40
votes
Accepted
Getting polygon areas using GeoPandas
If the crs of the GeoDataFrame is known (EPSG:4326 unit=degree, here), you don't need Shapely, nor pyproj in your script because GeoPandas uses them).
import geopandas as gpd
test = gpd.read_file("...
- 53.8k
30
votes
Accepted
Calculating area in km² for Polygon in WKT using Python
It wasn't readily apparent to me how to use @sgillies answer, so here is a more verbose version:
import pyproj
import shapely
import shapely.ops as ops
from shapely.geometry.polygon import Polygon
...
- 1,188
28
votes
Calculate area for each polygon in R
You can do
library(raster)
x <- shapefile('file.shp')
crs(x)
x$area_sqkm <- area(x) / 1000000
Or with terra
library(terra)
x <- vect('file.shp')
x$area_sqkm <- expanse(x) / 1000000
That ...
- 9,991
23
votes
Accepted
How to calculate the polygon area and create a column of results in R
Can you provide data for an example? Anyways, try this:
library(sf)
f <- st_read("shapefile.shp")
f$area <- st_area(f) #Take care of units
Best
- 898
19
votes
Accepted
Calculate total area of polygons in shapefile using GDAL?
There's a special field in OGR SQL called OGR_GEOM_AREA which returns the area of the feature's geometry:
ogrinfo -sql "SELECT SUM(OGR_GEOM_AREA) AS TOTAL_AREA FROM myshapefile" myshapefile.shp
...
- 14.1k
19
votes
Accepted
Calculating area of lat/lon polygons without transformation using GeoPandas
Overview
Since version 0.7.0 geopandas has embedded the pyproj library as the crs object. pyproj, since version 2.3.0, has the ability to calculate the area of arbitrary polygons on a sphere. (see ...
- 1,557
15
votes
Accepted
Circle area calculation in QGIS is inaccurate
All recent versions of ArcGIS cheat -- the underlying shape type knows when it was generated as a circle, and reports a perfect circle area, even when the vertex count would make it an octagon.
I ...
- 19.7k
14
votes
Accepted
Using area() or $area function in QGIS, when the data (polygon) is stored in UTM?
The curved surface of the spheroid is unfailingly deformed when taken to the plane.
The planimetric area is not equal to the ellipsoidal area.
The differences, moreover, are not constant in a ...
- 13.3k
14
votes
Accepted
Why accurate area of all countries cannot be obtained using a single EPSG code, even if it corresponds to an equal-area projection?
What went wrong: EPSG:3395 is not equal area
The CRS you use, EPSG:3395, is definitely not an equal area projection. It is a World Mercator projection that heavily distorts areas, see here, including ...
- 61.1k
13
votes
How does ST_Area in PostGIS work?
SELECT
st_astext(col)
,st_area(col, false) AS area
FROM table
ST_Area(geometry) calculates the polygon area as WGS1984, WITHOUT ...
- 260
12
votes
Area is calculating wrong using $area in field calculator (QGIS 2.8.1-Wien)
Use area($geometry) instead of $area
According to the QGIS documentation, area($geometry) returns the area of a geometry polygon object. Calculations are always planimetric in the Spatial Reference ...
- 131
11
votes
Accepted
Calculating area of newly added polygons on same layer?
You can use the AutoFields plugin, which solves exactly that issue.
Go to the plugin's docked window, select your polygon layer, choose the 'Area' field from the list of existing fields, choose the ...
- 35.4k
11
votes
Calculating proportional area of polygon within another layer's polygon using QGIS
Take your model layer and in the attribute table, add a new field called area_mod for example.
Note that there are two ways to generate area:
$area is an ellipsoid based calculation using not just ...
- 10.3k
11
votes
Getting polygon areas using GeoPandas
Yes, simply be sure to reproject your shape in Cylindrical equal-area format with {'proj':'cea'} that preserve area measure.
Then you can use .area method of your GeoDataFrame.
Your also need to ...
- 111
11
votes
Calculate total area of polygons in shapefile using GDAL?
Yes, it is possible, but you need to use the OGR SQLite dialect as follows:
ogrinfo -dialect SQLite -sql 'SELECT SUM(ST_Area(geometry))/10000 FROM myshapefile' myshapefile.shp
Also, ensure that ...
- 4,862
11
votes
Calculating percentage of overlap of two layers in QGIS 3
Since QGIS 3.8, it's now included in QGIS core, without plugin or coding.
In the Processing Toolbox, search for Overlap and open the Overlap analysis:
Source: http://changelog.qgis.org/en/qgis/...
- 6,921
11
votes
Calculating area of polygons without script in QGIS Field calculator
There are two tabs under the field calculator - Expression and Function editor, i suppose you're referring to the function editor tab which requires coding skills.
If you stay on the Expression tab ...
- 5,693
11
votes
Accepted
Deleting parts of MultiPolygon based on area using PyQGIS
You can make a new part list from the MultiPolygon instead of deleting the parts.
layer = iface.activeLayer()
# Minimum area threshold
minimum_area = 2000
layer.startEditing()
# Loop through all ...
- 72.5k
10
votes
Calculating area in km² for Polygon in WKT using Python
The other answers seem to be correct, except that at some point, the lat1 and lat2 parameters in the pyproj code were renamed with underscores: lat_1 and lat_2 (see https://stackoverflow.com/a/...
- 203
10
votes
Calculating polygon areas in shapefile using QGIS
If not getting very accurate area calculations does not bother you (or if you do not want to play with different options in the field calculator as mentioned by some of the answers and comments above),...
- 463
10
votes
Accepted
Deleting polygons smaller than certain dimension using ArcGIS Desktop?
Use my script from Checking if polygon fits inside another polygon using ArcGIS or QGIS?
to create points inside your polygons. Each point is a centre of maximum inscribed circle of the parcel.
...
- 22.4k
10
votes
Selecting polygon with the largest area in QGIS
You would be better off using "Select by expression" instead of "Select by attribute". Your expression should be something like:
"AREA" = maximum("AREA")
...
- 1,976
10
votes
Accepted
How does $area function calculate area in QGIS?
Function $area:
Returns the area of the current feature.
The area calculated by this function respects both the current project's ellipsoid setting and area unit settings.
For example, if an ...
- 13.3k
10
votes
Calculating percentage of overlap of two layers in QGIS 3
Using a "Virtual Layer" through Layer > Add Layer > Add/Edit Virtual Layer....
Let's assume there are two overlapping polygon layers called 'LayerA' (brown) and 'LayerB' (grey), see ...
- 28.9k
10
votes
Accepted
$area gives NULL for some polygons in QGIS's Field Calculator
Short Answer
you have to re-project the shapefile to EPSG:3148 - Indian 1960 / UTM zone 48N
Long Answer
Load the shapefile
Left click the shapefile in Layers pallet
Go to Export > Save feature as
...
- 704
10
votes
Calculating polygon area in QGIS without adding new field
The identify tool does offer you this information.
Click any feature, then expand the topmost dropdown menu. Here all basic geometric information is hidden, incl. the area and circumfence.
- 15.1k
10
votes
Calculating polygon area in QGIS without adding new field
Create a label with the expressin $area (I should have used round($area)):
- 63.9k
9
votes
Calculating polygon areas in shapefile using QGIS
Try using the "Identify Features" tool (Ctrl+Shift+I) from the Attributes Toolbar.
There will be two attributes: "Area (Cartesian)" and "Area (Ellipsoidal - EPSG:7019)"
...
- 28.9k
9
votes
Calculating area of newly added polygons on same layer?
There are 2 approaches:
1/ select all area's which has no value ("Area" is null) and do the calculation just on the selected ones. Check 'only update XXX selected features' and 'update existing field'...
- 5,207
9
votes
Getting polygon areas using GeoPandas
I believe yes. The following ought to work:
gdf['geometry'].to_crs({'init': 'epsg:3395'})\
.map(lambda p: p.area / 10**6)
This converts the geometry to an equal-area projection, ...
- 1,145
Only top scored, non community-wiki answers of a minimum length are eligible