is supposed ...
69
votes
14answers
23k views

What are Definition, Algorithms and Practical Solutions for Concave Hull?

Convex Hull A convex hull of a shape is defined as: In mathematics, the convex hull or convex envelope for a set of points X in a real vector space V is the minimal convex set containing X ...
9
votes
2answers
1k views

What are the implications of invalid geometries

I've imported some data in a Postgis database and some of the geometries are reported invalid (ST_IsValidReason reports self-intersection or ring self-intersection). The queries I am performing don't ...
17
votes
2answers
5k 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: ...
6
votes
2answers
1k views

Unions of polygons (Postgis ST_UNION for Geography type)

I am looking for a function that will return the intersection of 2 or more polygons (geography type). I am aware of ST_UNION, ST_COLLECT but it works only for geometry type. Any tip will be really ...
3
votes
3answers
917 views

Open .NET implementation of the OGC Geometry Object Model from Simple Feature Access 1 specification?

I am looking for a .NET implementation of the geometry object model described in OGS's Simple Feature Access, Part 1 specification. Preferably lightweight. I don't need WKT support, just the ...