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

learn more… | top users | synonyms

1
vote
2answers
50 views

How to show average walking distance to closest point in census tract in ArcMap?

Given a map layer of point locations, and a second map layer of census tract polygons for the same area, how would you create a map layer that shows the average walking distance to the closest point ...
1
vote
1answer
34 views

How to crop a vector shapefile according to raster?

I am trying to clip a vector shapefile- points according to a DEM in QGIS. I used GDAL function and polygonized the DEM. Then I ran the Vector-Geoprocessing tools-clip in order to crop the vector data ...
2
votes
1answer
30 views

Extract all raster cells outside a polygon

How does one perform the very simple task of extracting all raster cell values outside a polygon? I've been looking through QGIS for hours with no solution to this simple problem.
2
votes
1answer
32 views

OpenLayers - cannot set layer opacity

I have the following problem: by default, you can simply change the opacity of layer by writing for example: layer.setOpacity(0.3); But when I add it to my map SelectFeature controls, my layer is ...
1
vote
1answer
33 views

Deleting vector lines beyond image extents using QGIS?

I am using QGIS 2.2 I have one vector line layer (roads) that stretches beyond my base image (see below). I wish to have the roads "clipped/trimmed or deleted" right at the edge of the image's ...
2
votes
1answer
94 views

Memory Vector Layer Corrupted?

I was working with a large data set that had data for roads, rivers, railways, etc. all together so I decided to break the different data out so I could label it differently on the map and check each ...
1
vote
0answers
34 views

Vector layers without geometry in QGIS?

Using QGIS, I have set up a couple of automated layer additions via the toolbar. After adding geometry in each respective layer (point, lineString, polygon) and saving changes to the layers, the added ...
1
vote
0answers
17 views

Vector Layer Symbol (ism) properties?

I would like to streamline the render of a polygon grid vector layer as a simple line (no fill) via Python coding. I am I bit confused by the implementation referenced by the API. Is it possible to ...
0
votes
1answer
75 views

How to perform an attribute-weighted sum of multiple polyline features from a single vector layer?

I have a shapefile of ~8000 polyline vector features representing traffic journeys on road routes. Each has an attribute representing volume of traffic for that journey. The routes are all generated ...
1
vote
1answer
67 views

How to batch-process attribute tables in QGIS (or GRASS)?

I'm using GRASS 6.4.3 in Linuxmint 16. I have a bash script for GRASS which I use to process almost 300 raster files. The script first imports some raster files (r.in.gdal), then does some ...
1
vote
0answers
79 views

How to create a rainfall raster from rainfall contours?

I downloaded a free rainfall data from the Philippine GIS Data Clearinghouse (PhilGIS) which are vector lines. How can I extract the data points from this? I want to extract it because i will be ...
1
vote
0answers
36 views

Polygonize Missing Polygons

Polygonize is not capturing all of the pixels in an image that has been converted to 0s & 1s. The pics below show -original geotif -geotif recalculated to 0s & 1s -polygonize output As the ...
4
votes
0answers
58 views

How to compare two sets of points in QGIS?

I have two point layers with XYZ data; one set are points measured in the field and the second set is a Lidar data set. I want to check the accuracy of the Lidar in comparison to the measured data. ...
0
votes
0answers
51 views

Polygonize only pixel values of 1 from a raster

I have a raster mask that I have created in QGIS (2.2.0) that consist of 0, 1 and nodata values. I would like to end up with a polygon dataset that consist of only the value of one pixels from this ...
0
votes
0answers
63 views

How to create a vector layer from a GeoAlchemy2 query?

I'm currently developing a QGIS plugin where I mapped a PostGIS database via GeoAlchemy2. I wrote a function that returns results from a GeoAlchemy query but have no idea how to create a vector ...
2
votes
3answers
255 views

Creating a Slope Map Using Contours

I am trying to create a slope map. I have many contour elevation files. I tried to use the slope tool in Arctoolbox, but it calls for raster files and I'm working with vector data. Any help with this ...
0
votes
0answers
32 views

QGIS Rasterization of points

I have a point vector layer and want to make it a raster. Trouble is that many points are very close to each other, so unless I specify a very small resolution of the raster cells, likely several ...
0
votes
1answer
51 views

Process to georeference corners of vector file?

I am new to QGIS and trying to wrap my arms around it so please bear with me. I have vector files (DXF) that I need to add back in the georeferencing. They were edited with Illustrator so I loose ...
0
votes
0answers
10 views

Adding (ir?)regular vector points

I run 2.0 qgis. (I am quite the rookie) I would like to add a point layer which is regularly spaced every 5 metres along the x-axis, and regularly spaced every 1m along the y-axis. I cannot seem to ...
0
votes
0answers
43 views

USA MSA/City/County with SImplest Border in JSON

I deal with a lot of poloygon-related JSON representing US places regularly. One thing that could make reading JSON with my eyeballs easier is having a short list of US places whose borders have ...
0
votes
1answer
88 views

Raster and vector layer in the same CRS don't match

While adding multiple raster and vector layers (and setting them all in CRS WGS84) in QGIS 2.2, they don't seem to overlap. Interestingly enough, only raster files overlap between each other, the same ...
2
votes
4answers
94 views

How to set a minimum point snap distance?

There are two points: A and B. I need to snap any points within a 65 m search radius (blue buffer) of point A. However, the snap distance of B needs to be exactly 5m apart from A (i.e. located ...
0
votes
0answers
52 views

Can I create a cross section from points along a line without using a DEM in QGIS?

I have a set of points perpendicular to a river and would like to present a cross section of them. Like a simple graph in Excell for example, with Z as y axis and distance along the line as the x ...
1
vote
1answer
64 views

Calculating percentage of polygons within specific areas using ArcGIS for Desktop? [closed]

I have a parcel layer and I am trying to determine the percentage of each parcel that falls within specific zones. I tried tabular intersect but it just returned an empty output. I'm using ArcGIS ...
3
votes
1answer
68 views

Comparison of vector file formats

Does anyone know of a chart or table that would explain the benefits / shortcomings of the different vector file formats, eg. .shp, .gml, .kml, .gdb. It seems that ESRI shape is still quite prolific, ...
0
votes
1answer
56 views

How do i rescale feature classes of different scales for intersect analysis?

before I intersect 2 feature classes of different scales (e.g. 1:200,000 soil map and 1:25,000 land use map), should I rescale them like how u would resample raster datasets to the same resolution ...
0
votes
0answers
33 views

QGis road graph plugin can't be configured

I am using QGIS 2.2.0 Valimera on a Windows 7 ultimate 64 bit version. I want to calculate the shortest path on a line layer (OSM street layer) with the road graph plugin. The settings option to ...
0
votes
1answer
69 views

Difference in vector / raster area measurements

I'm comparing raster and vector distance zones. So I created a line, calculated the Euclidean distance, and reclassified the raster to two zones: from 0-10m and 10-20m. To compare it with vector ...
0
votes
1answer
40 views

how can we convert vector data to raster data in geotools

In my project iam able to open and save shape file. I want to convert this vector data to image format as a tiffimage plese help me the procedure to do the same.
0
votes
0answers
40 views

rasterize table polygon postgis 2.1

I would like to rasterize a postgis 2.1 polygon table, but I don't undersand how to create the SQL function syntax for ST_AsRaster. My vector table has 3 fields: gid, recharge, and geom. The SQL ...
0
votes
0answers
15 views

QGIS merge selected features tool malfunctions due to geometrical errors [duplicate]

The issue occurs using the 'Merge Selected Features' tool when there are geometrical errors in the features (not all are picked up by the 'check geometrical validity' tool). In 2.2 Valmeria, the ...
0
votes
0answers
57 views

OpenLayers DrawFeature Vector parameters

"Dear all, in my map application I am using a Vector/DrawFeature approach like this: var refresh = new OpenLayers.Strategy.Refresh({force: true, active: true}); var proj = "EPSG:900913"; var ...
0
votes
0answers
53 views

gdal read whole geotif band into vector

i have another c++ GDAL question. I try to read alle elevation data out of an GeoTiff file into a c++ vector so that i can get elevation at x,y like this: vector[x][y]. I also like to use this data to ...
0
votes
0answers
51 views

OpenLayers.Layer.Vector and BBOX

i configured this on my client page var kmlLayer = new OpenLayers.Layer.Vector("KML" ,{ strategies: [new OpenLayers.Strategy.Fixed(), new OpenLayers.Strategy.BBOX()], protocol: new ...
0
votes
0answers
9 views

dividing a line vector road in QGIS [duplicate]

how do I divide a road, say of 10 km length which I have digitized from Google Earth, into regular intervals of 1 km? The roads are not straight and have been digitized around ponds in human dominated ...
1
vote
1answer
28 views

Load a vector only for a specific zoom

I have a map with 4-5 vectors. At the beginning, the loading of the web application is very very slow, but was fine before I've added a new one vector, which is used only for little zooms. Is it ...
0
votes
0answers
32 views

The difference when querying raster and vector

Hi everyone I have two queries have the same meaning but different results. Why is there a difference?. Queries are true? query 1: query 2:
0
votes
1answer
34 views

How to put marker on vector layer with lat/lon on QGIS [duplicate]

I have a vector layer, and bunch of lat/lon values. I want to put markers on the vector layer for each lat/lon pair. I have never used QGis, would you help with it. thanks.
0
votes
0answers
16 views

Is it possible to add XML data as DataStore inside GeoServer?

I have multi-polygon with feature information in xml Some kind like below: <polygon> <color>red</color> <coordinates> 125.94517419942997,37.080000000100085 ...
0
votes
3answers
75 views

ArcMap Change Values Greater than Standard Deviation of Mean to Zero

I have a feature class with greater than 1000 features and I would like to change all values greater than 2 Standard Deviations to a Zero. Seems like I could possibly use Field Calculator for ...
0
votes
1answer
38 views

How to edit a vector layer extent?

I'm working on QGIS 2.2, and I would like to make a vector layer extent bigger (thus the clip option is not suitable) to match exactly my mask layer extent. I would like the new added area to be ...
1
vote
2answers
68 views

How to convert Direction Of Travel OSM vectors from a “system” to another?

I have a painful doubt according Direction of Travel (DOT) vectors in OSM data. I'm using ArcGIS10, and a OSM data shapefile. I have a OSM road layer, that has many "Both ways" vectors and many "One ...
1
vote
1answer
63 views

label vector line with multiple attributes in QGIS

I have a line with two 2 attributes. I would like to display both information along with the line in frequent interval, one info above the line and the other is below the line. I am working in QGIS ...
0
votes
1answer
60 views

Issue clipping vector file with QGIS (geoprocessing tools)

I am trying to clip wind speed data (.shp format) to Canada's provincial boundaries (also .shp format). I am using the clip feature in vector > geoprocessing tools. For some reason the function always ...
0
votes
0answers
77 views

PyQgis: How can I “append” features to a Vector Layer instead of “stacking” them?

As I read data from a text file and add points to a QgsVectorLayer (as well as related attributes), each new record gets 'stacked' on top of the previous one in the Attribute Table (and within the ...
0
votes
1answer
44 views

TileStache can't find spatial ref for vector layer

I have a query based vector layer in my TileStache configuration, and it's hitting this block of code if layer.GetSpatialRef() is None and driver_name != 'SQLite': raise KnownUnknown('Couldn\'t ...
3
votes
2answers
331 views

Split Lines at Intersection of Other Lines

I have two line layers (roads and contours in this example) and I would like to split the roads layer every time it crosses/intersects a feature on the contour layer. I can't seem to find a tool that ...
1
vote
1answer
102 views

Iterating over selected features in QGIS Processing

I used to be able to iterate over selected features using the following script in v2.0. import processing features = processing.getfeatures(layer) for feature in features: #Do whatever you need ...
0
votes
0answers
34 views

How to set pen width of rivers based on scalerank attribute (QGis 2.2)?

I have a Vectorlayer from NaturalEarth.com with riverdata that includes "scalerank" information. Now I want to display these with different pen width based on their scalerank, like this: scalerank 1 ...
0
votes
0answers
20 views

Changing tracks to vectors in a grid

This is a version of a question that I posted on the GRASS list, but I didn't get any suggestions there. I would like to overlay a grid (cell size about 500 m x 500m) over an animal track created from ...