(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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13
votes
5answers
411 views

What in-depth spatial database systems tutorials exist?

Is there a good tutorial that explains in depth the internals of a GIS and a spatial database system such as PostGIS with examples and without any background assumption? I'm specifically looking for ...
2
votes
1answer
196 views

How to modify the coordinates of a SHP geometry using Geotools?

I have a shapefile with some polygons. I would like to change the height for this elements using Java. The rest of the attributes should be the same. I've thought using GeoTools but I haven't found ...
0
votes
1answer
78 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 ...
5
votes
1answer
376 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 ...
2
votes
1answer
176 views

Calculating area [closed]

I have a polygon layer. I toggled to edit mode. I added a new column, while number (integer) and called it "area". I then use the field calculator - geometry - $area to populate the polygon area for ...
4
votes
1answer
553 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 ...
0
votes
1answer
108 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 ...
1
vote
1answer
75 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
0answers
211 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) ...
2
votes
1answer
40 views

How to generate features to test different implementations of LinearRing?

I have some code that throws the following exception: Points of LinearRing do not form a closed linestring and I want to check if my code is calling this correctly by supplying some features that ...
6
votes
3answers
2k 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" ...
1
vote
1answer
141 views

How to fix buffer selection issue in ESRI ArcGIS Javascript API and LGIM applications

I had strange LGIM application behavior where the map spatial search did not highlighted the parcels within the Geometry Buffer. What could be the possible reasons? LGIM stands for the Local ...
21
votes
1answer
700 views

Space filling between random 2D lines

Consider a region (2D) filled with lines randomly (following Figure). We are interested in filling the empty spaces between lines including four boundary edges in a way: 0- maximizing the size of ...
5
votes
2answers
810 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". ...
14
votes
3answers
2k views

How to find the maximum-area-rectangle inside a convex polygon?

In this post we are looking for algorithms / ideas on how to find the maximum-area-rectangle inside a convex polygon. In the following figure, numbers are the areas of the fitted rectangles. As shown ...
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 ...
4
votes
0answers
246 views

What traits identify 2D, 2.5D, 3D geometries, and how can you convert downward, such as from 2.5D to 2D?

In answering this question, posed by @Burton449, I came to realize I don't have a definitive grasp on what distinguishes 2D, 2.5D, and 3D geometries. I certainly realize Z/elevation values are ...
2
votes
1answer
305 views

Map projection lat, lon to pixel?

I'm trying to find the concave hull of a lat, lon pointset but when I project my points on my map it doesn't look like expected. I've tried a lineare projection and a spherical projection. My data is ...
1
vote
2answers
145 views

Distance between latlongs varies in different projection systems?

I have shapefiles with correct projections. The SRS is EPSG 32735 (WGS 1984 UTM 35S) Now, I have these two coordinates from this projection system: (31.3751,-23.4388) and (31.3779,-23.4355). ...
1
vote
1answer
802 views

PostGIS and geometry column

I have a csv table. Each record includes a start node (lat1,lon1) and an end node (lat2,lon2). I have already imported the .csv into Postgresql 8.4. Now I would like set the geometry column. I tried ...
1
vote
0answers
271 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 ...
1
vote
0answers
30 views

PostGIS. Obtain the rotation between two equal Geometries

I've got two features with the same drawing (poliline) but one is rotated relative to the other. I would like no know in PostGIS the rotation between the two geometries to apply this rotation to a ...
2
votes
1answer
301 views

GML - Multi-geometry validation

I'm doing the test to introduce multiple geometry in a WFS service using GML. For now the simple geometry is functional, but I still have some bugs with multiple geometry. I think it may come from my ...
1
vote
0answers
140 views

Problem import shapefile in PostGIS database

I am having a Polygon shape-file. When I try to import this shape-file in PostGIS some of the attributes in Geom Field is found empty. But in attribute table when I select that polygon It is visible ...
2
votes
1answer
147 views

How to convert a line to points?

I'm working with QGIS and I want to convert a line into many points, does someone know how? Thanks.
7
votes
3answers
12k views

Create a geography/geometry column from x and y fields - SQL Server 2008

Hy guys, I'm new in SQL Server 2008 and I hope you will understand my question/need. Thus, I have a table which contains 3 fields (Name, Lat and Long) in my data base (spatial). I want to create a ...
5
votes
1answer
297 views

Can ArcPy 10.1 be used to generate true curve elliptical polygons in a file geodatabase?

As background, this question arose from trying to answer a question on How to generate overlapping polygons from lines output from Table To Ellipse tool? Using the ArcMap GUI it is very easy to ...
0
votes
0answers
82 views

How to find the list of TMC codes by region or by geometry polygon?

Can you please suggest a way to find out all the TMC (Traffic Message Channel) codes by region or by Geometry polygon values. My area of interest : USA
0
votes
0answers
291 views

Publishing PostGis table using GeoServer REST returns error when geometry column is NOT named “geom”

I tried publishing an existing PostGis table with geometry column named "wkb_geometry" to Geoserver using its REST API. I used the following command: curl -v -u admin:geoserver -X POST -H ...
16
votes
2answers
4k 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: ...
1
vote
2answers
363 views

Convert 3D WKT to 2D Shapely Geometry

I have the WKT of many linestrings which contains three dimensions, however my script only requires a two dimensional linestring and I therefore want to discard the third dimension. My current code, ...
2
votes
1answer
708 views

How to convert Geometry type column to degree Minutes Second in SQL Server 2008 R2

I have shape column of type geometry and I want to convert X and Y coordinates into Degree Minutes Second format using SQL query and i am using sql server 2008 R2. Currently I got Lat and long using ...
2
votes
1answer
174 views

Center point approximation of a polygon

I would like to get a center point approximation of a set of polygons so I can do a NN lookup to use for assignment instead of a point in polygon query. Lets say I have this set of polygons: I ...
1
vote
1answer
397 views

SQL 2012 - How can I convert MultiLineString to Geography?

I have a Geometry LineString that I wish to convert to Geography. Since the Geometry isn't valid , When I use MakeValid on it, SQL convert it to MultiLineString and than the Geography creation is ...
2
votes
3answers
391 views

Polyline selection of features with angle turns up to a specified angle

I'm looking for an automated way to select line features that have specified angle between vertexes. That in order to check water mains layer -steel pipes can have only 45 or 90 degrees turns and I ...
0
votes
1answer
220 views

SetGeometry problems when using python/ogr

So i am trying to use the difference function and i pretty much create the new file i want but the Geometry is empty. No error is produced. any help would great! Thanks. #!/usr/bin/env python import ...
1
vote
1answer
503 views

What to do if PostGIS gives error that “geometry requires more points”?

I have a .TAB file. I convert it to ESRI(shp)-->sql and insert it into database. Using PostGIS when I want to convert the data into ESRI file, it shows an error: geometry requires more points ...
0
votes
0answers
160 views

Openlayer seems slow when zooming / panning on vector (geometry line) from geojson. Why?

I have a layer with 7 lines . when I zoom on some of the lines , the maps seems to be very slow. I thought it might be because I bring a lot of points to the client (that represents the line) aa ...
2
votes
1answer
116 views

Which fields are standardized to describe a ShapeFiles feature?

I would like to store data into a database which is available here either as JSON or as ShapeFiles. The JSON looks something like this: { "type": "FeatureCollection", "features": [ { ...
0
votes
1answer
1k views

Trying to convert geometry to geography keep failing in MSSQL 2012

In MSSQL I have LineString in Geometry type. When I try to convert it to geography using : ...
2
votes
1answer
77 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 ...
1
vote
1answer
106 views

Insert geometric data to a column from coordinate values in double precision

Screenshot of database http://wp.me/aIW9p-i0 For table “households”, I want to create two new columns: 1) “Geom”, data type – geometry; 2) “WKT”, data type ‐ text; I am intending to do the following ...
2
votes
2answers
278 views

How can I create a multipoint geometry in QGIS?

I've got a Spatialite layer in QGIS with geometry type MULTIPOINT. Now I'd like to add some data in this table in the 'usual' way, so by doing multiple clicks in the map (e.g. left-click, left-click, ...
3
votes
1answer
309 views

Programmatically manipulate GPX data

I need to do the following in Python open OSM & GPX files (I have packages for this) transform points from GPX (like stick a track to roads) calculate the results (distances, cumulative ...
3
votes
1answer
147 views

How can i topologically sort 2D triangles and put in an array?

I have a set of 2D triangles in a Geometry array which together forms a connected strip when placed them according to edge adjacency. However, in the array they are not in topological order based on ...
3
votes
2answers
1k views

How do I get that polygon from Javascript ArcGIS API?

I would like to have a user draw a Polygon (or Line) onto a web map with the Javascript ArcGIS API drawing tools. For the life of me I can't figure out how to pull that polygon from the client and get ...
1
vote
2answers
619 views

Why do I get wrong length using STLength on MultiLineString?

I have 2 MultiLineString representing the a route (first is driving there and the second is the return way) . MULTILINESTRING ((34.787315938035292 31.318235314177119, 34.788431415005249 ...
1
vote
0answers
82 views

Why is my linestring not valid ? was recorded from GPX file

I have a linestring that was built from points from GPX file. I've insert it to sql as geometry and when I try to run funcs on it (like STStartPoint ) I get error that line isn't valid and I need to ...
2
votes
1answer
350 views

How to perform a cascaded combine from python script in QGIS?

I'm working with a large dataset, and I need to be able to combine up to 400,000 polygons. I have been using the QgsGeometry::combine(QgsGeometry* geometry) function and simply looping over all ...
4
votes
0answers
802 views

Finding the “center of gravity” of multiple points where points have unequal weights [closed]

I'm trying to reduce a set of lat/lons (each with it's own weight) into one lat/lon that is the center of mass of all of the points. however when I map the results the average point falls no where ...