A coordinate-based data model that represents geographic features as points, lines, and polygons.

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14
votes
7answers
5k views

Nearest neighbor between a point layer and a line layer

I've asked this question several times on stackoverflow and irc between #qgis and #postgis and I also tried to code it or implement it my self in postgis with no real answer. Using programming (most ...
0
votes
1answer
144 views

Sum of values within a buffer polygon

I need to do the following in QGIS and hope so much anyone could help. I have a vector layer with points. Each point represents a firm with the number of employees in the attribute table. I want to ...
2
votes
1answer
84 views

graduated labels in QGIS

I've searched on Google but haven't found an answer. The QGIS Dufour GIS provide an enhanced vector-styling interface but is it also possible to graduate the labels like it is possible for the ...
1
vote
1answer
48 views

what is the alternative of setZoomLevel in vector based map

It is commonly used to generat map tiles at a certain scale and re-organize them for web map on pc. For example googlem map, and bing map. Then user will use the setZoomLevel(int level) or something ...
1
vote
0answers
215 views

Updated: Openlayers Vector Layers with Google Map Base Layer (via Grid): Vectors Stick but can't get correct resolution/projection

Revamping this question instead of opening a new one. Previous issue: vector layers were not "sticking" to the map, so when you would zoom in or out the vector layers would "come out" at you. Note ...
0
votes
0answers
70 views

QGIS: How to reverse vertex ordering in polygons

I am working with an Oracle spatial connection in QGIS through which I am accessing and editing a vector layer. I find that when I edit a geometry, the vertex ordering is reversed (to clockwise in the ...
0
votes
1answer
47 views

Generating a polygon tile index from multiple vector datasets

OK. well this is silly, in that there is no way it should be as difficult as it has been for me to find information regarding how to generate a polygon tile index from multiple vector (contour) tiles. ...
0
votes
0answers
65 views

How Can i create a Vector layer from selected features qgis

In my qgis plugin i select dynamically features from a Vector layer. and currently i create a new layer from selection on combining all feature into a new feature: theField = QgsField self.theString ...
0
votes
0answers
57 views

how do I add attribute features to an attribute table which already exists?

Using Verson 2.0, downloaded as normal. I have an ESRI shapefile of my road map for 2006. I have a paper map of roads for 1969. I want to see what roads have been built between 1969 and 2006 (none ...
3
votes
2answers
120 views

Comparing 2 polygon shapefiles for differences [duplicate]

I have 7 shapefiles, each representing a year, all containing lots of polygons (c. 500,000). My aim is to take any 2 of them and compare how they have changed in terms of size and shape of polygon. (i ...
4
votes
1answer
74 views

Suggestions for vector format for contour map

I've been trying to create a contour map of a DEM and I've been running into some technical problems. I want to avoid artifacts, so I'm using a DEM of the entire area. This means the size is rather ...
0
votes
0answers
73 views

Calculating vector statistics in GRASS

I have a points layer, each of points have an year attribute and I want to count how many points in each year. I use GRASS-GIS and its v.univar function: v.univar -e map=mod14_hmao column=year ...
1
vote
1answer
53 views

OpenLayers, Get clustered point's val

I'm working on a map with WMS overlays and a lot of markers, my problem is when I try to calculate the average of points clustered, I've found how to differentiate the behaviour and the label text ...
1
vote
1answer
39 views

Decoding Mapbox grid response

Can anybody give me insight into the grid json structure that Mapbox returns for use with overlays on tiles. What is the significance of !,#,$? Thanks in advance.
1
vote
0answers
159 views

Line segment connectivity analysis in FME

I have a set of line segments, all of them snapped at the endpoints: As seen in the above image, the line segments appear in groups (4 in this example). Question: I would like to determine which ...
2
votes
1answer
613 views

OpenLayers Vector Layers: adding and removing features VS. redraw/refresh

I am currently using addFeatures and removeAllFeatures in my code to get the desired results and this is working OK. However, I have been asked to ensure that the vector layers are not being ...
0
votes
0answers
39 views

Newbie, I want to make a map that shows something along the lines of the following:

What is the average income for housing units (middle, mixed, family, etc.) within a 2 mile radius of parks for the City of Anaheim? or What is the average number of parks within the 1/2 mile radius ...
1
vote
2answers
64 views

Splitting discontiguous vector feature in QGIS

I'm a QGIS novice. I'm trying to correct a map of Europe in QGIS, and it's incorrectly assigned Corsica to Germany. I can't seem to split Corsica off of Germany because when I use "split features" to ...
0
votes
0answers
61 views

How to change Split Vector by Attribute to produce files with attribute values as file names?

Using: QGIS 2.0.1 I am trying to separate a large fauna point .shp file into many shapefiles based on each species' unique name attribute (i.e. by "SCI_NAME" field)??? I am currently using "Split ...
1
vote
1answer
160 views

How do I create rendered vector field in qgis

Perhaps I am misunderstanding the "vector field renderer" and "VectFieldCalc" plugins, but I have no idea how to make a vector field of arrows, with directions and magnitude. I have the data loaded ...
2
votes
3answers
121 views

Ordnance Survey 1 km Grid

I am wanting to get a copy of the OS 1km Grid layer. I have found these previous questions: Ordnance Survey grids - download or generate? and Ordnance Survey Grids But neither provide the ...
5
votes
2answers
181 views

How to download Leaflet vectors in GPX format?

I would like to use the leaflet.draw plugin to allow users to digitize vectors on the map. At the end the data should be downloadable as a GPX-file. Is there any sample that shows how this can be ...
0
votes
0answers
37 views

GRASS v.to.rast.attr returning null values

I am having a problem converting vectors to rasters in QGIS. As there is no tool where you can directly set the pixel size (instead of the height and width of the new file) in QGIS 1.8 (the version I ...
5
votes
4answers
7k views

Customizing Popups in Openlayers

Is it possible to customize the shape of popups in OpenLayers? For example, I am creating a pop-up using the following approach: var popup = new OpenLayers.Popup.FramedCloud( "popup", ...
6
votes
2answers
273 views

Convert points to lines with Python GDAL

I have a dictionary with points. The points are derived from a raster (see image below). The points are not sorted and are not in order. The dictionary looks for example like this: pointDict = {0: ...
4
votes
2answers
112 views

Problem overlapping shapefile and vector in R

I want to plot a shapefile over a raster file in R but I can't make them overlap perfectly: the raster appears to be rotated of few degrees counter-clockwise. Is it a problem with the projection? ...
1
vote
1answer
67 views

Openlayers Vector Event Popup with Textbox

The Openlayers map here: http://www.dassh.ac.uk/demonstrations/valmer/demo5.html has an event to add a vector layer, plus creates a textbox on the page below. Ideally I'd like the click event to add ...
-1
votes
1answer
309 views

Retrive data from database in openlayer GIS

i am using this code but it shows nothing, whats wrong with this code. <!DOCTYPE html> <html lang='en'> <?php $conn_string = "host=localhost dbname=postgis_21 user=postgres ...
2
votes
0answers
207 views

GDAL polygonize lines

I have a raster file containing roads (left image). I polygonize the raster file with GDAL (see the script below). In the end I like to have vector lines. However GDAL only gives me something like ...
5
votes
4answers
2k views

How to calculate polygon length and width using open source GIS?

How can I calculate the length and with of polygons using open source tools? By "polygon length" I mean the length of the longest line within the polygon (update: to be correct, I just need the ...
4
votes
0answers
82 views

Convert Graphics to Vector in QGIS

I am wondering if there is a way to convert a graphic produced from symbology in QGIS to a vector layer (ie: shapefile). I have a point layer with bearing direction in the attribute table. Following ...
1
vote
1answer
105 views

Openlayers Vector Layers eventListeners: how to specify different data without defining multiple layers

I have a map. It has two origins, and two destinations. The code for one origin is here: vectors_origin = new OpenLayers.Layer.Vector("Origin", { eventListeners:{ ...
0
votes
0answers
98 views

How to convert Raster to polygon in MapInfo?

I wanted to convert Raster data to point data in MapInfo.Does there any tool to convert? can anyone help me?
1
vote
1answer
60 views

Raster Data to Polygon [closed]

I need to "translate" raster information to a set of polygons. The raster to polygon tool will not work. I created a fishnet with the same resolution of the raster and converted it to polygons. I now ...
6
votes
3answers
239 views

Create interactive map with no server

I have managed to build a great web mapping application using tiles created from GeoWebCache and a custom gridset, but I now need to add an overlay to the base maps. The only interactivity I need is a ...
2
votes
1answer
50 views

How to change layer transparency without changing border lines?

I have a raster image of elevations. I have added a vector shapefile that contains local political divisions. I want to keep the elevation colors, but I want to keep the black lines representing the ...
0
votes
2answers
380 views

Using OS Mastermap SLDs in QGIS

In an answer to a question asked by @Canningmister, @tjmgis posted an excellent answer Styling OS Vectormap Local in QGIS? about making OS SLD files work in QGIS. As an amateur user who uses QGIS to ...
2
votes
0answers
63 views

How can I improve the resolution of a vector grid made in north pole stereographic projection?

I've been struggling with this for a while and wondered if someone could lend a hand. I have a map which already has sampling points from centroids in a 35x35km grid that was created in north pole ...
1
vote
0answers
49 views

How to auto-fill a new point vector in a vector layer?

When I work in-situ I manually add points in my shape-file. I would like that when I add a new point some attributes would already filled with values calculated programmatically. E.g in my first ...
2
votes
4answers
143 views

High resolution and high detail vector GIS coastline product needed

What is the absolute best vector GIS coastline product available globally? I know of a great product for Africa (page 13 of this PDF ...
2
votes
2answers
85 views

How to overcome the layer limit on OSX?

I am trying to add many layers to a project in QGIS. After adding approximately 80 layers, QGIS returns this error: "not a valid or recognized data source". There is nothing wrong with the shapefiles ...
25
votes
5answers
39k views

What are Raster and Vector data in GIS and when to use?

What are raster and vector data in the GIS context? In general terms what applications, processes, or analysis are each suited for? (And not suited for!) In answering someone's question today, I ...
0
votes
0answers
38 views

grass plugin in QGIS all of sudden not working as expected

The previous week I was able to use the grass scripts in the QGIS 2.0.1 Dufour toolbox, but today they do not seem to be working. I am not sure where to place a '-c' which was a solution to the same ...
0
votes
2answers
123 views

MapServer: How to display and style a Text layer?

I'm trying to display a text layer using MapServer, but I'm kind of confused how to get it to display properly. When opening the .TAB file in a GIS application (in this case, MapInfo Profressional) ...
2
votes
3answers
2k views

Openlayers get coordinates from polygon

please could someone help me and bless me with an example of how to get coordinates from a polygon in OpenLayers?
4
votes
4answers
738 views

How to get vector data from OSM to use in QGIS?

How do I get data from OpenStreetMap which I can then edit in QGIS layer by layer? What is the best OSM output and what / how do I get to a suitable input for QGIS? OR...is there another appraach to ...
1
vote
0answers
55 views

Problem in removing dangles in road network [closed]

Im using qgis2.0 , In a given road network i have to remove dangles, for that what should be the tolerance to be added generaly. please help me resolve this issue
0
votes
1answer
90 views

How to increase symbol size of polygons when zoomed out?

I have many small polygon scattered. How do I increase size of polygons when zoomed out in qgis? As seen in the image the symbol appears to be lost when I zoom out. Note: I have created a thematic ...
0
votes
0answers
47 views

Using Raster Data in a Vector Layer's table in QGIS 2.01

I have a vector layer containing point data representing floor levels. The attribute table contains: Easting Northing Floor Level I also have several water surface levels representing the ...
2
votes
2answers
64 views

cutting and extending one polygon layer in function to the other layer boundaries

I'd like a methodology that can edit my vector layer, extending and cutting the features in the polygon layer "cap_agricola" within the boundary layer "sp_edr", I would like to solve this problem in ...