All Questions
65
questions
1
vote
1
answer
48
views
Calculate ratio of 2 polygons using QGIS modeler
Working with QGIS modeler, I need to do some arithmetic operations with some polygon areas.
Let's say there are 2 polygons in layer A and layer B. And I'm inputting them into the model using Vector ...
- 123
1
vote
0
answers
83
views
QGIS ellipsoidal area values changing very slightly between calculations while planimetric values stay the same
I have a number of vector shapefiles that I need to calculate the geodesic/ellipsoidal area for. These shapefiles are accessed and updated regularly, with the area recalculated each time they are ...
- 57
1
vote
2
answers
67
views
QGIS Count values between two numbers inside a polygon in another layer
I have 2 layers.
LayerA are multiple polygons of the area that i'm evaluating (Red boundarys).
LayerB is a MSAVI raster to vector with the data (multicolor greens - blues).
I want to calculate the ...
- 87
0
votes
1
answer
74
views
Adaptive polygon division in QGIS
Let say I have an irregular polygon layer that I want to divide into squares of fixed size (i.e. 50 x 50m). The simplest solution is to create a grid based on the polygon extension and then use the ...
- 47
4
votes
1
answer
99
views
Add polygon areas by roof orientation condition
I have a shapefile with building poligons and a raster file with the roof orientation (0-360º). I would like to assign the orientation to the building shapefile using QGIS. I converted the raster file ...
- 309
4
votes
1
answer
169
views
Why area of intersection differs from total area of polygon?
I calculated intersection between Layer 1 and Layer 2 using expression below:
area(
intersection (
$geometry,
collect_geometries(
overlay_intersects ('layer1',$...
- 155
2
votes
1
answer
75
views
Merging all polygons (and their respective attributes) into similar areas in QGIS
As you can see in the image, I'm trying to merge selected polygons and their respective attributes. I have thousands of these polygons (some very small, others very large). I have to create areas of ...
- 21
3
votes
1
answer
142
views
Create competing polygons from points and bearings (azimuth)
I have a set of points on a city, representing CELL TOWER locations. Each CELL TOWER has 3 or 4 different CELL RADIOS pointing to diferent directions (Azimuth). What I need is an algorithm to take ...
0
votes
1
answer
709
views
QGIS calculate area automatically
Is there a way to calculate area automatically when I edit a polygon? I mean, is there any function there I can use on area field and update itself when I finish editing?
- 671
3
votes
2
answers
268
views
Calculate the percentage of a polygon either side of a line
I have a series of polygons outlining distributions of various fish species around Australia. I am relatively new to GIS.
I am trying to class each species as either tropical or temperate based on the ...
- 41
1
vote
1
answer
103
views
Calculating area's region in DEM
I have a DEM map in my project Tsunami Assesment project.The white area below the mentioned map is sea and we know that possible tsunami height is 14 meters(please neglect the line, there is an error ...
2
votes
1
answer
208
views
Calculating cumulative sum of area values in attribute table by graphics in QGIS
In QGIS I have a set of polygons divided into plots, each polygon has a diameter and area. I would like to sum up the polygons per each plot area.
From the attribute table, the polygons are not ...
- 69
0
votes
1
answer
150
views
How to get a list of the empty areas between the filled ones? (+size in ha)
I am an absolute beginner in GIS software.
My goal is to get a list (or something similar) of all the empty polygons/areas between the colored ones. It would be perfect if the size and location of the ...
- 140
1
vote
0
answers
73
views
Calculating area of polygon with consideration of slope in QGIS [duplicate]
I would like to know if there is an easy/efficient way in which you can calculate the area of a polygon considering the irregular slope underneath the polygon. I would like to know a solution in QGIS.
- 615
3
votes
1
answer
557
views
QGIS 3.8.3 - Create polygon with a specific width
I'm very new to GIS and QGIS.
I'm trying to map areas of arable fields and would like to create a polygon that traces the edge of a field and is a specific width away from the edge of the field ie 8 ...
- 33
3
votes
1
answer
247
views
Creating field with difference between areas of two layers in QGIS
In QGIS how can I get the difference between the areas of two layers through field calculator? And is there a way to automatize it so every time a new feature is added the difference updates?
Layer 1 ...
- 1,092
4
votes
5
answers
2k
views
Calculating polygon area in QGIS without adding new field
Is it possible in QGIS to quickly calculate the area of a polygon using a Processing tool, plugin, script without adding attributes or creating a new layer?
Something launching the results window or ...
- 87
2
votes
2
answers
410
views
Calculating how much of polygon is within certain boundary in QGIS
I work for a local authority and I'm measuring the surface area of river catchments inside our local authority.
I have a polygon layer showing me the catchments but a few of them go over our boundary ...
- 21
3
votes
2
answers
360
views
Performing area weighted interpolation in QGIS
I have encountered a problem that I thought would be much more simple than I see it actually is, and conventional clipping did not work.
I have the following grid layer with different values of a ...
4
votes
1
answer
195
views
Calculating area of polygons without script in QGIS Field calculator
Whenever I click the Field Calculator in the attribute table, I am prompted to created a script in order for it to calculate the area of a polygon. However, I do not want to use code in obtaining a ...
- 41
1
vote
0
answers
183
views
Polygon area calculation returning 0.0 QGIS
I am trying to calculate the areas of these 12 individual polygons.
However, when I run the area calculation, two of the polygons return 0.0 - whereas the calculation works for the other 10?
Why is ...
- 199
2
votes
1
answer
361
views
Compare two layers and find the percentage of the shared areas that are different between them
I have two shapefiles that identify flood zones for the same general area but in different years. The maps, however, do not cover exactly the same geographical areas (e.g., shapefile 1 covers counties ...
- 301
3
votes
1
answer
582
views
Finding area of polygons within buffer [duplicate]
I have 102 different sites in two cities, which I have created buffer zones for.
I also have layers that have polygons for different landscape features (e.g. water surface area).
I am trying to find a ...
- 31
1
vote
1
answer
109
views
Adding shapes to polygon feature in the same row
I've got somehow simple issue but cannot process it.
I am working with shapefile in QGIS (3.10 on MacOS), where having several polygon features stored as rows. I want to somehow (manually) edit some ...
- 111
5
votes
2
answers
1k
views
Intersecting area between two polygons in the same shapefile in QGIS
I have a shapefile with two polygons in it. I would like to be able to generate the intersecting area between the two polygons.
Please note, I have tried using the intersect tool, however this does ...
- 241
6
votes
3
answers
482
views
Calculating proportional area of polygon covered by circle [closed]
I have two layers here (ignore the green layer), blue polygons and black circles. I want to calculate for each circle, what percent of the each of the blue polygons does it cover. For example, the ...
- 449
1
vote
1
answer
79
views
QGIS - Inaccurate field calculator
When I retrace a polygon using the measure area tool and get what I believe to be an accurate area measurement. However if I utilise the field calculator within the attribute table to calculate the ...
- 13
1
vote
0
answers
55
views
Grouping of polygons or overlaying layers in same shapefile? Problems calculating the correct polygon areas
I am having trouble calculating polygon areas of my shapefile. When opening the shapefile in QGIS it seems like there are multiple polygons overlapping within the same shapefile or that polygon areas ...
- 61
3
votes
1
answer
1k
views
Calculated area is too large using Field Calculator in QGIS
When I run the Field Calculator to update area, the resulting areas are too large. This happens whether I use QGIS 2.18 or QGIS 3.4.
The default CRS is set to: ESPG:27700, OSGB 1936 / British National ...
- 143
3
votes
3
answers
2k
views
Summing area of polygons within vector layer within zone using QGIS
I have one vector layer with multiple polygons (purple). I also have a number of other vector layers which are catchment zones (I also have a layer where these catchments are merged).
Is there any way ...
- 101
1
vote
1
answer
1k
views
Processing area and calculating volume of polygon with know elevation from DEM in QGIS
I got a DEM of a watershed and I need to create a dam at a fixed elevation (with a rectangular polygon corresponding at the top of the dam) and calculate it's area (including the slope (fixed value) ...
- 49
2
votes
0
answers
598
views
Calculating the area of raster within polygon
I have a raster layer with values of energy demand in each cell. I would like to know the area of the raster within each polygon (see screenshot). Any suggestions on a simple approach for this?
- 181
0
votes
1
answer
1k
views
Calculating area under each polygon in QGIS [duplicate]
I would like to know how to calculate the area of the vector layer (red in the photo) under each polygon (white square in the photo). The red layer has the area (km2) in its attributes. But what I ...
- 21
2
votes
3
answers
5k
views
Calculating polygon area within polygons in QGIS
I want to estimate the area of the reef under a polygon grid.
My shapefiles are already in meters, however I am having a hard time calculating the area under the grid layer. Attached are the photos.
I ...
- 21
1
vote
1
answer
345
views
Area difference between polygon layers
I would like to calculate the difference of area between two polygons. I tried using the Difference tool, but all it does is create lines that are different between my two polygons. I also tried the ...
- 63
2
votes
1
answer
769
views
Selecting polygons which contain majority of area from intersected layer by polygons using QGIS?
I have two polygons layers (a squares grid (blue in image) and a rectangles grid (green in image)). Because the different polygon sizes, different squares overlap with a single rectangle. I need to ...
- 23
2
votes
2
answers
2k
views
Area of Intersection between two polygon files in QGIS
I'm new to mapping concepts and software.
I need to report on the intersecting area of postcode polygons and NBN Rollout areas. So postcode 3000 has 3 units of area in rollout region 1 and 6 units of ...
- 21
4
votes
1
answer
972
views
Why the outcome of $area (geometry), is different from area saga shape indices tool in QGIS?
I am puzzled on why I get different outcomes on trying to calculate the area (m2) for multiple polygons in QGIS.
My polygons consist of tiny objects of few cm extent.
When using $area (field ...
2
votes
2
answers
5k
views
Polygon in specific size
I have the task of inserting a polygon in a map with a specific size. My idea is to simply "draw" a polygon and keep on enhacing its size, until it reaches the size I actually want to be. Its ...
- 557
2
votes
1
answer
241
views
QGIS Aggregate function missing
I want to sum the areas of several polygons in the same shape layer by using the Aggregate function in Select features using an expression. However, I can't find the Aggregate menu nor the SUM ...
- 33
0
votes
1
answer
3k
views
Getting area of polygons in QGIS [duplicate]
I have a world map divided into zones and need to compute the area for each polygon. I tried using Vector > Geometry Tools > Export/Add geometry columns and successfully get the area and perimeter but ...
- 69
1
vote
1
answer
62
views
Calculate areas of each soilscape type per boundary
I would like to do the following:
Get the area of each soilscape type
Calculate the sum of area per boundary
I'm trying to do the following but seems the output is always "0"
- 13
6
votes
1
answer
288
views
Calculating Statistics Based on Expression in QGIS?
Is it possible to calculate the sum of polygon areas based on whether or not it has a value in another column?
For example:
In column 2 I have the area of polygons. I want to calculate the area of ...
- 385
2
votes
1
answer
4k
views
Calculating polygon area inside another polygon in QGIS
Is it possible to calculate the area of colorful polygons (yellow, yellowish/reddish and red) inside another shapefile (purple outline, also polygons) in QGIS.
For example the polygon that is marked ...
- 91
4
votes
2
answers
8k
views
Displaying unit as 'text' within label in QGIS?
When labelling areas in QGIS I can't figure out how to display the unit after the number value from a field.
For example the area of my polygon might be 1.23 hectares, which has been calculated ...
- 41
1
vote
0
answers
250
views
Calculating area of polygons in EPSG:102022 in QGIS?
I am trying to calculate the areas of administrative regions in Uganda, using the EPSG:102022 projection. They are polygons. But everything I do produces areas in degrees rather than meters, giving ...
4
votes
1
answer
2k
views
Selecting polygon with the largest area in QGIS
I would like to select the largest number in a column of an attribute table by "Select by attributes" in QGIS to select the polygon with the largest area. How would be the expression for ...
- 181
2
votes
0
answers
507
views
Calculating area of voronoi polygons from real life data using QGIS?
I have an area, which I divided into voronoi polygons using data points. I have no problem creating the polygons.
Now the data points are on a coordinate system, where every degree represents one ...
- 21
1
vote
1
answer
2k
views
Area measurement in QGIS
I try to measure a polygon with Export/Add geometry columns tool. The units for area measurement are square meters.
The problem is that I get different area results for the polygon:
When the ...
- 4,072
10
votes
2
answers
9k
views
Calculating proportional area of polygon within another layer's polygon using QGIS
I have two polygon layers, 'model' and 'ntem', whose features overlap and intersect one another.
I would like to calculate the proportion of the area of the 'model' polygons which fit within each '...
- 497