0
votes
1answer
48 views

Determining direction of longest segment of polygon?

I have a shapefile with 9000 agriculture fields and what I like to do is to determine for each field (=each polygon) the direction of the longest segment. For instance, the selected polygon in the ...
1
vote
2answers
24 views

How to extract a new linestring vector from a existing multipolygon in QGIS?

What I want to do: create a new line (named linestring in Postgis?) from existing multipolygon layer in Postgis. Purpose: once these lines are created, I'll run some distance calcs from specific ...
3
votes
0answers
13 views

Is there a limit to the number of polygon points you can export to CSV in QGIS 2.4?

Using QGIS 2.4 I am currently importing a csv file with ~30,000 polygons (polygons in WKT format). I also have a United States shapefile. I have used the Clip function to get only the polygons that ...
2
votes
1answer
25 views

How to subtract lines with thickness from polygon

I have a polygon and some lines crossing it. I want to subtract the lines with a certain "thickness" from the polygon, so it splits up into various polygons which do not touch each other anymore. You ...
0
votes
1answer
25 views

How to split Polygons by line grid?

I want to split a polygon by a intersecting line into different parts, exactly like in this post(Qgis - Is there a way to split a polygon layer with a line layer?). I have a vector grid to cut the ...
0
votes
2answers
51 views

Tool for rendering/drawing maps from coordinates

What tools can be used to convert a set of coordinates into polygons? For example: this code represents a room by providing information about it's four corners. <node id='-202' lat='41.015146' ...
2
votes
2answers
57 views

QGIS polygon centriods - How are they created?

I have been using QGIS to analyses spatial data and I created polygon centroids with the vector geometry tools. Now for a report I have to explain how these centroids were created. I have not been ...
0
votes
1answer
30 views

Cut polygon shapefile by line shapefile

I have two shapefiles, a polygon shapefile (lake) and a line shapefile (boudary) I want to create a new shapefile "polygon to the north of the boundary" What tool can I use in QGIS or other free ...
0
votes
0answers
17 views

Created polygon appears to move when zooming in (qgis)? [duplicate]

I am using QGIS 2.20 on a Windows 8.1 64-bit laptop. I have a shapefile that includes a polygon that I created from digitizing a Google Satellite image from OpenLayers Plugin. Here is my problem: ...
1
vote
0answers
17 views

Reclassify based in neighbour polygons

I would like to do a simple operation in QGIS and I am not sure about which is the best option. I have a polygon shapefile and each one has one class attached. I want to reclassify one of them based ...
4
votes
3answers
108 views

How to compute the outline of multiple tracks?

I have multiple gps tracks with depth data gathered from the lake. The tracks are overlapping/intersecting. I want to get an outline polygon. I have a multi-line shp. I've tried to diffuse it in qgis ...
0
votes
0answers
14 views

Create indicator for inclusion/exclusion from polygon based on coordinates, and reverse

I've got a database with 570,000 or so addresses, and what is purported to be their associated Lon/Lat coordinates. However, when I compare a simple scatter plot of these to the shape of a polygon ...
3
votes
2answers
63 views

“Levelling” elevation data coinciding with polygon?

I have a shapefile containing building geometries (polygons) and a elevation dataset. The elevation data doesn't perfectly match the buildings. I want to "flatten" the elevation data so that ...
1
vote
1answer
42 views

Smoothly interpolating Polygons from set of coordinates?

I'm still quite new to QGIS and I'm using it to display and analyze my soil data. I have point information on the distribution of the soils in a specific area and I need to create a soil map from ...
2
votes
1answer
33 views

Is there a way to clip a polygon layer according to DEM elevation?

I have a polygon layer on top of a DEM. Is there a way to clip the polygon layer according to elevation, ie the clipped result being only those areas of the polygon layer between x and y altitude? ...
-1
votes
0answers
31 views

what is the math behind rasterization? Doubt [duplicate]

In Figure 4 you can see how the overlap is not complete (marked with circles). What I would like to know which algorithm that QGIS uses the rasterization? What is your standard? Is there a percentage ...
1
vote
1answer
42 views

Get Coordinates of Voronoi Polygon Vertices [duplicate]

Is there any chance to get the exact coordinatas of the voronoi polygons? I am using Qgis software and I have the "center" (redpoint) of the polygons and I would like to export the polygons corners ...
0
votes
1answer
53 views

How to add point attributes to containing polygon?

I have three layers in a QGIS project: layer 1 is a boundary layer of polygons each with and id I will call "p_id" layer 2 is a point layer each with an id called "p_id" layer 3 is a .csv layer ...
0
votes
1answer
42 views

QGIS convert polyline to fixed width polygon

I have a shp file of polylines for trails, and I need to convert them all to be polygons that are 8 ft wide (4 ft from the center of each side of the polyline). I tried a following a few other posts ...
1
vote
1answer
44 views

Rectangle polygon is displayed as triangle

i am wondering why a rectangle polygon that i have created on an official german surveying website (downloaded as compressed shape in a zip-file) is displayed as a triangle when loaded in qgis. mighty ...
1
vote
1answer
61 views

How to close spaces within a polygon in QGIS 2.2?

I have a shapefile displaying the borders of several city units. One of its polygons, however, had free space consisting of four vertices in it. I created another polygon inside the free space and ...
0
votes
0answers
43 views

Draw polygon shape via Qbutton

Ideally; a Ui Qbutton is needed that will activate map canvas editing to add a polygon via the classic mouse click rubber band method. Upon a concluding right click with the active tool, editing ...
3
votes
2answers
88 views

Add rectangle polygon

I have a polygon shapefile layer. I want to add a rectangle polygon (just like in Arcmap), and another one using the previous polygon edge. I need it to be accurate, my hands do not meet this ...
0
votes
0answers
76 views

How to split an oblong, irregular polygon layer into even pieces?

I have a polygon layer (landuse) that I want to split into 100 meter pieces. The polygons show landuse along a road. I want to split the polygons layer so that I can then calculate the percentage of ...
4
votes
2answers
229 views

How to Polygonize a polyline shapefile in QGIS 2.2?

When I used QGIS 1.8, I was able to transform polyline layers to polygon layers with the Polygonizer plugin. In QGIS 2.2, this function has been subsumed into the Processing toolbox. Unfortunately, ...
1
vote
1answer
62 views

autocad-map of real estates with own coordinate system and information to be converted to use it in QGIS

I have a question regarding CAD and QGIS, but unfortunately I don't have a clue of CAD. Here it goes: Real estates data has been mapped. There are several reference points surrounding the area. So ...
1
vote
1answer
76 views

Intersect between polygonal shapefiles error

I'm encountering a problem when I try to intersect two different shapefiles. They are all new shapefiles I created to descibe the land cover and the land use of a city. The problem occurs when I ...
0
votes
0answers
31 views

Split/Erase/Differentiate polygon by polygon within a same layer

Is it possible to split a polygon with a polygon within the same layer in QGIS ? As in the image, i want the Polygon 2 to be split & the pointed area has to be retained as a separate polygon. ...
1
vote
1answer
57 views

QGIS: Clipping a line layer using a polygon and getting an empty shapefile

I am using QGIS 2.2.0 and want to clip a line layer (roads) so that only those inside a polygon are shown. When I do this using Vector->Geoprocessing Tools->Clip I only get an empty shapefile as an ...
1
vote
1answer
170 views

How to go with…somewhat complex geological maps in QGIS?

Just a follow-up to this question QGIS: Line to polygon conversion. Not sure do i have to continue there itself... We are currently digitizing a geological map...which has 36 features in total. Some ...
1
vote
1answer
70 views

QGIS: Line to polygon conversion

Currently we are working in a geological project..in which all the Contacts, Linear & some other geological features have to be captured. The thing is most of the features have to be Captured as ...
0
votes
2answers
60 views

merging shapefiles . an error occured during the merge operation

i am trying to merge multiple polygons of a feature. i select them via select features by polygon and use the advanced digitalizing toolbar " merge selected features" option. it worked for some but ...
1
vote
0answers
70 views

How do I smooth edges of polygons in QGIS?

Is there a built in function or plugin I can use to achieve smooth lines for my polygons instead of the blocky ones I have now?
1
vote
0answers
27 views

Entity handle from Visio

I have successfully imported the polygons from a Visio diagram via dxf into QGIS by using the "space" shape in Visio (a normal rectangular shape comes through as polylines, not as a polygon). Very ...
4
votes
3answers
128 views

How to shrink polygon on two sides?

I have a polygon which I know is a rectangle, although it may be at any orientation: I want to shrink this polygon by a third of the width from two sides, so that I just get the strip in the middle ...
2
votes
2answers
116 views

Simplify Multigeometry polygons in QGIS

I am really new to QGIS and KML so this might be obvious but I am too ignorant to know what to do. I have some KML files I would like to use in an application but they are much more complicated than ...
0
votes
0answers
29 views

QGis Filtering postgis layer with boundbox

I know It is possible to split a polygon feature by interactively drawing a line over it in QGIS 2.0 with the Split Feature command.The issue i have is that postgis layer i am trying to work on is ...
0
votes
0answers
42 views

Why does it take so long to run zonal statistics?

QGIS 2.0 Windows 7 I have pulled agricultural data from NASS CDL in tiff format. I want to track where a certain crop has grown over the years. My intention was to use a county shapefile overlaid ...
0
votes
0answers
33 views

Splitting polygon layer and joining attributes

I have two shape layers -- one a layer of counties in Florida and another a layer of MSAs in Florida. I would like to generate a new layer that has the following properties: MSAs that overlap more ...
2
votes
1answer
161 views

How can I filling ring in QGIS 2.2?

I created a polygon which covers a park. But I want to distinguish some small buildings located inside the park. Consequently, I want to distinguish them and use them as independent patches inside the ...
2
votes
3answers
175 views

How combine different geometry types into the same feature class

I've searched the question in this blog. Maybe I don't use the right words but anyway my problem is not present in any post so I'll try to explain my question by opening a new one. I have a polygon ...
1
vote
2answers
270 views

QGIS Valmiera, Labels only show for part of polygons

Using 2.2.0-Valmiera on Ubuntu 13.10 I have for Croatia 21 Counties as polygons. Labels show only for 12 counties: here I see that no labels are shown for multipart features. So I checked "Show ...
1
vote
1answer
48 views

Identify geographic location to points

I am quite new in QGIS and I really need your help. I have a map of Kenya divided into 68 districts and I have coordinates of 30.000 schools. The points have one variable besides the latitude and ...
5
votes
2answers
184 views

How to calculate the area between two line shapes?

I'm a newbie using QGIS (2.0). I'm trying to calculate the sidewalk area of a city. For that I have some shapes, extracted from Mricostation, with the topology (facades, fords, fences, etc.), but ...
0
votes
0answers
43 views

QGIS - Is it possible to Animate Polygons based on column values? [duplicate]

If you have an number of polygons with numeric data across 4 attributes/columns, you can display the data for one column but can you automatically cycle through the values for other selected columns? ...
0
votes
1answer
55 views

Can QGIS report/calculate areas/perimeters of individual polygon components within multipart shapefile?

Can QGIS report/calculate the areas/perimeters of individual polygon components within a multipart shapefile without using the "explode" vector tool to generate a new file? using QGIS 2.2.0 on ...
1
vote
1answer
114 views

Calculate distances between polygon centres in QGIS

Is there a practical way to calculate distances between polygon centroids in QGIS? I have a UK city region map divided into administrative units (1 ward = 1 polygon). I want to represent their ...
1
vote
1answer
49 views

How to automatically add identical new polygons to a layer?

I am seeking a way, using QGIS, to automatically add polygon features identical to others on the layer. In this case, they are water valves on a water network. Anyone know of a user-friendly way to ...
2
votes
1answer
151 views

QGIS - How can I convert a raster file to a vector file without making same value cells into one polygon?

How can I convert a raster file to a vector file without making same value cells into one polygon? In the attached image, the values "2124", "2269", "2321", "2634", and "2920" are the polygons ...
1
vote
0answers
46 views

Simplify by number of points in QGIS

I have a fairly simply question about something I just don't know how to do. I am aware you are able to simplify polygons in QGIS based on distance tolerance but my questions is, is there a way to ...