30
votes
Accepted
Why is ellipsoidal distance greater than cartesian distance?
Cartesian distance is as measured on a flat Earth. Ellipsoidal distance is as measured on a spherical shape (or ellipsoid). To understand why the latter is longer, draw a circle and then draw a ...
- 33.6k
16
votes
Creating square polygons of given length from single corner point in QGIS
There is "Vector geometry > Geometry by Expression" tool in Processing Toolbox. You should use in a projected coordinate system.
Select "Polygon" as "Output geometry type&...
- 74.6k
15
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 ...
- 63.1k
14
votes
Using measuring tool in ArcGIS
The measure tool does not need any extension. However, the coordinate system of the data frame needs to be defined before you can use it. right-click on the data frame to set its properties.
- 49.3k
12
votes
Accepted
Calculating semi-major and semi-minor axis length of an ellipse in QGIS
Processing Toolbox -> Vector geometry -> Oriented minimum bounding box tool may be another solution. This tool already generates the width and height of the bounding boxes.
Half of both will ...
- 3,369
12
votes
Accepted
Creating square polygons of given length from single corner point in QGIS
Use geometry by expression to create a point at 315 degrees azimuth from your point with a distance of the hypotenuse of the square, then create a box around the two points:
bounds(collect_geometries( ...
- 67.1k
11
votes
Accepted
Calculating length of each polygon side in PostGIS
See: https://stackoverflow.com/questions/7595635/how-to-convert-polygon-data-into-line-segments-using-postgis :
SELECT st_length(ST_MakeLine(sp,ep))
FROM
-- extract the endpoints for every 2-point ...
- 67.1k
11
votes
Accepted
Generating lines at the end of each measurement with plugin in QGIS
Coming close to what you want, simply using geometry generator, you can use this expression to create the lines from each point to the cursor position where you click:
make_line (
$geometry,
@...
- 63.1k
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 ...
- 13.4k
10
votes
Why accurate area of all countries cannot be obtained using a single EPSG code, even if it corresponds to an equal-area projection?
In addition to the fact that EPSG:3395 is not an equal area projection (therefore inaccurate for area measures), as mentioned by @Babel, a precise measure of the area requires a good projection. ...
- 49.3k
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.
- 15.5k
10
votes
Calculating polygon area in QGIS without adding new field
Create a label with the expressin $area (I should have used round($area)):
- 67.1k
8
votes
Accepted
Calculating polygon area in QGIS without adding new field
I personally find the identify tool sometimes too clunky. Here another approach:
To show the area for a polygon without using an additional field, you can just use a formula for a label with the $area ...
- 3,221
7
votes
Calculating semi-major and semi-minor axis length of an ellipse in QGIS
Use Menu Processing / Toolbox / Minimum bounding geometry / Minimum Oriented Rectangle. Than the values you look for correspond to half of the sited of the rectangle.
Edit: as described in @Kübras ...
- 63.1k
6
votes
Measuring distance between points in QGIS
Another option from mentioned by @Spacedman is the following:
Connect target points with the source point (observation one)
Measure distances for created lines
This option could also help you to ...
- 752
6
votes
Accepted
Measuring between points in QGIS
I don't think there is a plugin for that. But with a little sql, you can calculate it.
If predecessor is defined by their id, then you can execute following code in the databasemanager:
select
a. ...
- 5,237
6
votes
QGIS under measuring distances
That is happening because:
You are drawing planimetric lines in a Mercator projection far away from its true scale curve (the equator in EPSG:3857);
And the Mercator projection produces ...
- 13.4k
6
votes
Сreating buffer in meters using GeoPandas
Yes you need to reproject into a coordinate system with meters as units.
import geopandas as gpd
df = gpd.read_file(r'C:\GIS\data\tempdata\points_wgs84.shp')
df = df.to_crs(3043) #Pick another
df['...
- 67.1k
6
votes
Generating lines at the end of each measurement with plugin in QGIS
You would probably need to create a custom map tool. For starters read about using the map canvas and creating map tools at the PyQGIS developer cookbook at https://docs.qgis.org/3.28/en/docs/...
- 4,824
5
votes
Measuring distance between points along line in QGIS
I first thought this question was basically same as another recent question Points layer distance from the start of line layer in QGIS.
However, there is an added complexity in this one, that OP ...
- 30.4k
5
votes
Accepted
Deactivate Snapping for Measure Maptool (mActionMeasure) in QGIS temporarily
We could create a function whereby:
If the mActionMeasure button is checked, the snapping mode is turned Off
If the mActionMeasure button is unchecked, the snapping mode is turned On
Here is the ...
- 75k
5
votes
How to calculate the mean distance between co-ordinates in QGIS
To find statistics on the nearest neighbors, you would go to Vector > Analysis tools > Nearest Neighbor Analysis. Upon completion, it displays a window that includes the mean distance. Make sure ...
- 39.7k
5
votes
Measuring distance between points in QGIS
Put your observation point in a point layer and use "Distance Matrix" from the Vector... Analysis Tools menu.
Make sure there's a unique ID column in your layer of points. I've got one point in the "...
- 61.5k
5
votes
Accepted
PostGIS Geometric V Geography measurements when using ST_Length
EPSG:3857 is also known as Web Mercator.
Usual Mercator projections preserve angles but creates important distortions of size. Web Mercator has slight distortion of angles.
Web Mercator shares some ...
- 2,077
5
votes
Accepted
Calculating distance between multiple associated points in QGIS
It's possible to do that from your XY coordinates.
First you should create a table join between your list A to list B (this way because of 1 farmer per farmstead. it's a left join). Then create a new ...
- 2,191
5
votes
Finding length and width of regular/irregular polygons in QGIS
Try Minimum bounding geometry:
Height and width attributes in output. You can join them back to the original data using id column.
- 67.1k
5
votes
Finding length and width of regular/irregular polygons in QGIS
You can use the Field calculator to find the with and length of the equivalent rectangle solving quadratic equation:
Perimeter = 2 (a + b)
Area = a * b => a = Area / b
Substitute a into the first ...
- 7,112
5
votes
Accepted
Measure distance in km of polyline in QGIS
Create a new field with field calculator and this expression $length/1000.
This was the short answer. More details in what follows, as things are a bit more complicated.
How to calculate length? Use ...
- 63.1k
5
votes
Automatically updating feature area in the attribute table using QGIS
Let's assume there was created a feature and calculated an "area" attribute for it
For catching changes done to that feature i.e. automatically updating the area, please set up some ...
- 29.9k
5
votes
Finding mean distance between cluster center and points in cluster in QGIS
On the layer with the center point, you can use QGIS expressions. Get an array of the points from the same cluster using array_foreach and then for each of these points create create a line to the ...
- 63.1k
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