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

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3
votes
2answers
188 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
99 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
74 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
92 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 ...
0
votes
0answers
49 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 ...
2
votes
1answer
2k 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 ...
1
vote
2answers
190 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
106 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 ...
0
votes
1answer
2k views

How to clip a line layer based on polygons with QGIS?

I have a line layer and a polygon layer. Both files have the same SRS. I want in a new shape file only the lines covered by the polygons. I tried in QGIS the Vector -> Geoprocessing -> Clip ...
2
votes
3answers
273 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 ...
4
votes
1answer
231 views

Loading a multipoint shapefile in R

This issue has only been raised in the community once, two years ago, to the best of my knowledge. I think it's high time to raise the issue again! readOGR, from the rgdal package, cannot handle ...
0
votes
0answers
79 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 ...
0
votes
2answers
377 views

How to Resolve Inconsistent OpenLayers vector position Over Google map [duplicate]

I have an OpenLayers map with a Google base layer and an OpenLayers vector layer on which people can draw their own bounding boxes using the DrawFeature control. I have found that, as you zoom in, ...
6
votes
2answers
397 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
154 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
152 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
763 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 ...
4
votes
1answer
460 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 ...
4
votes
0answers
122 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 ...
0
votes
0answers
176 views

How to convert Raster to points 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
81 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 ...
1
vote
1answer
294 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:{ ...
7
votes
3answers
406 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
131 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 ...
1
vote
1answer
52 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.
0
votes
2answers
647 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
95 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
57 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 ...
3
votes
4answers
253 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
1answer
268 views

pyQgis in stand alone script, vector loading error

I am trying to use the Qgis functions in a stand alone Python script. I m running Mountain Lion OS, 2.7 Python & the Qgis 2.0.1 Dufour. My main problem is that I cannot get started - I cannot ...
0
votes
0answers
42 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 ...
1
vote
1answer
80 views

map can only have one feature, after user click

I'm using openLayers 2.13.1. I have a map wih a vector layer and Editing tools. I want the map to have only one feature even if the user keeps adding. So I want the new feature to automatically ...
1
vote
0answers
68 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
2answers
225 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) ...
7
votes
2answers
427 views

What does vector tiled map mean?

I'm working on an application that renders geoJSON into OpenLayers map. The idea is about not having PNG images downloaded from external services (OSM or Bing) but having geo information in geoJSON ...
0
votes
0answers
64 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 ...
1
vote
0answers
50 views

Delete polygon underlap?

I am editing a layer in QGIS with severe polygon overlaps. Is there a way to delete the underlapping portions (i.e. the invisible parts) using QGIS? If I import the layer into GRASS using the ...
1
vote
2answers
245 views

Decrease resolution of vector shapes (polygon) i.e. reduce size and number of points in outer ring

I'm trying to get a kmz export down to less than 3 megabytes and am wanting to do so by reducing the number of points in my polygons' outer rings. I've seen this concept in action when it comes to ...
1
vote
1answer
418 views

Check if feature is selected (Openlayers)

I wonder if there is a way to check whether a pointfeature (OpenLayers.Feature.Vector) is selected. I read the API, but didn't find any solution. Any idea?
1
vote
0answers
98 views

OpenLayers - Features in cloned layer changes style with original feature

Please help! My situation is that, I clone() a "newLayer" from an "oldLayer" with its features. Both of them seems correct at first. But then when I tried to change the style of "featureA" in the ...
3
votes
1answer
155 views

Converting map image to GIS

I’m very new to GIS, and I’ve been reading a lot of manuals and information, but I thought I’d ask a couple of questions here. One of my major hobbies is drawing maps of a completely imaginary ...
1
vote
1answer
195 views

How To Show Percentages By Coloring Polygons in QGIS?

I am trying to produce a map with QGIS that has counties shaded according to the percentage of people born in a US Region. For example, counties with a high percentage of people born in the South ...
2
votes
1answer
101 views

heat map of density ratio of 2 layers of points

I have 2 vector layers of points: one with a point for each house in the city (thanks to osm.org), roughly equivalent to population one with a point for each case of cholera in the city I'm trying ...
3
votes
1answer
227 views

How to sum up all field values in QGIS modeler

I am building a model to generate two zones around a point, a 250m-buffer, and a ring of 250 to 1000m, where i recalculate values from an other layer according to the intersections share. The purpose ...
0
votes
0answers
115 views

Identify segments that share a last vertex with the first vertex of selected segment

This has been marked as a duplicate to Connecting line features and determining the length of the longest line but I believe there are some subtle differences. And to be honest I'm not an advanced ...
1
vote
2answers
383 views

OpenLayers: WMS layer above select-controlled vector layer?

Is it possible to display an image layer (WMS or Image) above a vector layer with activated SelectFeature control in OpenLayers? The image layer (radar returns) contains only sparse, semi-transparent ...
5
votes
1answer
149 views

LiDAR Feature extraction specifications/standards

I have vector data representing forests/trees/buildings that have been automatically extracted from LiDAR data. I am looking for specification/guidance for LiDAR derived products, or any standard for ...
2
votes
1answer
282 views

Possible workflows for shaded relief representation as vector

I am looking for a good workflow on how to represent relief on a map as vector (e.g. for further processing in Adobe Illustrator or Inkscape). My inspiration is the present google maps at zoom level ...
1
vote
2answers
107 views

QGIS point sampling tool really slow for polygons?

I have a large field of randomly distributed points (100,000 of them to be precise), and I'd like to get values for a variety of raster and polygon coverages for each point. I've been using the QGIS ...
3
votes
2answers
316 views

How to calculate distances between addresses and cities and coast line?

I am totally new to GIS, and so I apologize if my question is not clear enough. My basic problem is the following: I have about 160,000 Danish addresses with longitude and latitude for each address. ...